JohnnyC

There have been a few questions about power and torque going around, so I thought that I would throw some math at it.

Here are some interesting IC engine power and torque equations from some of my old college notes:

Engine Power = (hm ) (hc ) (ht) (hv) (ra) (Vd) (N/2) (F/A) (Qhv)


Engine Torque = (hm ) (hc ) (ht) (hv) (ra) (Vd) (N/2) (F/A) (Qhv) (1 / 4pi)


Where hm = Engine mechanical efficiency (power in / power out)

hc = Engine combustion efficiency

ht = Engine thermal efficiency

hv = Engine volumetric efficiency

ra = Air density

Vd = Engine displacement volume

N = Engine speed in radians per second

F/A = Mass of fuel divided by mass of air

Qhv = Heating value of engine fuel

pi = 3.14

All of the efficiencies would be ratios in the equations with values of 1 being the highest obtainable efficiency.

The equations look rather simple in this form, but some of the terms (like combustion efficiency and volumetric efficiency) can be complicated to improve apon.

Exhaust and induction mods, for example, are a couple ways that we gain power and torque by improving the volumetric efficiency (and others).