rskrause

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

Rich

SStrokerAce

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

94bird

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.

SStrokerAce

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

Bret

racer7088

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.

racer7088

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.

94bird

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.

OldSStroker

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.

SStrokerAce

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?

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.

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

racer7088

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?

racer7088

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?

racer7088

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.

racer7088

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.

OldSStroker

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.

racer7088

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?