Calculating peak torque

[chris davey]

Peak torque = (HP X 13000) / (capacity in litres X RPM)

The other way you can work this out is to get a flat AFR line and whereever the most fuel is being injected is the peak torque figure. I have done some calcs from both of my dyno runs just to see the difference.

Cylinder Pressure HP RPM
130 80 3200
130 95 3800
161 136 4400
202 195 5000
215 219 5300
215 221 5360
213 224 5480
215 232 5600
212 240 5900
205 244 6200
183 239 6800
154 219 7400




113 52 2400
127 76 3100
126 92 3800
157 136 4500
224 224 5200
249 256 5340
266 280 5480
274 296 5620
276 306 5760
279 316 5900
252 320 6600
233 318 7090

I know that is hard to read but basically you can see that the torque numbers have increased. I am not sure if it is 100% correct but is that the cylinder pressure? So on my first dyno, peak was at 5300-5600 and the second it was at 5600-5900.

[kingmick]

Well work out this one and i can tell you your right exactly from the engine being on the engine dyno.
650hp,6 litre,8000rpm

i work in foot pound

[chris davey]

aah yes, forgot you are supposed to use engine dyno figures to have correct numbers. I figured that you must be getting pretty close with the chassis dyno numbers. Not to correct numbers but just determining where the peak is.

I get 176 for your calc which I suppose is pretty good for a pushrod v8 hey? I can't remember what the book said was expected. 210 or so for a full race cosworth engine. As you would expect, turbo engines should have higher numbers than n/a.

[kingmick]

ok Atmo cause you cant race anything else circuit in 6 litre
its 580fp from 3800rpm.

[kingmick]

or turbo with the 2.3litre V6 is 813hp at 8000rpm on the engine dyno in circuit racing long lasting trim if that makes it easyer to work out.

[kingmick]

or the jag in my avtar was 580hp at the wheels{chev} 6litre 7800rpm with the slicks melting on the dyno

[kingmick]

P.S either you read the book wrong or it is miles out . Thats the trouble with 99.9% of books on racing and engines, there many years behind

[chris davey]

Hehe, forgot about this thread. Umm, I think this calculation is used to determine the peak cylinder pressure (in psi?) not the peak torque the whole engine is making.

That would make more sense to me as to why the numbers I have are nothing like yours.

I wasn't actually using the numbers for anything just to see where the max value is to determine ignition timing ramp up.

[YelloRolla]

ok Atmo cause you cant race anything else circuit in 6 litre
its 580fp from 3800rpm.

That's a pretty nice engine that you're talking about there Mick. 580ft/lbs at 3800 = 420hp and the torque value at 8000rpm (assuming 650hp) is 426ft/lbs. This baby is making a nice fat power curve.

[Skip]

Chris,

I marked the peak torque spot on your dyno graph with a little red point i.e. the highest point of the graph with the steepest gradient.

Torque = Power x 60 / 2PiN

for yours = 215x1000x60 / (2xPix5480) = 375 Nm @ wheels

[kingmick]

That's a pretty nice engine that you're talking about there Mick. 580ft/lbs at 3800 = 420hp and the torque value at 8000rpm (assuming 650hp) is 426ft/lbs. This baby is making a nice fat power curve.

Yep it sure does, i nice flat line