A better relationship is with Torque.....(long) (archive)

There is not as many variables as with hp. Even relatively unsophisticated and old engines will put out good torque vs displacement. There is a more linear relationship with torque vs displacement if compairing all engines. Assuming non boosted applications.

An engine is a big air pump with fuel squirted in at a 14.7:1 ratio. The larger the displacement the more air you can get into the engine, the more fuel you can burn at the ideal ratio. The more torque you can make. N2O and boost just crams more air / O2 into the chamber.

Horsepower is a function of torque x speed of the engine (essentially rpm). Here is where the exotics make more hp per cc than the older domestics. Stronger internals, better flow.... allowing higher engine speeds....giving more horsepower per displacement but usually not much more torque per displacement than a "crude" domestic engine.

Example:
Honda S2000 2L 240hp 153ftlbs = 120hp/L 76.5ft/L
Corvette 5.7L 345hp 350ftlbs = 61 hp/L 61.4ft/L
Hyundai Sonata 2.5L 170hp 166ftlbs = 68 hp/L 83ft/L

So you see although the hp per displacement is extremely variable. The torque per liter is relatively stable even between the "high tech" S2000, the "old tech" Corvette and even a Hyundai. In fact I wonder how the Honda boys would feel about knowing that a Hyundai engine has a better torque per liter output than their "super" engine.

Follow Ups:

Ahem! FWK-Z3 23:02 4/16/2000 (1)
- Good catch. CYT 00:21 4/17/2000 (0)

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