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Old 07-26-2020, 11:18 AM
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eschaider eschaider is offline
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Join Date: Feb 2006
Location: Gilroy, CA
Cobra Make, Engine: SPF 2291, Whipple Blown & Injected 4V ModMotor
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Conceptually you are spot on Tiony. Mathmatically you missed by a fat finger press probably.

Horsepower is torque per unit time divided by 5252, as you indicated. The formula is;

HP = (TQ * RPM)/5252

We can do a little algebraic reshuffle of the basic formula to solve for TQ instead of HP. To do that we need to first multiply both sides by 5252 to remove it from the right hand of the formula. When we do the formula becomes;

HP * 5252 = TQ * RPM

Now we can easily solve for TQ by dividing both sides BY RPM and we get;

(HP * 5252)/RPM = TQ

I suspect the FR9 engine hits peak power at 7000 to 7500 RPM with a max engine speed of 8500 maybe 9000 RPM — this is after all a purpose built racing engine.

If we use the 7500 RPPM number and plug in the original numbers he claimed (before changing his opening post) to the TQ solving version of the formula we get

(900 HP * 5252) / 7500 = 630 ft/lbs of TQ

Not all that much although still impressive, particularly for the engine displacement and the rpm it can deliver it at.



Ed
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