Top fuel engines, im intrigued, bear with me

I guess the thread in LT1 about the 660rwhp NA LT1 kinda got me wondering.

How exactly do the top fuel (4 second cars) obtain the what, 6000hp they have I believe I read somewhere.

I read something in a mag I have somewhere that the engine sees a few gallons of fuel coming into it in a matter of a second or something.

If anyone knows, Im just really curious as to what kinda stuff goes on, heads, cams, blocks, CI, nitrous setups, FI setups. I mean it all just doesnt make sense how something can produce that much power.

Originally posted by jonaddis84
How exactly do the top fuel (4 second cars) obtain the what, 6000hp they have I believe I read somewhere.

I read something in a mag I have somewhere that the engine sees a few gallons of fuel coming into it in a matter of a second or something.

If anyone knows, Im just really curious as to what kinda stuff goes on, heads, cams, blocks, CI, nitrous setups, FI setups. I mean it all just doesnt make sense how something can produce that much power.

A lot of it is the fuel. Nitromethane contains lots of it's own oxygen. Here's a short writeup frm HowStuffWorks:

http://www.howstuffworks.com/question642.htm

There is also another reaction with nitro which isn't exactly combustion. It's more of a "cracking" reaction which releases more power. I don't fully understand it, however.

Here's a few more "facts" courtesy of www.dieselinnovations.com

* The 500-inch Hemi makes more horsepower than the first 8 rows at Daytona.
* Under full throttle, a the engine consumes 1 1/2 gallons of nitro per second, the same rate of fuel consumption as a fully loaded 747 but with 4 times the energy volume.
* The supercharger takes more power to drive then a stock hemi makes.
* Even with nearly 3000 CFM of air being rammed in by the supercharger on overdrive, the fuel mixture is compressed into nearly-solid form before ignition. Cylinders run on the verge of hydraulic lock.
* Dual electronic magnetos apply 44 amps to each spark plug. This is the output of an arc welder in each cylinder.
* At stoichiometric (exact) 1.7:1 air/fuel mixture (for nitro), the flame front of nitromethane measures 7050 degrees F.
* Nitro methane burns yellow. The spectacular white flame seen above the exhaust pipes at night is raw burning hydrogen, dissociated from atmospheric water vapor by the searing exhaust gases.
* Spark plug electrodes are totally consumed during a pass. After 1/2 way, the engine is dieseling from compression-plus the glow of exhaust valves at 1400 degrees F. The engine can only be shut down by cutting of its fuel flow.
* If spark momentarily fails early in the run, unburned nitro builds up in those cylinders and then explodes with a force that can blow cylinder heads off the block in pieces or blow the block in half.
* The engines twist the crank (torsionally) so far (20 degrees in the big end of the track) that sometimes cam lobes are ground offset from front to rear to re-phase the valve timing somewhere closer to synchronization with the pistons.
* To exceed 300mph in 4.5 seconds dragsters must accelerate at an average of over 4G's. But in reaching 250 mph well before 1/2 track, launch acceleration is closer to 8G's.
* Drivers must shut off before the finish line, or even dual parachutes will not stop the car.
* If all the equipment is paid off, the crew worked for free, and for once NOTHING BLOWS UP, each run costs $1000.00 per second. Bear in mind here that the engine behind all this Herculean output is a modified offshoot of a common American big-block V-8

The more nitro that can be crammed in, the more power they get. The engine is basically hydrolocked with the liquid nitro.

Note that burning occurs thruout the power stroke and most of the exhaust stroke. The excess fuel burned in the upturned headers give a significant amount of download onto the tires.

The engines turn about 8000 for 4.7 seconds or so, or less than 700 revs in anger before they are rebuilt.

Most of this is so bizzare that it's difficult to believe. So is 6000 hp from 500 cubes, IMO, but it happens.

It takes 2000 HP just to turn the blower.

Just a little factoid stuff...

Nitromethane is a military grade explosive.

A mixture of Nitromethane and, I believe, Aniline, is used in devices like the Mine Clearing Line Charge and hasty tank traps.

In the MCLC a hose attached to a rocket is filled with nitromethane based explosive and fired into a mine field where it's detonated and the overpressure sets off the mines.

In a hasty tank trap, you use a device similar in concept to a Ditch Witch, which lays underground sprinkler hose.

You bury the hose well underneath a road, and if you have to "blow the road", you pump the NM explosive into the hose and detonate it, which creates a large trench that both wheeled and tracked vehicles can't drive through.


Nitromethane can also be used as a sensitizer in an ANFO explosive (Ammonium Nitrate + Fuel Oil), to achieve a brisance (burn velocity) comparable to PETN and RDX. (the major ingredients in C-4 & Semtex)


So the amazing thing about Fuel Cars is not how much power they produce, but how they manage to keep the engine intact long enough to make a pass!




And no... I'm not going to teach any of you juvenile delinquents how to make explosives, so don't ask! :p :D :p

Nitromethane isn't much of a primary explosive unless you have a sensitizer in it though - but when you do it can definately work as such - aniline (as you mentioned), or really most organic amines will work as such - you just want something that is highly soluble so you get proper dispersion. But in the context it is used here I don't think you are going to get in a situation where it becomes a primary explosive (any hopefully you don't have any detonating caps stored with you fuel :))

Under full throttle, a the engine consumes 1 1/2 gallons of nitro per second, the same rate of fuel consumption as a fully loaded 747 but with 4 times the energy volume.

I have heard that before, but not 100% sure I buy it. (the 4* the energy volume part). But not sure what they actually mean by "energy volume". Say 60,000 lbs of thrust per engine, * 4 engines - your typical 747 is making 240,000 lbs of thrust. If we assume a speed of 330 knots that is 240,000HP. Now sure, that is power, not energy (not sure what energy/volume is) - but 240,000HP vs. 6,000HP.... don't know if I see that comparison happening. Evey if they are talking simply "cruising" for the 747 I think it takes ~60,000HP at 330knots.

Originally posted by Stephen 87 IROC
It takes 2000 HP just to turn the blower.

Well, maybe 400+hp.

You couldn't put 2000 hp through a 3 inch timing belt moving at 200+ ft/sec, especially when the engine/blower accelerate from 1800-2000 rpm idle to 8000(engine)/12000(blower) in a few tenths of a second.


Nitro can also be used as a rocket fuel, so maybe Top Fuel really is rocket science. :)

Anyone familiar with Hydrazine? A couple of guys tried some in fuel dragsters in the 60s. Mixed with nitro it makes the fuel more shock sensitive, as well as nasty to humans. Big booms though.

i went to the drags here in germany. i had all day pit passes i got a rod and piston that was still warm and a head from a top fueler i paid 60 bucks for it all. i was standing about 10 feet away from one of the dragsters while they were setting it up it took all i could do to stand 10 feet away at idle and my eyes started watering i felt like i was in a C.S chamber then he revved it one quik time and i thought my ears were going to pop i couldnt hear good for about 2 days. i have lots of pictures of thier engines and stuff they were pretty good about letting me get some closeups of thier setups and the thing about the spark plugs is true i have 2 of them autolite 50s i believe is what they are and yes the electrode is completly gone. and talking about fuel consumption my cousin owns (SNIPER) the monster truck (Robert French) from cali and his truck has 2500 and some change. he moved it from his moms house to 1/8 mile down the road and burnt 15 gallons of alcohol so i believe the fuel consumption on a top fueler

I was under the impression that the "energy volume" referred to the potential energy stored in that 1 1/2 gallons of fuel burned per second, ie. a gallon of nitromethane has 4X the potential energy as 1 gallon of jet fuel.

I'm just thinking they used the wrong terms, maybe they meant that the fuel car makes more power per pound of weight compared to a 747.

using 240,000 HP at 330 knots(I think the newer 747s make anywhere from 59,500 lbs or thrust to 63,300 lbs)

With a max take off weight of 875,000lbs to 910,000 lbs

thats about .27 HP/lb

for the fuel car at 6000 HP and minimum of 2100 lbs thats

2.86 HP/lb.

thats still way more then 4 times the power to weight ratio of the 747 but maybe thats what they are talking about? :confused:

I dunno you guys are the genius's ;)

P

What about gearing? I have always wanted to know what kind of gear ratio (transmission and rear) allows a car to be able to get off of the line hard and travel 330 mph. They are 1 speed right? I assume it does not take much gear to get off the line with 6000 HP on tap.

Wow. Thanks guys, this stuff is quite amazing, keep the replies coming Im sure others are quite interested as well.

BTW anybody know anything about the nitrous guys? Or are those that I am thinking only on the funny cars in the 6 second area?

Originally posted by Turbo6
I was under the impression that the "energy volume" referred to the potential energy stored in that 1 1/2 gallons of fuel burned per second, ie. a gallon of nitromethane has 4X the potential energy as 1 gallon of jet fuel.

Jet fuel is about 30-35 MJ/L, Nitromethane is only about 10MJ/L (both at STP)

You have to burn alot more nitromethane to make the same amount of power as an identical volume of jet fuel.



Anyone familiar with Hydrazine? A couple of guys tried some in fuel dragsters in the 60s. Mixed with nitro it makes the fuel more shock sensitive, as well as nasty to humans. Big booms though.

Now that's getting crazy :) Hydrazine is some really nasty stuff - you could run it through the catalytic converters on our car with a nozzle out the back and duplicate a basic jet engine (massive decomposition to ammonia, nitrogen, and hydrogen - then the hydrogen burns with air if you are really lucky)

Chris

Top fuel cars all run a mandatory 3:20 rear gear. A good friend of mine just bought Bruce Littons complete top fuel operation, he's going to run most of the NHRA season this year. I'll try to get some general info about cam specs, head flow#'s etc.

Originally posted by Chris B
Jet fuel is about 30-35 MJ/L, Nitromethane is only about 10MJ/L (both at STP)

You have to burn alot more nitromethane to make the same amount of power as an identical volume of jet fuel.



I'll take your word for that, but its worth mentioning that with a stoich AF ratio of 1.7:1 for nitro and jet fuel being much closer to diesel or gasoline, you can burn a lot more fuel per displacement of the engine. I don't know exactly what the original author meant by energy volume either though.

3.20 gear, some slippage, and big arse tires that expand and act like a centrifugal clutch of sorts.

-brent

Originally posted by dkeers
What about gearing? I have always wanted to know what kind of gear ratio (transmission and rear) allows a car to be able to get off of the line hard and travel 330 mph. They are 1 speed right? I assume it does not take much gear to get off the line with 6000 HP on tap.

TF and FC have gear rules. 3.20 is the gear as WickedFast said. Of course the tires grow a lot during the run so there is some variable ratio.

Yep, it's one speed forward. Additionally the clutch slips a lot! It is applied at a rate determined by mechanical timers: no computers allowed. You can see the carbon dust from the many plates pouring out of the bellhousing area. Too much clutch and they go up in smoke. Remember the engine goes to 8000 almost immediately and the car catches up. 6000 hp @ 8000 is about 4000 lb-ft torque. All of that is trying to wind up the rear axle housing. You can see the torque reaction in the chassis as the 300 in wheelbase TF chassis arches it's back nearly a foot!

At speed, the rear wing gives something like 6000+ lbs of downforce.

While acceleration near the line is better than 5 g, that's"eyeballs in". When the drag chutes come out it's that or more "eyeballs out". Detached retinas can be a major concern to the drivers.

TF cars run about 60% faster than a F1 or Cup car ever goes. There are about 43 people in the "300 MPH Club" at Bonneville Salt Flats. That's ever. In a typical weekend NHRA meet, there are more 300+ runs than thatjust in Top Fuel. Add Funny Car and the number doubles.

Flow numbers on those things would be interesting. A buddy of mine is crew chief on a match race fuel car, and I've looked over their heads. They're rectangle port, and absolutely giant.

What I've never understood is how the blocks last as long as they do. They have individual sleeves in an aluminum block, and to me it seems they should do all sorts of distortion, but I guess they don't, since they don't push head gaskets very often.

I doubt they even use head gaskets, its probably a o-ring type seal around the cylinder. i believe pro50 guys do this also.

Originally posted by OldSStroker

Anyone familiar with Hydrazine?

Anhydrous Hydrazine? :D

Originally posted by LameRandomName
Anhydrous Hydrazine? :D

What else?

C Stoff? 30% hydrazine hydrate + 57% methanol perhaps? :)

No, I wasn't referring to McVeigh, if that's where you are going?

A few guys blew up a few fuel rails by mixing hydrazine in with the nitro, doing a wheelie and dropping it hard back on the tarmac. Boom!

this is cool stuff to read :D :bow:

Im confused about all this hydrazine talk, Im assuming all you guys that know so much about it have studied it in an advanced chemistry class or something like that? And it sounded like one guy is in the military in demolition or something?

We did some testing on my friends alcohol Hemi and it takes ~200hp to drive the SC. It's similar in size and design to the ones used on TF cars, but is spun at ~60% the speed. Shouldn't it take ~2X the hp to drive the blower on a TF car then? I am not too good at math and physics, but that would imply ~400hp to drive the blower on a fuel car.

Rich Krause

Originally posted by JordonMusser
I doubt they even use head gaskets, its probably a o-ring type seal around the cylinder. i believe pro50 guys do this also.

Florocarbon {sp?} o-rings!
Moranmotorsports.com can do them:)

I love this topic, always interesting!

I don't know if it has been answered, but the top fuelers don't
use a gear box.

It's a direct couple from the crankshaft to the driveshaft via a massive clutch.

I have seen the head ports up close ... you can easily stick a closed fist down there!

One question I do have from an earlier post:

The engines turn about 8000 for 4.7 seconds or so, or less than 700 revs in anger before they are rebuilt.

"less than 700 revs before they are rebuilt"

Where does the 700 revs come into play?

Thanks for the clarification

Originally posted by Zero_to_69
I love this topic, always interesting!

I don't know if it has been answered, but the top fuelers don't
use a gear box.

It's a direct couple from the crankshaft to the driveshaft via a massive clutch.

How do they back them up after a burnout? maybe a gearbox with 1 forward and one reverse gear??

One question I do have from an earlier post:

The engines turn about 8000 for 4.7 seconds or so, or less than 700 revs in anger before they are rebuilt.

"less than 700 revs before they are rebuilt"

Where does the 700 revs come into play?

Thanks for the clarification

8000 rev/m / 60 sec/min = 133 revs/second x 4.7 seconds = 625 total revs at wide open throttle (in anger so to speak).

Of course that's only 313 firings per cylinder.

Rebuilding engines: pistons, rings, rods, and bearings are replaced after every run. Often more parts.

700 revs might be high. ;)

FWIW, a Nextel Cup engine makes maybe a million revs+ in anger in a typical Cup race. F1 not far behind, and gaining as they force them to use one engine longer.

Originally posted by rskrause
We did some testing on my friends alcohol Hemi and it takes ~200hp to drive the SC. It's similar in size and design to the ones used on TF cars, but is spun at ~60% the speed. Shouldn't it take ~2X the hp to drive the blower on a TF car then? I am not too good at math and physics, but that would imply ~400hp to drive the blower on a fuel car.

Rich Krause

Good info, Doc.

Wish I'd said that. ;)

Gotcha OldSS...

But the absence of a gearbox I'm referring to is a multi-speed
type. TF are only allowed 1:1 in forward ... that's what I meant
by direct couple.

Here is a photo of the clutch and transmission used.

http://w1.331.telia.com/~u33106502/dr/images_dr/koppling1.JPG

http://w1.331.telia.com/~u33106502/dr/images_dr/backv.jpg

BTW - Thanks for the explanation of 700 Revs! :)

Originally posted by Zero_to_69
Gotcha OldSS...



Using your siggy "One Million CID and Unlimited Nitromethane" and a little more math:

6000hp/500 CID = 12 hp/cube x 1,000,000 CID = 12 million hp.

If things like that scale up. Oh, yeah, that's on 90% nitro. :)

Uh oh...let me restate that:

Gotcha OldSS = Understood your explanation :bow:

Not

"Ha ha, you messed up"

Truth be told, besides the couple of photos I see and interviews
from Amato, Force, Skuza, etc. I know sweet f**k all about
top fuel/funny cars

PS: I like your math. 12 Million HP would do some damage with
traction huh?

Back to the thread!

what is their 60' times?
1/8 et and mph?

jesse

I "think" it's about 1.0 second for the 60 foot time.

0-100 MPH happens in about one second as well according to
"The Learning Channel" (< good source of info? :))

Originally posted by Zero_to_69
I "think" it's about 1.0 second for the 60 foot time.

0-100 MPH happens in about one second as well according to
"The Learning Channel" (< good source of info? :))

The 60' is indeed in the 1 sec. range, obviously it's a matter of traction not hp. I wonder how you would calculate the 60' if it were possible to "dead hook"?

Rich Krause

Originally posted by Zero_to_69
Uh oh...let me restate that:

Gotcha OldSS = Understood your explanation

Back to the thread!
That's how I took it. Not much paranoia here. :)

Originally posted by Zero_to_69
I "think" it's about 1.0 second for the 60 foot time.

0-100 MPH happens in about one second as well according to
"The Learning Channel" (< good source of info? :))

A 1.0 sec 60 ft. time equates to about 3.7 average g's.

A 1 sec. 100 mph time equates to about 4.5 average g's.
That would equate to a 60 ft. time of about .82 seconds.

4.5 g using only tire traction ain't bad. Well, by 100 mph there is significant down force.

4.5 g on a 2200 lb car(?) is about 10,000 lbs of thrust. With a 16 inch loaded tire radius, I get 12500 lb-ft. at the tire. With a 3.20 screw thats about 3900 lb-ft getting thru the clutch. That's about where I figured torque at 8000 rpm. That's close to a "dead hook". These are averages for the first second or so and we're estimating hp's of course. My guess is that tire traction technology and hp production are running in step.

FWIW, With 12500 lb-ft at the tires, why no wheelstand? The front wheels are 300 inches or 25 feet away, so 500 lbs on the fronts will balance the 12500 lb-ft. If a TF car is about 23%-77% static distribution that's about 500 on the fronts.

I think I got the math right.

A TF dragster will 60' around .80, a Top alcohol dragster will 60' in the low .90's. High 6 second/low 7 second cars usually 60' around 1 flat. I don't know about 1/8 mile ET, but on a good pass TF dragsters run over 270 to the 1/8, a Top alcohol dragster around 220.

Originally posted by OldSStroker


No, I wasn't referring to McVeigh, if that's where you are going?

No, I was thinking about Astrolite G and A-1-5.
(Hammas is supposedly experimenting with astrolite soaked clothing instead of the traditional bomb vest, as a way of being stealthier.)


McVeigh supposedly used ammonium nitrate and nitromethane anyway.

Not that I believe the govt's story. The crater under the truck wasn't consistant with a low brisance explosion (<21,000fps), the supposed design was about as inefficient as you can get and the BDA was inconsistant with the laws of physics anyway. Under the "official" version of the story anyway.

But I think that's enough off-topic public discussion on this "touchy" subject anyway.

If you want to continue discussing this subject, which is fine with me, I suggest we take it to PMs.

Originally posted by WickedFast555
A TF dragster will 60' around .80, a Top alcohol dragster will 60' in the low .90's. High 6 second/low 7 second cars usually 60' around 1 flat. I don't know about 1/8 mile ET, but on a good pass TF dragsters run over 270 to the 1/8, a Top alcohol dragster around 220.

Wicked's numbers are closer to real life. A 1.0 60' time for a fuel car would be way off the mark.

Does anyone know what the coeffeicient of friction between the tires and ground is? I remember in one of my physics classes they mentioned that is is one of the highest friction coeffiecients of any two surfaces in the world but they didn't have a number.

Originally posted by dkeers
Does anyone know what the coeffeicient of friction between the tires and ground is? I remember in one of my physics classes they mentioned that is is one of the highest friction coeffiecients of any two surfaces in the world but they didn't have a number.

According to Milliken & Milliken in Race Car Vehicle Dynamics:

"The rubber is stuck to the road by a variety of mechanisms including mechanical 'gearing' to the texture of the pavement and molecular adhesion to the surface. These mechanisms are not totally understood."

If you assume ~4.5 g's at launch with negligible downforce, the effective coefficient of friction would be ~ 4.5. (edit) See brent's post below...

I like this quote, perhaps from Maurice Olley(one of my heroes, FWIW):

No living thing but a snail has as good a shoe as a motor car

Originally posted by OldSStroker

Note that burning occurs thruout the power stroke and most of the exhaust stroke. The excess fuel burned in the upturned headers give a significant amount of download onto the tires.


I was going to comment earlier how interesting and significant i found that. Because the tarmac is smooth the mechanical gearing aspect can't be very large. The molecular adhesion of hot sticky rubber alone isn't coming close to bumping that up to 4.5.

-brent

Originally posted by 94formulabz
I was going to comment earlier how interesting and significant i found that. Because the tarmac is smooth the mechanical gearing aspect can't be very large. The molecular adhesion of hot sticky rubber alone isn't coming close to bumping that up to 4.5.

-brent

Good thought. A couple of thou downforce would halve the apparent mu, wouldn't it? ~2.5 sounds more plausible, huh?

to the people comparing it to the 747, that's 240,000 pounds of thrust, not horse power you have to do a conversion that escapes me at the moment to convert it to HP

To answer:
to the people comparing it to the 747, that's 240,000 pounds of thrust, not horse power you have to do a conversion that escapes me at the moment to convert it to HP

I submit from Page 1


240,000 lbs of thrust. If we assume a speed of 330 knots that is 240,000HP

:)

Chris

i want to mix some of that nitro in my gas tank :eek: :D

Originally posted by Maldo
i want to mix some of that nitro in my gas tank :eek: :D

I would guess it would have the same effect as putting 94 or 110 in an engine made for 87, would burn too slow for the compression to do anything, but I could be wrong since it is a totally different fuel.

Originally posted by jonaddis84
I would guess it would have the same effect as putting 94 or 110 in an engine made for 87, would burn too slow for the compression to do anything, but I could be wrong since it is a totally different fuel.

Couple of points -

Octane rating has no correlation to flame speed. Octane rating is just a measure of the amount of energy required to begin oxidation(burning). A higher octane fuel can have a higher *or* lower flame speed, it depends on it's constituent proportions.

Also nitromethane burns much faster than normal gasoline.
Gas is about 0.35 m/s at stoich, while nitromethand is about 0.5 m/s at stoich (flame speed).

To mix gas and nitromethane in any appreciable quantities you will need some sort of emulsifying agent - there are quite a few products out there that can do this though, so no problem. You can probably get up to about 10% by volume. Nitromethane will mix much better with methanol.

The problem would be the change in a/f ratio. Nitromethane is stoich at what, about 1.7:1 I think, while gas is 14.7:1. By replacing 10% of the gas (by volume) with nitromethane, we have just effectively change our overall stochiometric ratio. Added a bunch of oxygen. So you are going to have to spray in a good bit more fuel if you want to stay on the rich side of stoich/utilize all the oxygen you have in the cylinder. You could definitely calibrate your engine for this. Now the problem is what do you do when there is no nitromethane in there? Either run a new calibration, or don't run (or run *very* rich).

So unless you are just trying to be sneaky it is much simpler/easier/safer to put a nitrous oxide kit on there. And combusting nitromethane has a very distinct smell, though I don't know how distince at 10% - but chances are it would be pretty detectable.

Chris

Originally posted by Chris B
Couple of points -


Also nitromethane burns much faster than normal gasoline.
Gas is about 0.35 m/s at stoich, while nitromethand is about 0.5 m/s at stoich (flame speed).Chris Hmmm. That's the opposite of everyting I've heard. I did find one repeating reference that confirmed the .5 m/s nitro burn rate, but I couldn't find any other reference backing that up. Of course fast burn, like in explosive stuff is more like 6500 m/s.

I'm curious as to why, if nitro burns faster, it requires lots more ignition advance than gasoline and continues to burn longer in the cylinder.

At 8000 rpm or 133.3 revs/second, one complete revolution takes 7.5 milliseconds. In that time, at .5 m/second, the flame would move about .0075(sec) x .5(meters/sec) or .00375 meters or .148 inches. I'm confused big time now. Help me out here.

A little more on TF acceleration:

Here's an interesting article on Dragster Science:

http://www21.brinkster.com/jimsideagarage/dragster/dragstersci.htm

I found the acceleration curve interesting. Even though they are using short term averages and quoting acceleration in "mph/second", you can convert to gs by multiplying the mph/s by .04554 which is (88 fps/60mph/32.2fps^2/g).

That gives 2.38 average gs for the first .88 sec and 4.39 average gs approaching the 1/8 mile point before the induced drag from the rapidly increasing downforce and aero drag cuts back the accceleration to 1.56 gs near the traps.

Originally posted by Maldo
i want to mix some of that nitro in my gas tank :eek: :D


Wouldn't Nitromethane also eat away at fuel lines and float, etc?
Just like with alcohol cars, you'd have to convert the fuel system correct?

It's also a fact that using a high octane fuel in a low compression
motor is going to make the ignition work that much harder to ignite
the mixture.

I was told that the fuel octane should be enough that under the
most extreme conditions, it's on the verge (<<< or close to) of pre-ignition.

This makes the efficiency of the ignition system higher.

Any truth to that theory?

Originally posted by OldSStroker
I
[...]
i'm curious as to why, if nitro burns faster, it requires lots more ignition advance than gasoline and continues to burn longer in the cylinder.
[...]


Good question - I have not alot of direct exprience with running nitromethane in large 4 stroke cars (little 2stroke gas/RC engines have done it a bunch though :) ) - About the only thing I could come up with would be something due to the much greater fuel volume or the greater cooling effect (vs. gas)

On a methanol motor do you know how the timing requirements change when you add nitromethane?


It's also a fact that using a high octane fuel in a low compression
motor is going to make the ignition work that much harder to ignite
the mixture.

I was told that the fuel octane should be enough that under the
most extreme conditions, it's on the verge (<<< or close to) of pre-ignition.

Nah, for the most part the amount of energy in the ignition charge is already much much greater than needed to initiate oxidation. The fuel itself doesn't have a big difference on how hard it is to initiate the spark (excepting top fuel type situations, where the cylinder has a tremendous amount of liquid in it) - for most situations the cylinder pressure will have a bigger effect.

Damnit! i hate this pos server eatin my posts. but anyways, this thread is a good one. the downforce from the pipes is pretty substancial, u can see them correct with the wheels when one of the cylinders goes. also, i saw something about how the plugs are destroyed? bs. i have a set of funny car plugs and they are in great shape. the gap is tight as hell too, .018. i also snagged a clutch plate, those things are friggin toasty when they come out of the car, had to hold it with a rag for a few hours after the run.

Maybe this talk about electrode errosion after the run is confused
with "side gapping".

Where the electrode is purposely fabriated/cut away to expose
the spark to the mixture.

I recall watching a tech team rebuild a pro-mod alcohol car before
a run, and the plugs where sitting on the bench.

The electrodes were short and came in proximately from the side
as opposed to the top.

Tough to explain without a photo; know what I'm sayin'?

dude i have 2 sparks from them and a head. the electrodes are gone on the plugs that i have btw ther ar autolite AR50 plugs

damn man, howd you come away with a head?

the plugs i got were champion N1032Y. i dont get totally what you are saying about the electrode coming in from the side, the plugs look just like normal plugs but huge. haha

paid 200 doallrs for it i also got a piston/rod and the sparks for that price the rods they use are freakin huge i cant even rap my hand around it

someone said they don't use head gaskets


they use copper head gaskets and the head has been o-ringed to it (gopper gasket has ring on it hard to explain)

a fuel car that has an et 4.6xxx they are producing over 7000 hp

to turn a top fuel blower you need ~ 400-450 hp

Originally posted by Chris B
To mix gas and nitromethane in any appreciable quantities you will need some sort of emulsifying agent - there are quite a few products out there that can do this though, so no problem. You can probably get up to about 10% by volume. Nitromethane will mix much better with methanol.

The problem would be the change in a/f ratio. Nitromethane is stoich at what, about 1.7:1 I think, while gas is 14.7:1. By replacing 10% of the gas (by volume) with nitromethane, we have just effectively change our overall stochiometric ratio. Added a bunch of oxygen. So you are going to have to spray in a good bit more fuel if you want to stay on the rich side of stoich/utilize all the oxygen you have in the cylinder. You could definitely calibrate your engine for this. Now the problem is what do you do when there is no nitromethane in there? Either run a new calibration, or don't run (or run *very* rich).

Chris

Hmmm... this really caught my attention. Speaking of the use of nitro in a street machine.... A couple of years ago i was planning to try mixing some nitro into my alcohol injection system in the GN. I asked around but no one could give me a definite answer as to what all would be involved in this. Not even the TB community could offer any real help. Right now i can run 17psi boost on 93 octane alone. Injecting straight ethanol(100% denatured) allows me to run 25psi before it starts detonating again.

Now lets say i change out the lines and pump so i can run methanol. With a 90% meth/10% nitro mix, how would the car act? Blow up? More/less boost capable? Would i be better off leaving the nitro idea alone?

With the power locked inside of nitromethane, it's use in street cars (if it can be made practical) would seem to be the next hot ticket.

if i were you i wouldn't run 10% nitro. if you have a 16 gallon tank full of methanol put 1 quart of nitro in not sure don't have a calculator but its probably like 1-2% nitro. it might lean you out a little but burning nitro you won't detonate with just the little bit of leaning. and switching from 93 to meth/nitro i bet you would see 150+hp gains :eek: now i wouldn't do it very much unless you like building engines :D

they had an article in hot rod mag awhile back about a buildup on a smallblock using a alcohol/nitro mix. made some impressive #s, i think the max nitro they used was like 10 or 20%.