finding peak piston velocity in terms of crankshaft degree

How would one go about doing this? is there apoint where its always the fastest?

How would one go about doing this? is there apoint where its always the fastest?
A shorter rod will cause the piston to travel within the bore at a faster rate [higher load rate]. A longer rod will slow piston velocity within the bore, and it will increase dwell time at TDC and BDC.
The change in direction at the top of the stroke and bottom of the stroke is where the Volicity is quickest..yes?? No??
Is this what your after?

A shorter rod will cause the piston to travel within the bore at a faster rate [higher load rate]. A longer rod will slow piston velocity within the bore, and it will increase dwell time at TDC and BDC.
The change in direction at the top of the stroke and bottom of the stroke is where the Volicity is quickest..yes?? No??
Is this what your after?


how is peak velocity slower with a shorter rod.

if both start at the same, and end at the same time- and one "stops" for a longer period time...

wont average speed be the same but peaks be different- with the longer having a higher peak?

is peak piston velocity right after and before TDC?

how is peak velocity slower with a shorter rod.

?
Thats not what I typed:
Originally Posted by Hot Rod Hawk
A shorter rod will cause the piston to travel within the bore at a faster rate [higher load rate].

im thinking max speed will be a couple dgrees BTDC and BBDC...not positive.

it has been discussed here before.

found this statement by rich...

With a 350 Chevy, switching to 6" rods from 5.7" ones will delay peak piston velocity
from 74.5° to 75.5°.
Rich

but wouldnt you have that same point of velocity every 90 degrees after that?

im just trying to visualize it in my head(not an engineer or anything!)

im probably WAY off base here though!

I'm thinking peak velocity of the piston occurs when the rod angle to the
piston is at the greatest point, and the crank angle is approaching 90
degrees with respect to the perpendicular of the cylinder bore.

At TDC and BDC, the piston is only moving tiny amounts as the crank throw
and connecting rod are inline with the cylinder bore (parallel)

How would one go about doing this? is there apoint where its always the fastest?

1) Why do you want to know, other than curiosity? Average piston speed is usually a benchmark for engine durability or even "doablity". It isn't affected by rod length, where max. piston speed is.

2) Max Piston velocity doesn't occur at 90 crank position with a finite rod length. Imagine a 1 mile long rod. It would have very little angularity on a 3.50 stroke engine throughout the stroke, so max. piston velocity would occur nearly at 90 and 270 degrees if TDC was 0 degrees. Now imagine a zero length rod. Yeah, it won't work, but the piston velocity would be constant at the velocity of the center of the rod journal.

3) It's a simple(?) geometric relationship of crank throw and rod length. The spreadsheet has been posted previously. Try searching.

4) When BMW revealed data on the P83 F1 engine they said peak piston speed was 45 m/s (@19200 revs) and mean was 25 m/s. That allows you to back into rod length once you figure stroke length.edited: Peak P/S was 40 m/s, not 45. Thanks folks for pointing out the error. 45/25 does couse some satrange engine parameters. :)

1) Why do you want to know, other than curiosity? Average piston speed is usually a benchmark for engine durability or even "doablity". It isn't affected by rod length, where max. piston speed is.

2) Max Piston velocity doesn't occur at 90 crank position with a finite rod length. Imagine a 1 mile long rod. It would have very little angularity on a 3.50 stroke engine throughout the stroke, so max. piston velocity would occur nearly at 90 and 270 degrees if TDC was 0 degrees. Now imagine a zero length rod. Yeah, it won't work, but the piston velocity would be constant at the velocity of the center of the rod journal.

3) It's a simple(?) geometric relationship of crank throw and rod length. The spreadsheet has been posted previously. Try searching.

4) When BMW revealed data on the P83 F1 engine they said peak piston speed was 45 m/s (@19200 revs) and mean was 25 m/s. That allows you to back into rod length once you figure stroke length.



i want to know out of curriousity, but not just for ****s and giggles.

Obviously, you want to relate camshaft events to the peak timing. Ideally, youd have your cam peak (if thats where the heads flow best) when the piston was at max velocity, no?

iObviously, you want to relate camshaft events to the peak timing. Ideally, youd have your cam peak (if thats where the heads flow best) when the piston was at max velocity, no?


I looked at the intake port velocity in an EA Pro simulation of an LT1 with a custom cam. The intake port velocity peaked just about 90 degrees ATDC. This didn't vary a lot from 3000 to 6600. The peak piston velocity is about 75 degrees ATDC, remember.

On this particular engine, peak velocity at 3000 rpm was about 300 fps, but it also had a -100 fps reverse flow as the intake closed late. By 6600 the peak was up to about 500 fps and there was no reverse flow indicated. This cam was designed to peak torque around 5000 and have a fairly flat hp peak from 6000 to 6500, so it was optimized for that. At 6400, when the piston velocity was zero at BDC on the intake stroke, the intake velocity was still over 300 fps!

I wish I could post the graphs.

My take is that because the air has mass and takes a finite time to accelerate, the air velocity always lags behind the piston position which is creating the pressure drop which gets the air to flow. The up side is that the air slows down slower than the valve closes at higher rpm and packs itself into the cylinder near intake valve closing point.

This is all NA, of course.

If you e-mail me the graphs I'll post them up on my site and link them here for you... :)

I looked at the intake port velocity in an EA Pro simulation of an LT1 with a custom cam. The intake port velocity peaked just about 90 degrees ATDC. This didn't vary a lot from 3000 to 6600. The peak piston velocity is about 75 degrees ATDC, remember.

On this particular engine, peak velocity at 3000 rpm was about 300 fps, but it also had a -100 fps reverse flow as the intake closed late. By 6600 the peak was up to about 500 fps and there was no reverse flow indicated. This cam was designed to peak torque around 5000 and have a fairly flat hp peak from 6000 to 6500, so it was optimized for that. At 6400, when the piston velocity was zero at BDC on the intake stroke, the intake velocity was still over 300 fps!

I wish I could post the graphs.

My take is that because the air has mass and takes a finite time to accelerate, the air velocity always lags behind the piston position which is creating the pressure drop which gets the air to flow. The up side is that the air slows down slower than the valve closes at higher rpm and packs itself into the cylinder near intake valve closing point.

This is all NA, of course.

now my question is- why 75* ATDC and is it like that for every computer

now my question is- why 75* ATDC and is it like that for every computer

It's all about the geometry of the rod length and the stroke. The longer the rod, the less rod angularity you have so the closer Vmax occurs to 90* from the bore centerline. In the range SBC has for stroke and rod/stroke ratio, the Vmax point will float around 75* no matter how you calculate it.

I'll try a F1 BMW engine when I get a chance.

Reread this and see if it helps visualize what's happening:

"Max Piston velocity doesn't occur at 90 crank position with a finite rod length. Imagine a 1 mile long rod. It would have very little angularity on a 3.50 stroke engine throughout the stroke, so max. piston velocity would occur nearly at 90 and 270 degrees if TDC was 0 degrees. Now imagine a zero length rod. Yeah, it won't work, but the piston velocity would be constant at the velocity of the center of the rod journal."

I jsut did some quick math using the only geometry I remember from middle school- the Pythagoreum Theorum (sp?). You know.... A squared + B squared = C squared. Solve for the piston location when the rod and crank throw are at 90* to eachother.

For a production 350...

A = 1/2 the stroke length (3.48 / 2 = 1.74")
B = rod length (5.7")
C = *the result* how far up the piston (wrist pin centerline) is from the crank centerline

let's see..... this goes here..... that goes there........................... carry the one........... sqare root is.................

Piston wrist pin will be 5.96" above the crank centerline when the crank throw is 90* to the rod. Thank you, thank you. I'll be here for your entertainment all week. Now for my next amazing trick....

At TDC using the same scenario the wrist pin will be 7.44" above the crank centerline (1.74 + 5.7 = 7.44). At BDC the piston will be 3.96" above the crank centerline (5.7 - 1.74 = 3.96).

The "halfway" point between the two would be, obviously, 5.7" above crank centerline (when the crank stroke is 90* to the bore centerline). But the point at which the crank stroke is 90* to the ROD, must happen before that...... and (amazingly) my math shows that. 5.96 > 5.7.

Now, I don't know how to reverse-calculate crankshaft angle at that point, but I'm sure somebody does (and I'd love to know). So instead I went downstairs and mocked up the whole mess with some wire cut to length and a t-square. Then I broke out my protractor and measured the crank throw angle relative to the centerline of the bore at that point.

IT'S A MIRACLE!!!!!! I'm measuring somewhere close to 75* ATDC is where the rod goes 90* to the crank throw. More that that, a longer 6" rod doesn't make much difference in that angle. The rod length is HUGE compared to 1/2 the crank's stroke and so a little .300" bump in rod length doesn't make any noticable difference on the crank angle at which the rod is 90* to the crank throw.

I'm going to take a nap. I have a math hangover now.

4) When BMW revealed data on the P83 F1 engine they said peak piston speed was 45 m/s (@19200 revs) and mean was 25 m/s. That allows you to back into rod length once you figure stroke length.

Wouldn't that be like having an under 1 to 1 rod stroke ratio? To get Max/Mean piston speed to that ratio I have to get extremely short on the rods!

(45 m/s)/(25 m/s) = 1.80

To get that ratio of max piston speed to average or mean piston speed on 4 inch stroke BBC I would have a 3.70 inch rod! That would net me say at 7000 rpm a max piston speed of 8385 FPM and a mean piston speed of 4667 FPM for a ratio of the same 1.80 of max vs mean piston speeds.

I think that F1 data is a misprint!

Also at that 1.8 max/mean ratio which is also around .93 R/S ratio you would have peak piston speed at around 65 degrees ATDC. Of course the pistons and crank would never clear with this setup but just saying if it did! At 9.800 deck height you could run over 4 inches of compression height on your piston though so you could run one hell of a dish for your turbo!!!

I know people that build F1 engines and I think they are more like 2.5 R/S ratio due to packaging of the heads and the V-angle? The 90 degree stuff allowed the rods to be shortened substantially over the old 72 degree stuff.

This rod ratio (2.5 to 1) would allow peak piston speeds around a 1.60 max/mean ratio or 40 M/S which is more likely if the average was 25 M/S?

Just read the Renault thread and it was a misprint I guess! I was really wondering there for a second Old Stroker!

Wouldn't that be like having an under 1 to 1 rod stroke ratio? To get Max/Mean piston speed to that ratio I have to get extremely short on the rods!

(45 m/s)/(25 m/s) = 1.80

To get that ratio of max piston speed to average or mean piston speed on 4 inch stroke BBC I would have a 3.70 inch rod! That would net me say at 7000 rpm a max piston speed of 8385 FPM and a mean piston speed of 4667 FPM for a ratio of the same 1.80 of max vs mean piston speeds.

I think that F1 data is a misprint!

Good catch Eric. The typo was mine. Peak piston speed was quoted by BMW at 40 m/s, not 45 as I said above. Sorry. 1.6:1 peak/avg is more believable, huh?

The also said "air intake volume" was 1995 cubic meters/hour or about 1174 cfm.

See Racecar Engineering V13 No.12 (Dec 03).

FWIW, using the 19200 peak rpm, 40 m/s peak piston speed and 25 m/s avg. piston speed on a 10 cylinder engine of just shy of 3000 cc, I got the following:

Stroke:
39.065 mm (1.538 in.)

Bore: 98.75 mm (3.888 in.)

Displacement: 2992 cc

Rod length: 98.0 mm (3.858 in. )

R/S ratio: 2.51:1

I get peak piston speed at about 80* ATDC

Rod length calculation is very sensitive to peak piston speed, so it's only a close approximation. I assume that BMW may have rounded off the p/s numbers a little just to keep us guessing.

Yes but they're all around there. 5000 FPM or so. They make real power higher but the friction curve drops the actual power down to that FPM.

Yes but they're all around there. 5000 FPM or so. They make real power higher but the friction curve drops the actual power down to that FPM.

Another take isn't necessarily friction hp, but the ability to live for a race.
I think you'll find that most endurance race engines like F1 and Nextel Cup which run maybe a million+ revs between teardown/replacement are right around the 5000 fpm mark you mentioned. Cup a little higher, F1 a little lower. That PS limit hasn't moved up a lot in the last years. Mainly strokes have been coming down. 10,000 rpm 3.5 in stroke drag engines are over 5500 avg. P/S, but they don't run long between rebuilds.

The F1 engine though sees almost double the stress and double the cycles per unit time because of the rpm. The G loading is not related to piston speed as much as rpm. Double the rpm at the same piston speed is double the forces at twice the frequency so it is more like 4 times as much wear!

The F1 engine though sees almost double the stress and double the cycles per unit time because of the rpm. The G loading is not related to piston speed as much as rpm. Double the rpm at the same piston speed is double the forces at twice the frequency so it is more like 4 times as much wear!

Yep, doubling the rpm (Cup > F1) doubles the piston gs, but interestingly enough the practice, qualifying and race lengths are about the same number of total engine revs in both series! With F1 having half the piston mass (or less) of a Cup engine, twice the gs, about the same piston speed, and approximately the same number of revolutions in anger, wear, or load cycles or whatever should be fairly close. Remember load is proportional to gs and mass, and stress is load per area (lb/sq. inch).

I think lots of endurance engine builders think in terms of number of cycles (revs). I'm pretty sure the metal does. :)

I don't think that F1 pistons are that light. They weigh around 275 g as far as what I have seen but the pins are still up there, but the rods are certainly lighter as short as they are which is good. Maybe we can get someone on here thatknows more of what a current one weighs? They have to be aluminum now as far as I know now too. The Cup stuff has to weigh a certain amount now but I don't know what it is? You are right that the races are only half as long though. You can't make something that's only ten percent less bore weigh 50 per cent less with the same materials and have it see twice the loading usually and live. I'd say the F1 piston with two rings weighs 75 percent the weight of the NASCAR piston maybe. I will try to find out since I really don't know right now.

One thing way different though is the shock and jerk loads the F1 rotating assembly sees when shifting and accelerating over bumps etc. The NASCAR engine stays in the same gear almost constantly whereas the F1 engine sees thousands of shifts. Some tracks are all out hell on the engine and gearbox.

I don't think that F1 pistons are that light. They weigh around 275 g as far as what I have seen but the pins are still up there, but the rods are certainly lighter as short as they are which is good. Maybe we can get someone on here thatknows more of what a current one weighs? They have to be aluminum now as far as I know now too. The Cup stuff has to weigh a certain amount now but I don't know what it is? You are right that the races are only half as long though. You can't make something that's only ten percent less bore weigh 50 per cent less with the same materials and have it see twice the loading usually and live. I'd say the F1 piston with two rings weighs 75 percent the weight of the NASCAR piston maybe. I will try to find out since I really don't know right now.

Actually they don't have a rule that states that the piston has to be aluminum. They just changed the rules to get rid of Beryllium in the parts because the dust produced by machining it is very toxic. The combination of Beryllium with Aluminum produces a very light yet extremely strong piston. The rules change just basically took Beryllium out of the equation but the parts are still very strong and very light. It makes no sense to see pistons with that much mass to them, at the RPM that F1 motors turn and the piston G's that reach 10,000 or more ever 5g's of mass is about 110 lbs of force on the rod/crank. That means that a 275g piston by itself would place 4/5ths of the total force that a Cup car sees on the rotating portion of the motor. (A Cup motor places about 8000 lbs of F on the crank and big end of the rod)That doesn't count the pin, the rings and the small end of the rod which adds another 30% to the mix or another 1800 lbs of F. With the metalurgy and technology that F1 engineers have I doubt that the modern F1 motors produced by Honda, BMW, Ferrari and Renault have pistons much over 200g's. The physics just don't warrant a piston with a mass that big.

A Cup motor has a 470g piston and pin mass and a 525g rod mass rule. They are restricted to a set mass and use aluminum pistons, Ti pins and steel rods. F1 doesn't have those limitations so they probably have much better mass to strength ratios for their base materials that allow them to place that many more G's on the parts. Considering that the piston G's double going to the F1 motor I would say they more than likely take advantage of better materials.

Bret

Bret,

I have some different F1 pistons and they are up to 300g with two rings. I think they are now aluminum only. Nextel primarily uses steel pins not Ti but F1 uses Ti rods. The F1 pins I have seen were also steel too although they have used all sorts of things.

The fact is that piston speed is not a good indicator of overall longevity compared to rpm. Otherwise an F1 engine costing much much more would be able to easily go 500 miles as well which it cannot even though it's average pistons speed is about the same. The valvetrain more than the shortblock is what's close to going on the Nextel engine too.

Bret,

I have some different F1 pistons and they are up to 300g with two rings. I think they are now aluminum only. Nextel primarily uses steel pins not Ti but F1 uses Ti rods. The F1 pins I have seen were also steel too although they have used all sorts of things.

The fact is that piston speed is not a good indicator of overall longevity compared to rpm. Otherwise an F1 engine costing much much more would be able to easily go 500 miles as well which it cannot even though it's average pistons speed is about the same. The valvetrain more than the shortblock is what's close to going on the Nextel engine too.

It's very surprising to me that you have access to modern F1 pistons. Almost no one outside of the users has that opportunity. How many valve reliefs? I'm dying to know the valve layouts.

When Be-Al alloys were outlawed, with a strength to mass ratio about 3-3.8 times that of plain aluminum (non-Be) alloy, the materials guys cooked up other alloys and MMC (metal matrix composites) which were legal and the same strength/mass. Everything I've ever read, and folks I've talked to at PRI have indicated F1 pistons are not just Aluminum alloys, but are very exotic.

Of course we differ on what determines modern race engine longevity, but that's ok. Agreeing to disagree makes a good discussion. :)

As I mentioned before, a Cup engine turns about the same number of revs in anger in a 500 mile race weekend (except for Plate races) as an F1 engine does in a typical race weekend. I believe F1 is going to a two-race engine rule for 2005. When they went from qualifying engines and race engines to the one-engine rule, power really didn't drop...just lap times.

No quarrel that valvetrain in Cup engines is iffy, but recent engine failures seemed to be internal/shortblock, but that could very well be from a dropped valve. Obviously the engine guys aren't telling us or each other. AFAIK, with current technology and extensive Spintron testing, Cup valvetrains are able to live at revs approaching 10,000. That puts the piston speed up over 5400 fpm, which I still think they can't yet survive. Isn't Cup going to a gear rule to limit rpm and "cut costs"? I haven't heard what that rpm limit will be. 9500 would be my first guess.

Didn't NASCAR recently outlaw some metals in the valvetrain?

My $.02

I am always amused by the rule changes in racing to "cut costs". They always seem to have the opposite effect. The only "cheap" racing, even at the amatuer level is a "spec" class. Like Sports 2000 in SCCA racing or even the IRL. But that eliminates the technical interest of most other race classes. I used to race Formula Ford. It was concieved as an inexpensive open wheel racing class by the SCCA. The rules were very restrictive but it was far from cheap. If you didn't have the latest chassis or the hottest new engine, you could forget winning at the National level. If I were to go road racing again, it would be in a "spec" class. Drag racing gets around this with brackets and such. Not a bad idea, but not going as fast as you possibly can somehow seems unilke "racing" to me.

Rich

It's very surprising to me that you have access to modern F1 pistons. Almost no one outside of the users has that opportunity. How many valve reliefs? I'm dying to know the valve layouts.

When Be-Al alloys were outlawed, with a strength to mass ratio about 3-3.8 times that of plain aluminum (non-Be) alloy, the materials guys cooked up other alloys and MMC (metal matrix composites) which were legal and the same strength/mass. Everything I've ever read, and folks I've talked to at PRI have indicated F1 pistons are not just Aluminum alloys, but are very exotic.

Of course we differ on what determines modern race engine longevity, but that's ok. Agreeing to disagree makes a good discussion. :)

As I mentioned before, a Cup engine turns about the same number of revs in anger in a 500 mile race weekend (except for Plate races) as an F1 engine does in a typical race weekend. I believe F1 is going to a two-race engine rule for 2005. When they went from qualifying engines and race engines to the one-engine rule, power really didn't drop...just lap times.

No quarrel that valvetrain in Cup engines is iffy, but recent engine failures seemed to be internal/shortblock, but that could very well be from a dropped valve. Obviously the engine guys aren't telling us or each other. AFAIK, with current technology and extensive Spintron testing, Cup valvetrains are able to live at revs approaching 10,000. That puts the piston speed up over 5400 fpm, which I still think they can't yet survive. Isn't Cup going to a gear rule to limit rpm and "cut costs"? I haven't heard what that rpm limit will be. 9500 would be my first guess.

Didn't NASCAR recently outlaw some metals in the valvetrain?

My $.02

I only am saying that piston speed is not a good indictor of overall longevity or stress as long stroke engines can operate at high pistons speeds in total endurance applications much better or by far than short stroke combinations can. These short stroke engines have good specific power but are extremely short lived as compared to their longer stroke counterparts.

I think now that MMC is also illegal in F1 as is the berylium stuff of any kind. The pistons are all two years old or older but they are all 4 valve reliefs since almost all are 4 valve engines and have been for some time. I know people that work in three F1 manufacturers. They are very trick but mostly just good engineering since they have outlawed so much of the special materials.

At one time they had some crazy pistons in F1 though! I will be at PRI like usual so maybe I can meet you guys there too.

I only am saying that piston speed is not a good indictor of overall longevity or stress as long stroke engines can operate at high pistons speeds in total endurance applications much better or by far than short stroke combinations can. These short stroke engines have good specific power but are extremely short lived as compared to their longer stroke counterparts.

I think now that MMC is also illegal in F1 as is the berylium stuff of any kind. The pistons are all two years old or older but they are all 4 valve reliefs since almost all are 4 valve engines and have been for some time. I know people that work in three F1 manufacturers. They are very trick but mostly just good engineering since they have outlawed so much of the special materials.

At one time they had some crazy pistons in F1 though! I will be at PRI like usual so maybe I can meet you guys there too.

Now I'm confused. Are you saying that longer stroke as opposed to shorter stroke is better for power and longevity for endurance (over a million revs) race engines? Why would you choose high piston speed (long stroke) instead of low piston speed (short stroke) for a given rpm? Haven't the high end engines like Cup, Pro Stock and F1 been increasing bore size and shortening strokes for the last 10 years or so, and thereby increasing rpm so that each lb-ft of extra torque produced near the max rpm is more hp? Please explain.

As for F1 materials, I think you are mistaken. Maybe IRL and CART (or whatever it's called now), but not F1. The 2004 F1 Technical specs specify steel or cast iron for the crank and camshafts, and prohibit composite materials using carbon or aramid fiber for pistons, cylinder heads or blocks. MMC doesn't seem to be prohibited.

Engines can have 5 valves. Strange that they don't.

Now I'm confused. Are you saying that longer stroke as opposed to shorter stroke is better for power and longevity for endurance (over a million revs) race engines? Why would you choose high piston speed (long stroke) instead of low piston speed (short stroke) for a given rpm? Haven't the high end engines like Cup, Pro Stock and F1 been increasing bore size and shortening strokes for the last 10 years or so, and thereby increasing rpm so that each lb-ft of extra torque produced near the max rpm is more hp? Please explain.

As for F1 materials, I think you are mistaken. Maybe IRL and CART (or whatever it's called now), but not F1. The 2004 F1 Technical specs specify steel or cast iron for the crank and camshafts, and prohibit composite materials using carbon or aramid fiber for pistons, cylinder heads or blocks. MMC doesn't seem to be prohibited.

Engines can have 5 valves. Strange that they don't.

The stroke/bore thing confused me too :confused: I thought F1 engines are 5V.

Rich

Bret,

I have some different F1 pistons and they are up to 300g with two rings. I think they are now aluminum only. Nextel primarily uses steel pins not Ti but F1 uses Ti rods. The F1 pins I have seen were also steel too although they have used all sorts of things.

The fact is that piston speed is not a good indicator of overall longevity compared to rpm. Otherwise an F1 engine costing much much more would be able to easily go 500 miles as well which it cannot even though it's average pistons speed is about the same. The valvetrain more than the shortblock is what's close to going on the Nextel engine too.

Seems to me that a strong 70g pin would be Ti and DLC surface treated.

How is it that a Cup motor can go 10K+rpm but we never see those speeds on the track? They have the valvetrain to do it, but they don't run 400-500 mile races with engine speeds that fast.

I still don't think that BMW, Ferrari and Honda are running pistons in the 300g range. If we can get 308g 4.030" bore 1.250" CH Aluminum off the shelf piston then someone is not taking advantage of all the material and design resorces out there. With a bore that is .145 smaller (3.888"), a compression height probably a good .250 (1.000")or more shorter that's a lot of mass out of a piston. So by just taking those dimensions with the piston specs above that's a 230g piston if it was aluminum, now use a material that is 3 times stronger and you can take even more mass out of it.

Something doesn't add up there.

As I said before ever 5g's is 110 lbs of F at 19,500rpm. A mass savings of 45g's is 1,000 lbs of F of of the pin, rod and crankshaft.

Bret

It's very surprising to me that you have access to modern F1 pistons. Almost no one outside of the users has that opportunity.

Erik has at least one friend who works for a company here in Detroit that has a sister company in England that designs F1 engines. The last F1 piston I saw, and still have, was from an early 90's Lambo V12. I got the piston/rod assy at Silverstone shortly after the engine was not used anymore.

Just think, for a paltry sum of money you could have bought Cosworth Racing in England just a few weeks ago.

Erik has at least one friend who works for a company here in Detroit that has a sister company in England that designs F1 engines. The last F1 piston I saw, and still have, was from an early 90's Lambo V12. I got the piston/rod assy at Silverstone shortly after the engine was not used anymore.

Just think, for a paltry sum of money you could have bought Cosworth Racing in England just a few weeks ago.

Early 90's they were just over 11,500rpm and the Lambo wasn't even a competitive motor.

Bret

Now I'm confused. Are you saying that longer stroke as opposed to shorter stroke is better for power and longevity for endurance (over a million revs) race engines? Why would you choose high piston speed (long stroke) instead of low piston speed (short stroke) for a given rpm? Haven't the high end engines like Cup, Pro Stock and F1 been increasing bore size and shortening strokes for the last 10 years or so, and thereby increasing rpm so that each lb-ft of extra torque produced near the max rpm is more hp? Please explain.

As for F1 materials, I think you are mistaken. Maybe IRL and CART (or whatever it's called now), but not F1. The 2004 F1 Technical specs specify steel or cast iron for the crank and camshafts, and prohibit composite materials using carbon or aramid fiber for pistons, cylinder heads or blocks. MMC doesn't seem to be prohibited.

Engines can have 5 valves. Strange that they don't.

Yeah that is the max number of valves but no one uses 5 anymore and hasn't for a long time as far as I know. MMC is usually fiber reinforced but I don't know if all MMC falls under the F1 rule? The pistons speed is limited by the airflow in the heads not the stroke or rpm. The longer stroke stuff just knocks the rpm way down. When you want specific hp you run shorter strokes so you try to get your inches in bore mostly to a point. This is NOT a reliability move ever. It's done to run more valve area VS CID. The valve area makes the power not the short stroke at all.

Seems to me that a strong 70g pin would be Ti and DLC surface treated.

How is it that a Cup motor can go 10K+rpm but we never see those speeds on the track? They have the valvetrain to do it, but they don't run 400-500 mile races with engine speeds that fast.

I still don't think that BMW, Ferrari and Honda are running pistons in the 300g range. If we can get 308g 4.030" bore 1.250" CH Aluminum off the shelf piston then someone is not taking advantage of all the material and design resorces out there. With a bore that is .145 smaller (3.888"), a compression height probably a good .250 (1.000")or more shorter that's a lot of mass out of a piston. So by just taking those dimensions with the piston specs above that's a 230g piston if it was aluminum, now use a material that is 3 times stronger and you can take even more mass out of it.

Something doesn't add up there.

As I said before ever 5g's is 110 lbs of F at 19,500rpm. A mass savings of 45g's is 1,000 lbs of F of of the pin, rod and crankshaft.

Bret

Bret,

Cup motors can't breathe well at 10,000 rpm due to the fact that they have one 4150.

Cup uses Steel pins usually in .866 size and F1 is usually Steel in the .750 range I think and it is for longevity. Qualifying motors used Ti pins sometimes.

F1 pistons did weigh less when they had the unlimited materials at their disposal.

I said they were "up to 300g" not at or over on the biggest bore stuff. The ones I have just seen weighed around 270g or so. Some are possibly lighter than that but not 200g as far as I know. I will try to find out how light an aluminum piston can be made for that usage! They have skirts that are hardly an inch by and inch on the sides so they are very very short.

Nothing american has a 308 g piston that makes any power and turns 19,000 rpm and 900+ hp. Stuff like that if for limited 2bbl motors that don't turn any rpm or don't have to last long. You can figure the desity vs min thicknesses and see that 200g even probably won't do it at that bore size even with inboard pins.

My point was and is that piston speed is not as good an indicator of lifespan at all as RPM is. 24 hour enduro motors have 4 inch strokes all over the place when the rules allow it. The rpm is way lower on these deals so they last a lot longer requardless of piston speed which is limited by induction and not parts anyway.

Early 90's they were just over 11,500rpm and the Lambo wasn't even a competitive motor.

Bret

Jeez Bret, it was just a cool souvenir. I couldn't exactly buy a Renault piston of the time and this was cheap. Now I'm all depressed. :(

Yeah that is the max number of valves but no one uses 5 anymore and hasn't for a long time as far as I know. MMC is usually fiber reinforced but I don't know if all MMC falls under the F1 rule? The pistons speed is limited by the airflow in the heads not the stroke or rpm. The longer stroke stuff just knocks the rpm way down. When you want specific hp you run shorter strokes so you try to get your inches in bore mostly to a point. This is NOT a reliability move ever. It's done to run more valve area VS CID. The valve area makes the power not the short stroke at all.

A few quotes:

"Metal Matrix Composite (MMC) material developed for Formula One piston .The aluminium and ceramic alloy in question offers a weight saving approaching that of aluminium-beryllium, together with excellent thermal characteristics. Unlike aluminium-beryllium, it has a lot of potential for inlet valve as well as piston manufacture, promising significant gains over titanium valves."


"The latest development of the (2004 Honda) RA004E V10 is believed to develop a staggering 960 HP, making it the most powerful engine in Formula 1. It uses advanced metal matrix composite (MMC) components to increase revs and consequently horsepower."

As long as the MMC doesn't use Carbon or Aramid fiber it appears to be legal. Ceramics have come a long way.

Four valves per cylinder is what I found for current F1 engines also. Perhaps 3D cams need the valves in line?

24 hour endurance engines are very different beasts from 500 mile Cup or 200 mile F1 engines. A 7000 rpm or so LeMans engine runs about 10 times as many revs as an F1 or Cup engine. A 10K Pro Stock engine turns over about 1000 revs in anger before it receives some attention.

"Different strokes for different folks" applies here. :)

Bret,

Cup motors can't breathe well at 10,000 rpm due to the fact that they have one 4150.

480hp 358 cube iron non ported heads with 2bbl carbs can't breathe or make power over about 6500rpm but I know they spin to 8,000rpm. Considering that the motors make almost 7-8hg of vacuum at that point they can't breathe up there either but you still run them that high.

A ristrictor plate motor increased in RPM when they gave them bigger holes in the plate, mostly because they have a higher HP peak RPM now, that's a constant relationship there. More cfm thru TB or Carb will allow the same motor to make HP at a higher RPM if it's not limited in other places.

The 750 based 4150 that they use is a limit, that's a given but the Craftsman Truck motors are limited to a 390 based 4150 and they still turn 9,000+rpm.

So if it's not induction limited (which it's not) valvetrain limited (which it's not) and gear rule limited (which it's not yet) friction limited (which it's not) what keeps the engine speeds to where they are now in Cup racing? Why do they have bore size limits on the motors? Why do they have minimum mass requirements on the pistons/pins and rods? Do ya think that is all connected someplace?

F1 pistons did weigh less when they had the unlimited materials at their disposal.

They still do have unlimited alloys at their disposal, they just can't use Be in them anymore.

I said they were "up to 300g" not at or over on the biggest bore stuff. The ones I have just seen weighed around 270g or so. Some are possibly lighter than that but not 200g as far as I know. I will try to find out how light an aluminum piston can be made for that usage! They have skirts that are hardly an inch by and inch on the sides so they are very very short.

It's just common sense and basic physics that says you can't do that and make it last 900km or 500miles.

Nothing american has a 308 g piston that makes any power and turns 19,000 rpm and 900+ hp. Stuff like that if for limited 2bbl motors that don't turn any rpm or don't have to last long. You can figure the desity vs min thicknesses and see that 200g even probably won't do it at that bore size even with inboard pins.

Never said anything ran 19,000rpm and made 900hp that used those pistons. I know they move about 4600-4800 ft per sec and can hold 600hp. They are just a example of mass of a given Al piston at a given size.

Given material with better strength to mass than Al it can certainly have a lower mass and be much stronger.

Why don't you read what Old SStroker says for a change and absorb it. He's told you time and time again that MMC's are not fibre based or don't have to be. I guess actually having that piece of paper that qualifies you as a ME is needed to understand that.

My point was and is that piston speed is not as good an indicator of lifespan at all as RPM is. 24 hour enduro motors have 4 inch strokes all over the place when the rules allow it. The rpm is way lower on these deals so they last a lot longer requardless of piston speed which is limited by induction and not parts anyway.

The correlation here is that piston speed and piston G's are the issue the byproduct of that is RPM and stroke, that's what gets you to engine longevity. The lower the piston speed and G's the less the parts are loaded and the longer they last.

4 inch strokes are in these motors because they have inlet restrictors that limit the RPM of the motors, that's obvious. It's also probably part of the rules that they have to have a production based block and displacement isin't limited. The C5-R is a great example of that. You can't get the same cubes out of these motors without new blocks and packaging concerns. A short deck height is one thing but wider bore spacing will produce much longer blocks.

Answer this then........

How about if the rules allowed you to run a Cup motor with better heads that worked on a smaller bore yeilding the same cfm that they get now on a 4.185" bore are you going to run a longer stroke so it will last longer?

It's a long day and it's going to be even longer.....

Bret

480hp 358 cube iron non ported heads with 2bbl carbs can't breathe or make power over about 6500rpm but I know they spin to 8,000rpm. Considering that the motors make almost 7-8hg of vacuum at that point they can't breathe up there either but you still run them that high.

A ristrictor plate motor increased in RPM when they gave them bigger holes in the plate, mostly because they have a higher HP peak RPM now, that's a constant relationship there. More cfm thru TB or Carb will allow the same motor to make HP at a higher RPM if it's not limited in other places.

The 750 based 4150 that they use is a limit, that's a given but the Craftsman Truck motors are limited to a 390 based 4150 and they still turn 9,000+rpm.

So if it's not induction limited (which it's not) valvetrain limited (which it's not) and gear rule limited (which it's not yet) friction limited (which it's not) what keeps the engine speeds to where they are now in Cup racing? Why do they have bore size limits on the motors? Why do they have minimum mass requirements on the pistons/pins and rods? Do ya think that is all connected someplace?


Bret,

They are limited by the combination of all of those things like all engines are including F1. Valvetrain is the limit and that is what they spend a lot of time on along with friction reduction and cylinder seal etc. As these elements have gotten better especially valvetrain and heads the motors turn more rpm now. The minimum mass requirements are for money.

How much do you think a NASCAR spec 390 flows? It's not really a 390 to give you a clue. It flows much more.

I don't understand much of the other stuff you have written?

They still do have unlimited alloys at their disposal, they just can't use Be in them anymore.


It's just common sense and basic physics that says you can't do that and make it last 900km or 500miles.


Never said anything ran 19,000rpm and made 900hp that used those pistons. I know they move about 4600-4800 ft per sec and can hold 600hp. They are just a example of mass of a given Al piston at a given size.

Given material with better strength to mass than Al it can certainly have a lower mass and be much stronger.

Why don't you read what Old SStroker says for a change and absorb it. He's told you time and time again that MMC's are not fibre based or don't have to be. I guess actually having that piece of paper that qualifies you as a ME is needed to understand that.

Unlimited means that you can run anything Bret, so they are no longer unlimited as I said. They used to use different MMC stuff in F! that WAS outlawed but apparently there is still "other" MMC in use that is currently legal. If you actually read what I said I noted that I did not know if "all" MMC fell under the F1 ban. I don't follow this stuff much anymore but still hear about it a lot.

It's all red herrings anyway as what the argument was really on was not the bobweight of a current cost no object F1 engine was but rather that piston speed is NOT a great indicator of wear and tear on an engine. Your dad also posted a combination of max and mean piston speeds that would only happen if the rods were shorter than the stroke. Anyway the point is that at the same pistons speed I can have DRAMATICALLY less wear and tear with DOUBLE the stroke since now I turn HALF the rpm at that SAME piston speed thereby cutting the "G" loads on half as your dad already agreed they would be cut.

What part are you arguing?

The correlation here is that piston speed and piston G's are the issue the byproduct of that is RPM and stroke, that's what gets you to engine longevity. The lower the piston speed and G's the less the parts are loaded and the longer they last.

Bret,

Piston speed does not directly correlate to piston "G"s as I just said. You can have double the piston speed without any additional force on the pistons and pins or you could have double the "G"s on one engine's pistons even though another engine had the same exact piston speed. You have to know the rpm and the stroke and the rpm component is much much more important.

High rpm KILLS parts. Piston speed does not.

What you are doing is making a TON of unseen assumptions that are not always true.

4 inch strokes are in these motors because they have inlet restrictors that limit the RPM of the motors, that's obvious. It's also probably part of the rules that they have to have a production based block and displacement isin't limited. The C5-R is a great example of that. You can't get the same cubes out of these motors without new blocks and packaging concerns. A short deck height is one thing but wider bore spacing will produce much longer blocks.

Answer this then........

How about if the rules allowed you to run a Cup motor with better heads that worked on a smaller bore yeilding the same cfm that they get now on a 4.185" bore are you going to run a longer stroke so it will last longer?

It's a long day and it's going to be even longer.....

Bret

Bret,

These are good conversations but I can't do it in one long post!

They run big strokes in these endurance engines to increase efficiency and they do just that. They can run short stroke smaller stuff but you will lose power in friction and lack of compression and surface to volume ratios etc. BSFC will get worse with the shorter strokes and get better with the longer ones. You will only get so much air by the restrictor so it's what you do with tha air that matters and the bigger engines with longer strokes make more power out of the same air.

On the cup motor it would be close but they run the big bore to get more air in and run larger more unshrouded intake valves. The short stroke reduces power but is necesarry to get back to the max engine displacement. If you are limited in airflow often they WILL run smaller bores for more efficiency since they can't get more air into the engine they just try to make the most out of what they have ala Kaase and WJ's "debored" Engine Masters winners.

Short stroke is a by product of fixed displacement and using a bigger bore to allow better breathing heads so you can make more power by keeping your tq up as high in rpm as possible. This comes from good breathing and the power it creates not just rpm on it's own. They could tame the cams ramps WAY down and run smaller valves and less lift etc. and even turn MORE rpm but they would lose power so no one does that.

It's all red herrings anyway as what the argument was really on was not the bobweight of a current cost no object F1 engine was but rather that piston speed is NOT a great indicator of wear and tear on an engine. Your dad also posted a combination of max and mean piston speeds that would only happen if the rods were shorter than the stroke. Anyway the point is that at the same pistons speed I can have DRAMATICALLY less wear and tear with DOUBLE the stroke since now I turn HALF the rpm at that SAME piston speed thereby cutting the "G" loads on half as your dad already agreed they would be cut.



Sorry to double team you, Eric. Once again, thanks for pointing out my typo on the BMW P83 engine. It was 40 m/s max, 25 m/s avg. I edited that post so it wouldn't confuse folks..

Approximately 75% of an engine's friction comes from piston/rings sliding on the bore, and is proportional to piston speed. That info comes from basic internal combustion engine text books like those written by Taylor and Taylor. My conclusion is that higher piston friction generally generates more heat and results in more wear.

If one limits mean piston speed to a given value, the shorter stroke produces higher rpm at that value, as we all seem to agree on. If indicated torque output per cubic inch is fairly constant for a given class of engines, like Cup, for instance, obviously making that torque at a higher rpm gives more indicated power. However, if friction hp (which is subtracted from indicated hp to get brake or flywheel hp) goes up due to more piston speed due to the long vs. short rod, then the net resulting brake hp will be less for the higher piston speed engine at the same rpm.

As you said, piston gs are proportional to rpm, especially if you keep the rod/stroke ratio equal. However, the resulting forces on the piston, rod and crank are proportional to the mass of the parts and the gs. If one can build lower mass parts sufficiently strong, and shorten the stroke to control piston speed, one can get more specific power than going the other way. IMO, which is never humble, that's where we've been heading for a long time in racing engines.

Sorry to double team you, Eric. Once again, thanks for pointing out my typo on the BMW P83 engine. It was 40 m/s max, 25 m/s avg. I edited that post so it wouldn't confuse folks..

Approximately 75% of an engine's friction comes from piston/rings sliding on the bore, and is proportional to piston speed. That info comes from basic internal combustion engine text books like those written by Taylor and Taylor. My conclusion is that higher piston friction generally generates more heat and results in more wear.

If one limits mean piston speed to a given value, the shorter stroke produces higher rpm at that value, as we all seem to agree on. If indicated torque output per cubic inch is fairly constant for a given class of engines, like Cup, for instance, obviously making that torque at a higher rpm gives more indicated power. However, if friction hp (which is subtracted from indicated hp to get brake or flywheel hp) goes up due to more piston speed due to the long vs. short rod, then the net resulting brake hp will be less for the higher piston speed engine at the same rpm.

As you said, piston gs are proportional to rpm, especially if you keep the rod/stroke ratio equal. However, the resulting forces on the piston, rod and crank are proportional to the mass of the parts and the gs. If one can build lower mass parts sufficiently strong, and shorten the stroke to control piston speed, one can get more specific power than going the other way. IMO, which is never humble, that's where we've been heading for a long time in racing engines.

Yep, I think that is "mostly" true but depends on the ring package! However think if they allowed you to run the same stuff at a longer stroke AND the same bigger bore then the rpm would drop down and you would make even more power but you'd of course have too many inches then!

I agree that sometimes you have less friction with the same inches at the same rpm with less stroke and more bore but believe it or not, people smarter than me at places say this is not always so also? In fact many classes DO run smaller bore stuff when they don't need the air the bigger bore stuff make possible. The ring "perimeter area" of drag grows at Pi times the diameter and the additional surface area of top of the piston increases the loading on the pin and rod journals too now.

This is exactly what WJ and Jon Kaase were also doing in their engine masters engines which had much more stroke and less bore than even stock engines. They obviously were NOT afraid of losing any power to friction when the stroked the hell out of these engines and shortened the rods up and the debored them. Most of the top small blocks this year were under 4.000 inch bore as well as Kaases again and Kuntzs and I think Bischoffs?

The ring "perimeter area" of drag grows at Pi times the diameter and the additional surface area of top of the piston increases the loading on the pin and rod journals too now.


Keep in mind also that for a ring to seal it needs unit pressure. That's generally how ring designs are rated when we compare engines of different bores and their ring sealing efficiency.

Thus, if you increase the bore diameter, and have to keep the ring's unit pressure the same to seal against the bore, your friction goes up right with it. As Erik says, if you don't need the bore diameter to allow more air in, this may not get you more power.

They are limited by the combination of all of those things like all engines are including F1. Valvetrain is the limit and that is what they spend a lot of time on along with friction reduction and cylinder seal etc. As these elements have gotten better especially valvetrain and heads the motors turn more rpm now. The minimum mass requirements are for money.

How much do you think a NASCAR spec 390 flows? It's not really a 390 to give you a clue. It flows much more.

I don't understand much of the other stuff you have written?

This just gets longer and longer doesn't it...

"So if it's not induction limited (which it's not) valvetrain limited (which it's not) and gear rule limited (which it's not yet) friction limited (which it's not) what keeps the engine speeds to where they are now in Cup racing? Why do they have bore size limits on the motors? Why do they have minimum mass requirements on the pistons/pins and rods? Do ya think that is all connected someplace?"

A Cup spec 4150 carb is not going to supply the motor with all the cfm it needs obviously, they probably see around 2" of Hg at HP or more with that carb on there. With another 400cfm they would find 30-40hp for those motors. Still it's not a RPM limit for the motors it's a restriction to the production of HP.

A 390 Truck Carb flows a bit more than that obviously, but like a Cup 750 based 4150 it still has a limit to how much it can flow.

The valvetrain systems have been tested to 10,000rpm or more, they survive and work up that high. Advances like spintron testing, lighter Ti valves (till they put a weight rule in for that) and better spring material allowed them to get the results they are looking for.

The friction is not an issue that limits RPM either. Small main and rod journals, roller cam bearings (for both spring load and friction), low drag seals, dry sumps and low drag rings all might add up to maybe 100-140 friction HP @ 9000rpm. Still not more than what the motor is making nor enough to limit the HP peak of the motor.

In 2002 they instituted the bore limits on the motors since the Mopar block allowed those teams to run much larger bores than the Chevy and Ford guys. I don't think this was just because they wanted to limit the airflow of the P7 heads, they did it because guy like Penske were turning 9000-9500rpm at places like Pocono. When Ryan Newman goes around that track without shifting and is going fast as or faster than the rest of the guys that motor is REALLY turning some RPM.

The minimum mass requirements are for money, but it's not the lighter weight steel rods that are what costs more I'm sure the rods cost the same price or more than they did now and not because steel is more expensive. RPM costs money plain and simple. The teams that still have that money spend it. (I.E. Hendrick) It's the same thing as a port that has the same volume and CFM as another head but makes more HP, a connecting rod with the same length and mass as another rod might not be as strong as another rod. You still spend the money making better parts, going to better grades of steel, spending money on better design of the parts etc..... just so the heavier rods can stay together at higher RPM. If they really wanted to save money they would put in a gear rule to keep RPM down, and low and behold they did.

RPM costs money everywhere and that's what the want to limit. NASCAR did things over time to try and limit RPM, first the bore limits, then the minimum masses of the parts, and finally they are saying it's enough, you only can turn the motor this fast because you are now going to run out of track to turn it any higher. Gear rules are the only way to limit RPM until the power increases enough to make the motor turn faster, then they just back off on the gears.

Unlimited means that you can run anything Bret, so they are no longer unlimited as I said. They used to use different MMC stuff in F! that WAS outlawed but apparently there is still "other" MMC in use that is currently legal. If you actually read what I said I noted that I did not know if "all" MMC fell under the F1 ban. I don't follow this stuff much anymore but still hear about it a lot.

It's all red herrings anyway as what the argument was really on was not the bob weight of a current cost no object F1 engine was but rather that piston speed is NOT a great indicator of wear and tear on an engine. Your dad also posted a combination of max and mean piston speeds that would only happen if the rods were shorter than the stroke. Anyway the point is that at the same pistons speed I can have DRAMATICALLY less wear and tear with DOUBLE the stroke since now I turn HALF the rpm at that SAME piston speed thereby cutting the "G" loads on half as your dad already agreed they would be cut.

What part are you arguing?

The part that was banned was the Be content, so now you know.

My point was that the parts just aren't going to live given known masses and piston speeds and accelerations with pistons that have 275-300g mass with that many piston speeds.

As for what the old man wrote....

FWIW, using the 19200 peak rpm, 40 m/s peak piston speed and 25 m/s avg. piston speed on a 10 cylinder engine of just shy of 3000 cc, I got the following:

Stroke:
39.065 mm (1.538 in.)

Bore: 98.75 mm (3.888 in.)

Displacement: 2992 cc

Rod length: 98.0 mm (3.858 in. )

R/S ratio: 2.51:1

And what you said about it...

Your dad also posted a combination of max and mean piston speeds that would only happen if the rods were shorter than the stroke.

Those numbers all relate. The rod is not shorter than the stroke, and the speeds are directly from Mario Thiessen engine development director of BMW F1 as stated in Racecar Engineering. They make sense too since the looks of the F1 motors 5.8-6" deck height is would be right.

Piston speed does not directly correlate to piston G's as I just said. You can have double the piston speed without any additional force on the pistons and pins or you could have double the G's on one engine's pistons even though another engine had the same exact piston speed. You have to know the rpm and the stroke and the rpm component is much more important.

High rpm KILLS parts. Piston speed does not.

What you are doing is making a TON of unseen assumptions that are not always true.

Actually I'm not making any assumptions here.

The lower the piston speed and G's the less the parts are loaded and the longer they last.

That's a fact. I never said piston speed wasn't linked to the stroke and RPM.

Piston speeds of F1 motors and Cup Motors are almost identical. Around 5000 ft/min.

19,200 RPM, 1.538" Stroke = around 5,000 ft/min (ex 4922 ft/min)
9,500 RPM, 3.25" Stroke = around 5,000 ft/min (ex 5146 ft/min)

Seems to be about the same limit don't ya think?

Now the G's on the pistons are much higher around (9,500-10,000 for F1, 5000-5300 on a Cup motor) that’s due to the higher RPM, makes sense to both of us obviously. My point is that the Force on the parts is relative to all of this. If the F1 parts can take more g's than the Cup parts but they have the same piston speeds then the motors are probably working with around the same max F at max RPM. That's where the whole piston weight thing comes from, I figured you would have worked that out but I guess not.

So actually it's not the RPM that "KILLS the parts" as you say it's the Force acting on them that does. So you basically proved my point. The issue is why they break, it's not RPM alone that does it. RPM and piston speed give you the G's, the mass of the parts with the G's give you the Force and that's what makes the car go BOOM!

They run big strokes in these endurance engines to increase efficiency and they do just that. They can run short stroke smaller stuff but you will lose power in friction and lack of compression and surface to volume ratios etc. BSFC will get worse with the shorter strokes and get better with the longer ones.

The problem here is that I talk about the motor in terms of a set cube limit, not the same bore longer or shorter stroke. If you have the same swept volume and same chamber volume you get the same compression ratio.

In the same instance you are stating

They can run short stroke smaller stuff but you will lose power in friction

Like a 406 vs. a 377 the 377 doesn't have more friction HP, it has less friction HP per RPM. It's pretty much a set ratio.

As for the BSFC there is more of a relationship in with the compression or lack there of than there is with the stroke. Given the 377 and 406 with the same compression ratio, they would be very similar given that we don't have stupid domes and decent chambers in each motor. Now if you look at say a Busch motor vs. a Cup motor that drop in compression from 12:1 to 9.5:1 shows a loss in BSFC efficiency. If you can't compress the air/fuel charge as much so it makes much less power per pound of fuel consumed.

Continued.............

You will only get so much air by the restrictor so it's what you do with that air that matters and the bigger engines with longer strokes make more power out of the same air.

Yeah but I think this is more of a combination of things than just XXX amount of air and XXX amount of cubes.

If given XXX amount of air from a restrictor it seems obvious that you need more cubes to make more power with the given amount. Problem is that more cubes with said restriction will lower the RPM the motor turns and produce about the same amount of HP. A smaller motor with the said restrictor will turn more RPM but the loss of TQ probably can't be made up by the extra gear given to the motor, but then again Super Stock racing is a good example of what can happen here.

The endurance motors don't want RPM for the whole piston speed, piston G's and force reasons we have talked about, they want TQ and a useable RPM band for the drivers to use for 6,12,24 hours at a time.

My thought is that stroking a motor to gain cubes is done when bores can't be enlarged any more. If you can use a bigger bore to get the same cubes then you do that as we see in tons of racing situations where there is a set cube limit (F1, Cup, NHRA Pro Stock) When you don't have cube limits or the cube sizes you need to run are huge for the block you are using then you add stroke to gain the cubes (IHRA Pro Stock and Sprint Cars) More on that down the page when I get to the Engine Masters stuff.

On the cup motor it would be close but they run the big bore to get more air in and run larger more unshrouded intake valves. The short stroke reduces power but is necessary to get back to the max engine displacement. If you are limited in airflow often they WILL run smaller bores for more efficiency since they can't get more air into the engine they just try to make the most out of what they have ala Kaase and WJ's "debored" Engine Masters winners.

Again, we are talking about a set amount of CUBES per set amount of CUBES. Without changing the displacement of the motor. The short stroke reduces power BECAUSE it is a reduction in displacement, not because it's a shorter stroke. Take that same Cup motor with a 4.128" bore / 3.25" stroke and change it to a 4.040" bore / 3.48" stroke, same 358 cubes. Which one will make more power and last longer with the same mass parts?

Short stroke is a by product of fixed displacement and using a bigger bore to allow better breathing heads so you can make more power by keeping your tq up as high in rpm as possible. This comes from good breathing and the power it creates not just rpm on its own. They could tame the cams ramps WAY down and run smaller valves and less lift etc. and even turn MORE rpm but they would lose power so no one does that.

So you agree that the 4.185" bore / 3.25" stroke is going to make more power.

Power output is the goal here not just RPM. Taming the lobes would produce less lobe area reducing output for a given duration cam, same thing with reducing lift (even though you could run a shorter spring and valve and same valvetrain mass) and less valve are would just reduce airflow and that's never going to help HP.

I agree that sometimes you have less friction with the same inches at the same rpm with less stroke and more bore but believe it or not, people smarter than me at places say this is not always so also?.....

The ring "perimeter area" of drag grows at Pi times the diameter...

That's a interesting thought (no not that you actually think that there are people are smarter than you lol)

The less surface area that the ring puts on the bore is obviously an issue here. Looking at the 4.185" and 4.040" examples with a .043"/.043"/3.0mm Ring set. We have to account for the expander in that ring set so let’s say that gives you .130" of vertical on that ring stack, which translates into 1.788 sq in of ring surface area with a 4.185" bore, and 1.666 sq in of ring surface area on the 4.040" bore. That's a 7% increase in ring surface area, which should relate to 7% more drag but...... Then you need to account for the piston speed and the distance it has to travel (stroke) to figure out how much drag you actually have here. The smaller bore has less ring surface area (7% less), but a longer distance to travel (7% longer distance) and it has to do it much faster (7% faster) given the same RPM. Now I would say that for a given piston speed the smaller bore motor will have less friction HP, but for a given RPM which is the real limit we have here the motor will have more piston speed and therefore more friction. It's going to be very hard to test these things and we are talking about very small differences in HP output if everything else was the same, but you can't do that since the drastic change in bore size would obviously hinder the cylinder heads in the case of cup motors or your average motor. There are some cases were it is not a problem..... again down the page.


..... and the additional surface area of top of the piston increases the loading on the pin and rod journals too now.

The pin loading might increase, that depends on the piston design. The rod loading in compression is still going to be a given for the pressure in the cylinder which is related to HP level. That's another long story that we can talk about later.

In fact many classes DO run smaller bore stuff when they don't need the air the bigger bore stuff make possible......

This is exactly what WJ and Jon Kaase were also doing in their engine masters engines which had much more stroke and less bore than even stock engines. They obviously were NOT afraid of losing any power to friction when the stroked the hell out of these engines and shortened the rods up and the debored them. Most of the top small blocks this year were under 4.000 inch bore as well as Kaases again and Kuntzs and I think Bischoffs?

I luckily got to go this year and watch the EM as the only spectator that was not an employee of Bill Mitchell, or of Primedia or a sponsor or contestant. WJ wasn't there but Sonny was and I did get to talk with Kaase about his motor.

Kaase's bore was 3.970" with a 4.125" stroke and a 6" rod, a lot like last year, just with a smaller bore. Now sitting down and talking to the man was very interesting, and I did get to learn some thing but at the same time I knew some of his answers were more of a redirection than an answer. Asking the right questions and getting a real answer was the key here.

In his situation or any guy who is in a position to like that of a guy working on a Cup team in the engine department or a Pro Stock team you have to look at what they actually tell you and wonder if it's "declassified".

A good example I can give is one of OldSStrokers flying buddies from the Air Force was a test pilot in the 70's into the 90's. He flew things that he can't even tell his wife about, and just until a few years ago he couldn't even say that he crashed one of the test planes in the Have Blue program (Stealth Fighter) and that was in the mid 70's! We have no idea what things he flew, and what we do know is 25 years old. Racing is a lot like that but it's not as long of a timeframe. I'm sure the things that people can tell us are not what happened yesterday, but some of the things are just depends on how important they are and if it's not a new or recent thing.

Going back to talking with Kaase and then reflecting on the design and answers gets you someplace. The first thing I asked him when he mentioned the bore size of 3.970" was if the heads flowed at that bore size. He said they flowed really well on a 4.00" bore so it wasn't an issue. The way he welded up the chambers, which in turn moved the valves closer together and farther away from the bore walls (because it's a canted valve Cleveland) is obviously going to make the bore size less important. The next question is obviously why the longer stroke? His simple answer was that the longer arm is better for TQ. Again he answers what he wants and doesn't answer what he doesn't want.

The one thing you have to remember with Jon is that his business is building motors with very large strokes relative to other racing motors out there. The bore/stroke ratio of his 408 cube Cleveland was REALLY close if not the same to his 815 cube Mountain Motors, and his 468 cube SCJ BBF was really close to the same bore/stroke of his 698 cube Sportsman motors. Honestly I think he's sticking with what he knows. He understands motors that work with those combinations, and in that challenge development time is at a premium. Just look at his site to see how many ported Cleveland intakes he has for same in the overstock section. No doubt his combos work , but that's not the whole story.

Also one little known fact out there is that Jon has been beat in the Engine Masters arena. Norm Grimes in 2003 built a big bore short stroke BBC and actually put down more average with the legal contest mufflers than Jon did, he just screwed up and ran the race mufflers that were not allowed. The funny thing is that the race motors made less power, so he would have not been DQ'ed and would have one with the legal mufflers.

It's been real and it's been fun but has it been real fun?

Bret

Keep in mind also that for a ring to seal it needs unit pressure. That's generally how ring designs are rated when we compare engines of different bores and their ring sealing efficiency.

Thus, if you increase the bore diameter, and have to keep the ring's unit pressure the same to seal against the bore, your friction goes up right with it. As Erik says, if you don't need the bore diameter to allow more air in, this may not get you more power.

Good point. Of course if you want to keep displacement and max rpm the same, the displacement is increasing at the second power of the bore diameter, but directly with stroke/piston speed. The motoring power curves I've seen are not linear; they increase slope a little with piston speed.

For sure one would have to balance friction hp increases against brake hp increases when increasing bore size/ring drag, stroke/piston speed, and rpm/gs/part mass. Obviously OEM designs also have many more parameters involved.

It will be interesting to see what direction Cup engines go if NASCAR implements a "gear rule" which is really a "max rpm rule". My guess is that if it's around 9500, we won't see longer strokes.

IF Cup "plate" engines have the same bore/stroke sizes as unrestricted engines, mean p/s is closer to 4100 than 5100 fpm for plate engines due to the 1800 or so less rpm. That's a lot less ring friction, so my guess is that the b/s dims are about the same to keep the p/s as low as possible. These guys will sell their mothers for a couple of brake hp on a plate engine, and friction is a good place to find it. I'll bet the "plate" engines have the smallest journals and bearings possible.

I wonder about rotating inertia on plate engines, because at speed they don't vary much (a few hundred rpm) during a lap. If inertia is high, could that help when they have to llift a little to avoid bumping? With a momentary lift, might not high inertia keep the "momentum" up? Anyone have any knowledge of this?

Bret,

Nascar Cup motors are limited by the valvetrain. Some of us know this and some of us obviously don't. They don't make more power or power any higher because of this and they also have airflow limitations of the single 4150 carb. This is not hard to understand. Friction also rises with rpm and some of it's components are exponential and some are more linear but none get BETTER with rpm.

Your dad said that the F1 engine had a max piston speed of 45 m/s and then an average of 25 m/s. He edited it then later after I said that couldn't be possible. You must have already forgetten in one day? I'm sure it was just a misprint as I said and I was right.

You can't say that STROKE is hurting or helping anything unless you hold everything else CONSTANT like bore etc. What you are doing is changing multiple things at once and then saying the longer stroke is bad. This is not true and it is known not to be true. When holding CID constant you can make more power with a BIGGER BORE generally because of increased valve area NOT because of the shorter stroke. Shorter strokes on their own REDUCE power and efficiency.

You also can NOT say that because you are spinning more rpm at the same pistons speed that the forces will be equal when they are DOUBLE. You are plain wrong. You can't assume that you can't run just as light a parts in the long stroke engine because you CAN. Also high rpm engines as per your example HAVE TO HAVE parts with 1/2 the weight if they turn double the rpm. This shows again how wrong it is to use piston speed as a stress indicator!

You can't make statements about his stuff if you are changing multiple variables at a time.

Bret,

It's not anyone's opinion that you have more pin loading and compressive loading with a bigger bore and the same inches! If you make 1000 psi cylinder pressure at TDC on both then the bigger bore motor has exactly it's bore difference SQUARED more force going down on the piston top. This is simple stuff. MORE bore area mulitiplied by the same cylinder PSI equals MORE force. That's the way that works. The shorter stroke knocks the force the cranks sees right back down though since it has less leverage on it now. The rod though sees more compressive stress plain and simple with a bigger bore.

Jon Kaase builds all sorts of motors as does WJ and so do the other guys and they did the exact opposite of what you say must be done to make good power and they won as did most of even the first sets of engine builders. Ask some of these guys why they didn't all build 4.200 bore and 3.700 stroke motors? Maybe they just don't know as much about engines as you do?

IF Cup "plate" engines have the same bore/stroke sizes as unrestricted engines, mean p/s is closer to 4100 than 5100 fpm for plate engines due to the 1800 or so less rpm. That's a lot less ring friction, so my guess is that the b/s dims are about the same to keep the p/s as low as possible. These guys will sell their mothers for a couple of brake hp on a plate engine, and friction is a good place to find it. I'll bet the "plate" engines have the smallest journals and bearings possible.

Have you ever seen the cup cranks for sale all over the place? They are known to come in two distintive stroke ranges? I wonder why this is?

They change stuff all the time. It all depends on the rules and budgets. People thought that you could have too much exhaust only a while back with those things etc.

Usually when trying to make all out power though you run as big a bore as possible when the rules are unlimited to allow the largest possible intake valves and with a set displacement limit that also means a shorter stroke. It doesn't get any more simple than that.

This is a dead horse already.... When are we going to get a smiley with a hammer on here beating a dead horse?

I'm sick of writing the same thing time and time again because you don't take the time to read it fully the first time. I give you that respect and it's just something I think people should reciprocate.

NASCAR Cup motors are limited by the valve train. Some of us know this and some of us obviously don't.

Good point..... I had a good talk today about this exact topic with someone who actually knows how fast they can go and what they can do, I think you would be surprised what the answer is. Then again it's a dead horse, I'm not going to change your mind and actually I don't really have any interest in it.

They don't make more power or power any higher because of this and they also have airflow limitations of the single 4150 carb. This is not hard to understand. Friction also rises with rpm and some of it's components are exponential and some are more linear but none get BETTER with rpm.

Said all that already. 2" of Hg vacuum etc..... Friction etc....

Your dad said that the F1 engine had a max piston speed of 45 m/s and then an average of 25 m/s. He edited it then later after I said that couldn't be possible. You must have already forgetten in one day?

Dead horse point again. It was a mistake, he fixed it. Hey I don't get on you for not changing the oil on Rick's motor when the turbo went so give up already. WE ALL MAKE MISTAKES, I do, he does and so do you And anyways it would be much more manly of you to say that to him (but not 3 times like you have) and not bring my family into this, this is one of those times it's better to be on the net rather than sitting next to each other in a bar. Personal = Not Cool, Professional = Proper. As I said Dead Horse, you look like an ass brining it up again and again. I might be stepping out of line with this statement but I'm not one of those people who will let his values be stepped on, period.

I'm sure it was just a misprint as I said and I was right.

Basically what this thread seems to be about anymore. You being right. Good luck with that.

Now back to the topic at hand..........

You can't say that STROKE is hurting or helping anything unless you hold everything else CONSTANT like bore etc. What you are doing is changing multiple things at once and then saying the longer stroke is bad. This is not true and it is known not to be true. When holding CID constant you can make more power with a BIGGER BORE generally because of increased valve area NOT because of the shorter stroke. Shorter strokes on their own REDUCE power and efficiency........

......You can't make statements about his stuff if you are changing multiple variables at a time.

Actually I've said you have to hold it constant and change one thing this entire thread. Just because you brought it up here doesn't mean you invented this idea. Go back, reread the posts (for the first time) and you'll notice that I mentioned stroke length changes using the same displacement numerous times.

OTOH, the thought of changing a bore and not seeing what goes with that is dumb. If there is an increase in airflow with an increase in bore size that needs to go with it. It's the chain of events that needs to be recognized and added into what is changing the situation. Your examples of changing the stroke only in a motor don't isolate what we are looking at, similar cubes and compression are factors that have to be isolated when you are talking about things that change the power curve less drastically.

You might want to think about the "shorter strokes on their own REDUCE efficiency" thought. Is the reduction in mechanical drag, reducing efficiency?


You also can NOT say that because you are spinning more rpm at the same pistons speed that the forces will be equal when they are DOUBLE. You are plain wrong.

Forces don't = G's, G's are part of the equation for F (i.e. F=MA)

That's the point. The forces should be equal, BECAUSE the mass should be cut in half every time the piston G's double. Therefore the force is the same. The force is the key here and it's what states the limit of the motors RPM, the piston speed just shows you what the physical limits of the materials at hand in the different racing classes.


Continued.............

You can't assume that you can't run just as light a parts in the long stroke engine because you CAN.

Actually that was my point with this..........

Again, we are talking about a set amount of CUBES per set amount of CUBES. Without changing the displacement of the motor. The short stroke reduces power BECAUSE it is a reduction in displacement, not because it's a shorter stroke. Take that same Cup motor with a 4.185" bore / 3.25" stroke and change it to a 4.040" bore / 3.48" stroke, same 358 cubes. Which one will make more power and last longer with the same mass parts?

I was assuming the same mass (not weight, different things W=M x g) for the parts since the example was a Cup motor with a set mass for all the parts in the motor. Actually you could run lighter parts in the long stroke motor, unless you change the deck height.

Also high rpm engines as per your example HAVE TO HAVE parts with 1/2 the weight if they turn double the rpm. This shows again how wrong it is to use piston speed as a stress indicator!

Actually, if you are going to say that you have to get it right. It's that they turn double the RPM with the same max piston speed. Therefore the piston G's with be double, therefore for the F to be constant the mass has to be 1/2.

Everything is linked together. I'm not saying x is what counts it's a bunch of things added together.

RPM and piston speed give you the G's, the mass of the parts with the G's give you the Force and that's what makes the car go BOOM!

BTW again with the mass = weight thing, I made my point about the company namesake before. Engineers don't screw those two up.

You can't cheat physics. Try running a motor with the same mass at twice the G's for the same length of time. How is that going to turn out? They only have to have the same requirements for durability, if you throw that out the window you can cheat the numbers at bit more but in time Mother Nature will bite you in the ass.

It's not anyone's opinion that you have more pin loading and compressive loading with a bigger bore and the same inches! If you make 1000 psi cylinder pressure at TDC on both then the bigger bore motor has exactly it's bore difference SQUARED more force going down on the piston top. This is simple stuff. MORE bore area multiplied by the same cylinder PSI equals MORE force. That's the way that works. The shorter stroke knocks the force the cranks sees right back down though since it has less leverage on it now. The rod though sees more compressive stress plain and simple with a bigger bore.

I made a mistake (actually another value you might want to pick up, humility it comes with self image)

PSI x Surface Area = Pounds of Compressive Force pushing on the parts.

Again this is another long topic that maybe we can talk about when you are not picking on a guys family.

Jon Kaase builds all sorts of motors as does WJ and so do the other guys and they did the exact opposite of what you say must be done to make good power and they won as did most of even the first sets of engine builders. Ask some of these guys why they didn't all build 4.200 bore and 3.700 stroke motors? Maybe they just don't know as much about engines as you do?

Jon does build other motors, getting outside of Drag Racing for him as he said "is more for fun to see what I can do than anything" I was lucky enough to have this talk with him face to face and get in the guys head to see why he did what he did. I also have a ton of respect for that guy and a bunch of the guys in that contest, he would be one guy that if you beat would be a great accomplishment.

Can you do me a favor and find WJ on this page for me? http://www.popularhotrodding.com/enginemasters/challenge/2004/results/

Guy has never touched an EM motor. Now there are rumors as to other guys doing it, but never once did I hear WJ or KJ mentioned.

Also one little known fact out there is that Jon has been beat in the Engine Masters arena. Norm Grimes in 2003 built a big bore short stroke BBC and actually put down more average with the legal contest mufflers than Jon did, he just screwed up and ran the race mufflers that were not allowed. The funny thing is that the race motors made less power, so he would have not been DQ'ed and would have one with the legal mufflers.

Eric, I really think that saying that the jury is out on the best combination for an Engine Masters motor is Kaase's way is very narrow minded. Knowing the real story as to what is going on here will say a lot. I've been there, talked to the people and got the story that they can't print. How can they say that Grimes made a score of 1182 to 1178 for Kaase but got kicked out because one place said his mufflers were street mufflers and one place said they were not. That just takes away from Jon's accomplishments and actual win which he deserved. It doesn't prove the point that small bore big stroke is the best way to go. In fact the #4 guy did a bunch with the opposite setup with much less knowledge, money and technology than Kaase, Tony and the Williams boys had. I think a lot of what is going on now is that since Jon did the small bore big stroke in the Big Blocks guys want to follow the leader because he won. Sad fact is nobody is going to beat that guy if they keep doing the same thing as him, he's just going to be much better at it than they are. It's like Greg Anderson, they're not going to beat him coping him they can only beat him if they think outside the box and fix whatever he is doing wrong, which apparently is not much.


Hey I'm done with this thread. It's beating on a dead horse back and fourth, and personally it's wasting time for me. Its good reading material for everyone else but it's just pointless if the guy on the other end is waiting to talk so he doesn't read what you write. I can see that in your writing and when it happens to me with a person in real life I cut the conversation short, as I'm doing now. We can continue this in another thread in some other time.

Bret

Lots of good stuff posted here, especially by Bret and Jon, but also others. But the discussion got very complicated. I think is because of the number of variables introduced by the various contrbutors to the thread. The following scenarios are very different when it comes to engine design. Modifying an existing production based block for max hp produces a vastly different combo than a purpose built race motor. Displacement limits, $$$ available, rpm limits, intake area limts, etc. all will change the equation. But most of the people here are interested in modifying production blocks for max performance. In that situation, the answers are clear: first bore it as much as practical and then stroke it as much as practical. Displacement rules and that is why you NEVER see a competitive engine that has anything less than the max cubes allowable or feasible. The only exception is the circumstance where someone can throw enough cubic money at the problem to trump cubic inches. But all else being equal, cubes rule.

Rich

72* ATDC huh?


FWIW: friction is a HUGE deal to F1. HUGE. If you dont think it is, think again.

from my limited understanding, its a big part of the reason why the theory of best layout bounces from V10 to V12. but I only get to pick at the race guys brains, I dont have them so I'll leave it at that.

doesn't friction increases to a power of 2 with respect to velocity? I know air drag is anyway.

Bret,

No one is making fun of your family. You and your dad often double team people on here like you two have all the answers. Your dad even mentioned it in jest but most of the CamaroZ28 crowd here was suprised since many didn't know that you two were related until recently. I know it makes a lot more sense to most of us after knowing that, as obviously you have a common mind set which is not to say your always wrong.

The problem is that people get their physics wrong as in the piston speed being a prime stress indicator when it is not. Another one you just mentioned being that you doubted that short stroke engines in general are less efficient than longer stroke engines. What is the average bracket 632 CID BSFC numbers and what is a mega dollar <300 CID Comp engine that makes over 2.7 hp/inch? I think you routinely interchange the word efficiency for hp/inch which are NOT the same and any engineer would know that or should. Unless we are on different planets weight and mass are almost interchangeable but they are different so I agree that mass is the right word (even though we are obviously in the same frame of reference).

I don't usually see your dad, OldSStroker saying that type of stuff but rather you and then you defend it with strange "science" that no one understands?

I say that big engines are usually more efficient and more powerful and that is true with all else equal.

I say that longer stroke engines also are usually more efficient and powerful which is also true all else equal.

I say that bigger bore engines make more power due to bigger intake valves which is also true all else equal.

I say that shorter strokes usually decrease power and efficiency which is also true all else equal.

I said that when MMC(some fiber based) was banned earlier in F1 that they went right back to aluminum and that the pistons weighed from 275g to 300g which is also true since I know several people in F1 and several piston companies that do F1 pistons or did back then. I know that earlier some even weighed 320g and that was in the 90s and was on a V12 of even smaller bore size.

I said that I didn't know if MMC of all types were banned which was true and your dad, OldSStroker, pointed out correctly that they are now using many "other" MMCs that are legal and I totally believe him that he is right even though I haven't checked yet.

Lastly I am not in the least perurbed or angry at all but it certainly seems that you are? I would say that you need to sit back and just breath and think a bit about what you are saying. Tell me if anything I said above is wrong because I see you saying that and so do others and these are things commonly seen, documented and agreed on.

Lots of good stuff posted here, especially by Bret and Jon, but also others. But the discussion got very complicated. I think is because of the number of variables introduced by the various contrbutors to the thread. The following scenarios are very different when it comes to engine design. Modifying an existing production based block for max hp produces a vastly different combo than a purpose built race motor. Displacement limits, $$$ available, rpm limits, intake area limts, etc. all will change the equation. But most of the people here are interested in modifying production blocks for max performance. In that situation, the answers are clear: first bore it as much as practical and then stroke it as much as practical. Displacement rules and that is why you NEVER see a competitive engine that has anything less than the max cubes allowable or feasible. The only exception is the circumstance where someone can throw enough cubic money at the problem to trump cubic inches. But all else being equal, cubes rule.

Rich

Rich,

All you say is true except at the end because there will always be another Bill Gates spending the big paper on the BIG engine and he will take the other Bill Gates with the SMALL engine every time!

Dead horse point again. It was a mistake, he fixed it. Hey I don't get on you for not changing the oil on Rick's motor when the turbo went so give up already. WE ALL MAKE MISTAKES, I do, he does and so do you And anyways it would be much more manly of you to say that to him (but not 3 times like you have) and not bring my family into this, this is one of those times it's better to be on the net rather than sitting next to each other in a bar. Personal = Not Cool, Professional = Proper. As I said Dead Horse, you look like an ass brining it up again and again. I might be stepping out of line with this statement but I'm not one of those people who will let his values be stepped on, period.

Bret,

I don't change Rick's oil and I was not even there when this happened in the first place? These kinds of posts are just bizzare? None of this really matters that much so don't get so worked up about it. Hell Rick's doing stuff to go even faster and I'm sure he will. We need more people doing this stuff rather than talking about it anyway. We need to get together at PRI if you aren't still so mad because I am one jolly person in real life! I think Danno would love to meet you guys too if you are there.

Can someone fill me in on the drama?

Whos related.
who changes whos oil
whos rick?

Boost it,

It's stuff that is totally unrelated to anything being discussed. Rick has an LT1 car that went 8.30s at 168-170 the first time he went down the track and then the next morning at Thunder the turbo was destroyed during that night? It has nothing to do with your question or anything though at all. It will go much faster when it hits the track again after PRI probably 7s. It's all LT1 stuff so it is also a stock block.

I was sure someone sent you a spreadsheet of the formulas though for finding instantaneous and peak piston speed and piston acceleration and if not I can if you would like one. The ACCELERATION of the piston is the key to the stress not it's velocity or piston speed. The formula for FORCE is F=MA so if you know the mass of the parts being accelerated you can find the forces that muct be acting on them. The rpm you are at affects the acceleration (and thus forces) of the piston as a square where as piston speed from more stroke at the same rpm is a linear increase.

Then there's the fact that most engines peter out in rpm due to the heads and valvetrain which is what really sets the upper limit on piston speed and rpm in the first place not bottom end components. Of course these bottom end components must be strong enough to take the accelerations that the final engine build dishes out to them. It's very hard to do that AND lighten everything up a lot over what is already being used with the lower rpm stuff already. Another words I can get just as light a piston for a 410 chevy as a 310 chevy. We all know which one makes much more power.

Rich,

All you say is true except at the end because there will always be another Bill Gates spending the big paper on the BIG engine and he will take the other Bill Gates with the SMALL engine every time!

I agree. A good big one will beat a good little one every time!

Rich

Boost it,

It's stuff that is totally unrelated to anything being discussed. Rick has an LT1 car that went 8.30s at 168-170 the first time he went down the track and then the next morning at Thunder the turbo was destroyed during that night? It has nothing to do with your question or anything though at all. It will go much faster when it hits the track again after PRI probably 7s. It's all LT1 stuff so it is also a stock block.

I was sure someone sent you a spreadsheet of the formulas though for finding instantaneous and peak piston speed and piston acceleration and if not I can if you would like one. The ACCELERATION of the piston is the key to the stress not it's velocity or piston speed. The formula for FORCE is F=MA so if you know the mass of the parts being accelerated you can find the forces that muct be acting on them. The rpm you are at affects the acceleration (and thus forces) of the piston as a square where as piston speed from more stroke at the same rpm is a linear increase.

Then there's the fact that most engines peter out in rpm due to the heads and valvetrain which is what really sets the upper limit on piston speed and rpm in the first place not bottom end components. Of course these bottom end components must be strong enough to take the accelerations that the final engine build dishes out to them. It's very hard to do that AND lighten everything up a lot over what is already being used with the lower rpm stuff already. Another words I can get just as light a piston for a 410 chevy as a 310 chevy. We all know which one makes much more power.
please send:D

Boost it,

Will send it to you from home!

A good big one will beat a good little one every time!

Rich

That applies in other areas also. To quote an OLD line from my youth, "That's what she said."

;)

Damn guys..... felt like I just read a book. Feel like you just wrote one?

There always has been and always will be debates regarding engine design and what works best. The good point of all this is they keep getting better each year.

Thanks for all you're insights. You guys really should get together if you're all at a certain event. Probably enjoy it more than you realize.

That applies in other areas also. To quote an OLD line from my youth, "That's what she said."

;)



its from my youth...and in still in it :skep:

It's very surprising to me that you have access to modern F1 pistons. Almost no one outside of the users has that opportunity. How many valve reliefs? I'm dying to know the valve layouts.

When Be-Al alloys were outlawed, with a strength to mass ratio about 3-3.8 times that of plain aluminum (non-Be) alloy, the materials guys cooked up other alloys and MMC (metal matrix composites) which were legal and the same strength/mass. Everything I've ever read, and folks I've talked to at PRI have indicated F1 pistons are not just Aluminum alloys, but are very exotic.

Of course we differ on what determines modern race engine longevity, but that's ok. Agreeing to disagree makes a good discussion. :)

OldSStroker,

Well asking all my crazy sources I get 240-270G for Aluminum F1 pistons and 215-245g for Aluminum MMC pistons so far. They have lighter versions too as does everyone in real racing but they are not run in the actual race engines but rather like a test or an older qualifying engine or on the two teams that are 100 HP down like the AsiaTech. Still that is CRAZY light. I know who makes the pistons in MMC for most of the teams including BMW. All that I know of still only run 4 valves though. I've seen lots of the 5 valve stuff but I guess it doesn't make the power at this time.

The F1 engineers are MUCH more concerned about the bottom end life in terms of RPM though rather than piston speed asking two so far as they also noted that the old "stroker" F1 engines used in some popular endurance racers usually turn as high a piston speed while lasting even 12 and 24 hour races at the lower rpms and larger strokes that they run these engines at. Some of them also have made close to the same power even with restrictors in them but at larger sizes!

Speaking of all this crazy F1 stuff were you at PRI? Did you see any of the trick bearings speaking of friction reduction at 20,000 rpm?

OldSStroker,

Well asking all my crazy sources I get 240-270G for Aluminum F1 pistons and 215-245g for Aluminum MMC pistons so far. They have lighter versions too as does everyone in real racing but they are not run in the actual race engines but rather like a test or an older qualifying engine or on the two teams that are 100 HP down like the AsiaTech. Still that is CRAZY light. I know who makes the pistons in MMC for most of the teams including BMW. All that I know of still only run 4 valves though. I've seen lots of the 5 valve stuff but I guess it doesn't make the power at this time.

The F1 engineers are MUCH more concerned about the bottom end life in terms of RPM though rather than piston speed asking two so far as they also noted that the old "stroker" F1 engines used in some popular endurance racers usually turn as high a piston speed while lasting even 12 and 24 hour races at the lower rpms and larger strokes that they run these engines at. Some of them also have made close to the same power even with restrictors in them but at larger sizes!

Speaking of all this crazy F1 stuff were you at PRI? Did you see any of the trick bearings speaking of friction reduction at 20,000 rpm?

You also saw the AisaTech (1999) pistons/crank/rods also at PRI, I assume. 233 gms for one style of piston. Yeah, 4 valves and the valve reliefs are most of the combustion chambers. Mahle had some interesting stuff to say about F1 pistons, also. Unfortunately not much about current stuff. "We'd have to shoot you..." They suggested that today's F1 piston are NOT heavier than the '99 AsiaTech ones. :)

I believe ProStock has a piston weight rule if about 460 gms. That's about 100 gms more than pre-rule pistons according to some of the piston guys. 360 gms for a 4.6+inch bore pumping out 175+ hp/hole is pretty good. If piston weight is somewhat proportional to bore size ^2, and F1 engines have 3.8 to 3.9 bores, the math is interesting when you compare F1 and ProStock pistons.

Cosworth (Jag?) F1 engine was interesting also, as is the tech book on 2000 Ferrari F1. These had variable length inlet trumpets which cycled length as many as four times from 11000 to 18000 rev range.

I agree that piston speed isn't too much of a factor mainly because they (F1)are keeping it below 5000 fpm, which is lower than Cup. I doubt that they would increase it 15% if they were looking for 15% more rpm, however. I think we will see F1 engines continue to spin faster, and have larger bore/stroke ratios which are 2.3+ now in F1, but only 1.3 or so in Cup. With the Cup "gear rules" for 2005, we may not see much more rpm there.

Bearing speeds are very high on F1 engines compared to Cup. With rod journals around 1.45(F1) vs 1.85(Cup) and twice the revs that's got to be a challenge.

I believe ProStock has a piston weight rule if about 460 gms. That's about 100 gms more than pre-rule pistons according to some of the piston guys. 360 gms for a 4.6+inch bore pumping out 175+ hp/hole is pretty good. If piston weight is somewhat proportional to bore size ^2, and F1 engines have 3.8 to 3.9 bores, the math is interesting when you compare F1 and ProStock pistons.

.......

Bearing speeds are very high on F1 engines compared to Cup. With rod journals around 1.45(F1) vs 1.85(Cup) and twice the revs that's got to be a challenge.

I know many pro stockers and with the exception of maybe GA no one I know has ever seen PS pistons that light! I can find out but I know the aluminum berylium MMC stuff for PS was almost that light and that is now banned in PS too. Apparently the Berylium and fiber based MMCs were almost unbelievable though in lightness and overall strength.

Those F1 bearings cost over 35,000 dollars an engine!

Any theories why Anderson has been cleaning up in Pro Stock?

He has it all together. If anyone knew exactly why then they would be as fast too! I know the NASCAR connection there didn't hurt Greg. Those guys see stuff all the time that they can't use but that a drag racer could due to the endurance requirements that the NASCAR stuff must meet compared to Pro-Stock. He has a great team and the cars, engines and drivers are all doing a great job. Grumpy was doing good there too for a while. It also has a great deal to do with the teams resources and budgets. WJ has been running the DRCE3 so that is where he has been this year.

He has it all together. If anyone knew exactly why then they would be as fast too! I know the NASCAR connection there didn't hurt Greg. Those guys see stuff all the time that they can't use but that a drag racer could due to the endurance requirements that the NASCAR stuff must meet compared to Pro-Stock. He has a great team and the cars, engines and drivers are all doing a great job. Grumpy was doing good there too for a while. It also has a great deal to do with the teams resources and budgets. WJ has been running the DRCE3 so that is where he has been this year.

How about any specifics as to what Anderson is doing different mechanically from the others. Perhaps he's running a small bore, long stroke? ;)

I know many pro stockers and with the exception of maybe GA no one I know has ever seen PS pistons that light!

Funny I picked up 2 360g Pro Stock Pistons at the CP booth. 4.600" Bore, around 1.000" Compression Height, kind of thought they were PS pistons and CP reaffirmed that. They are old news now since they can't even run them that light anymore because of the rules.

Also confirmed that Al F1 pistons from the 16,500rpm AsiaTech motor were 230-236g's by two different compaines. Guessing is good but when you see the parts in person it's much better.

Oh and asking the right cam people how fast could I turn a 358 cube motor with a pushrod, rocker arm setup like oh say a Cup motor the response I got was "You could go 11,000 if you wanted too, I can make the valvetrain turn as fast as you want it too. More RPM is just going to cut down on the aggressiveness." I would say he probably knows a few more people working on valvetrains in Cup than anyone you know, so it's a pretty good source.

Interesting show indeed.

Bret

Funny I picked up 2 360g Pro Stock Pistons at the CP booth. 4.600" Bore, around 1.000" Compression Height, kind of thought they were PS pistons and CP reaffirmed that. They are old news now since they can't even run them that light anymore because of the rules.

Also confirmed that Al F1 pistons from the 16,500rpm AsiaTech motor were 230-236g's by two different compaines. Guessing is good but when you see the parts in person it's much better.

Oh and asking the right cam people how fast could I turn a 358 cube motor with a pushrod, rocker arm setup like oh say a Cup motor the response I got was "You could go 11,000 if you wanted too, I can make the valvetrain turn as fast as you want it too. More RPM is just going to cut down on the aggressiveness." I would say he probably knows a few more people working on valvetrains in Cup than anyone you know, so it's a pretty good source.

Interesting show indeed.

Bret

The Asiatech was the weakest thing out there in F1. It was for sale to anyone. With less power and RPM you can lighten anything up. You are not seeing anything that really runs in F1 at PRI. The Vendor that really sells more F1 pistons wasn't far away and it wasn't CP either. They just made those rods and you could see how big the bolts were! For such light parts and moderate piston speed. I wonder if RPM had anything to do with that instead?

Those super light CP pistons won't make any power in a PS motor either. Anyone can lighten up a piston by machining it down on the bottom to a very low thickness but that doesn't mean that is what they really run. CP has not sold any 360g pistons to anyone I know in PS including the ones that are winning and that's from the guys that really build them everyday Bret. They are much heavier. I don't even know of anyone running CP in PS in fact.

I already told you that they can turn more rpm and you could too by laming out the valvetrain but you will lose horsepower and airflow that way. When you are racing you are trying to MAKE, not LOSE horsepower. The piston speed and this RPM where they make power is due to their valvetrain and heads. A stock valvetrain can turn 11,000 with a stiff spring and a .200 lift cam. Does that mean anything really?

NO.

Bret, although I can not name names if you asked a lot about the F1 cranks they would have told you or you would have seen the bobweight numbers. Some run as heavy as a 290g piston even in 2003 if you know the balance and the other parts etc. The guy at Chambon with JE said he had seen even 300g lately on some other stuff in F1 and they are the ones that made that stuff on display at CP. Pankl made the rods on that engine but CP makes nothing else on that.

I was told that at least one good running BMW piston lately still weighed over 230G and was MMC so even though the stuff is light that is on display doesn not mean it will go the whole distance at a lot or power and rpm. I also heard that some other MMC pistons were as low as 200g on a smaller bore motor. I don't follow it as much as I should but I do know the guys that make those pistons very well but they will lose their job if they actually talk about anything current.

I absolutely agree that the MMC stuff is lighter and in the current form it is legal in F1! But the whole discussion that you are changing was whether piston speed was a good indicator of mechanical stress which limits race engines or whether as I said it was an airflow limitation that kills power at a certain piston speed and it IS airflow as far as why no one can usually get over a certain piston speed. To find mechanical stresses we use the variable in this form (RPM^2 X Stroke) and piston speed uses the same variables in this form (RPM X Stroke) so there is a very big difference between the two as RPM is MUCH more important to mechanical stress and cycle life than piston speed is.

The Asiatech was the weakest thing out there in F1. It was for sale to anyone. With less power and RPM you can lighten anything up. You are not seeing anything that really runs in F1 at PRI. The Vendor that really sells more F1 pistons wasn't far away and it wasn't CP either. They just made those rods and you could see how big the bolts were! For such light parts and moderate piston speed. I wonder if RPM had anything to do with that instead?

Those super light CP pistons won't make any power in a PS motor either. Anyone can lighten up a piston by machining it down on the bottom to a very low thickness but that doesn't mean that is what they really run. CP has not sold any 360g pistons to anyone I know in PS including the ones that are winning and that's from the guys that really build them everyday Bret. They are much heavier. I don't even know of anyone running CP in PS in fact.

I already told you that they can turn more rpm and you could too by laming out the valvetrain but you will lose horsepower and airflow that way. When you are racing you are trying to MAKE, not LOSE horsepower. The piston speed and this RPM where they make power is due to their valvetrain and heads. A stock valvetrain can turn 11,000 with a stiff spring and a .200 lift cam. Does that mean anything really?

NO.

Yeah, Yeah Mahle makes F1 pistons we know that. But then again you would remind me if I didn't dot my i's and cross my t's if this was hand written.
The Asiatech motor was weak and not even current but that's not the point. The piston mass was for that and other F1 motors. You still said that they were 275-300g's for a Al piston. Mahle stated that Al pistons were at the most 230gs in what they do now. They also said they used other alloys but it's not like they are going to say what they use. I don't blame them.

Go up the page and I think you will see you explicitly said that Cup motors were valvetrain limited. Now you are just stepping on your toes about it changing what you said about it. Your new postion just copies what I said in new language.

Both of those things you've taken a 180deg position on. For your posts to be that YOU are right all the time, don't you think you need to at least be right?

As for the PS piston...I just picked up the PS piston at CP and talked with them about it, maybe they don't run them in PS, but that's what it was made for. If they do or don't run them I don't know, but the only real way to know would be to be WJ, Grumpy or Anderson. The piston didn't have a super thin crown so it might have worked but they can't run them anyways so it makes sense that they show it since the new piston mass has to be 460g's now.

Bret

I absolutely agree that the MMC stuff is lighter and in the current form it is legal in F1! But the whole discussion that you are changing was whether piston speed was a good indicator of mechanical stress which limits race engines or whether as I said it was an airflow limitation that kills power at a certain piston speed and it IS airflow as far as why no one can usually get over a certain piston speed. To find mechanical stresses we use the variable in this form (RPM^2 X Stroke) and piston speed uses the same variables in this form (RPM X Stroke) so there is a very big difference between the two as RPM is MUCH more important to mechanical stress and cycle life than piston speed is.

Wouldn't that basically be piston g's?

When did you say before this that "an airflow limitation that kills power at a certain piston speed and it IS airflow as far as why no one can usually get over a certain piston speed. "

Yeah, Yeah Mahle makes F1 pistons we know that. But then again you would remind me if I didn't dot my i's and cross my t's if this was hand written.


I wasn't talking about Mahle.

Bret,

I said that I remembered MMCs being banned back then which they were temporarily. Now different MMCs are back. This thread was about finding piston velocity and then it was discussed that piston speed was synonomous to stress and it is not. I know people that make F1 pistons but have not talked with them in around 2 years but I knew at that time that everyone thought stuff was lighter than it really was and that is still the case.

Piston "Gs" are not directly tied to piston speed at all but rather another formula as they increase exponentially with RPM whereas piston speed does NOT. This is simple.

Also Bret the valvetrain LIMITS airflow when it starts causing false motion and airflow is no longer happening in the right direction so valvetrain limitations causes airflow limitations and power falls off.

WOW, I want to thank all you fellows for a lively interchange of ideas and information and I want to thank Damon in particular for his explanation of max piston velocity. His exercise with wire/t-square/protractor made me smile as it all came clear to me about the rod being 90* to the crank throw at 75* ATDC. Short of being a degreed engineer, that's the way I find myself understanding how things work, by laying them out and looking at them. I'm now further asssuming that the only way to get max piston velocity at 90* ATDC would be to offset the main journal a distance equal to the radius of the crank throw in relation to the bore centerline. I realize this wouldn't work well coming back from BDC to TDC, I'm just visualizing it to bring it all together in my mind. Although I've been building motors for myself and friends on a hobbyist level for over 40 years, it's just something I never thought much about.

I'm coming over to the camaroz28 site from another forum where I've become bored and stifled with the inane chatter served up there. There seems to be a very good collection of sharp minds here and I'm looking forward to learning from you fellows.

I'm 62, semi-retired and living with my wife of 34 years in Phoenix. I began tech inspecting in 1958 at a little airport runway/Sunday drag strip called Dahio just outside of Dayton, Ohio. I currently inspect at Firebird Int'l Raceway in Chandler, AZ where I've been since 1990 (that's the "semi-retired" part of it). :D

Nice to have you Richard and you are basically correct about offseting the rod a crazy amount like that (although then on the stroke back up you would have a really crazy rod angle!) or you could use an infinitely long rod and then you would basically be back to sinusoidal motion with the max piston speed at 90 degrees. That rod would be really heavy though!

Yeah Erik, it would have to be made of "unobtainium" :eek: