Quote:
Originally posted by scargo70
Why is a flat torque curve important?
With most HP curves seem to have a upward slope while the torque "curve" is usually flat.
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A flat torque curve usually means that there is lots of torque available at low rpm, which means lots of "grunt" and acceleration. If you draw a graph of the equation I posted above, HP will increase with a totally flat torque curve thanks to increasing rpm. At some point the engine cannot breathe in any more air or fuel and the torque curve starts to fall off. Then, even rising rpm cannot save the HP, and it too begins to fall off.
Suppose we have 300lbs-ft of torque at 1500rpm and 300lbs-ft of torque at 4000rpm.
HP = torque * (RPM / 5252)
= 300*(0.2856)
=85.7 @ 1500 rpm
HP = torque * (RPM / 5252)
= 300*(0.7616)
= 228 @ 4000 rpm
Completely flat torque curve, dramatically rising HP curve.
Engine RPM is limited by many things. There are mechanical limitations that include the ability of the valve springs to close the valves, the speed the piston can move up and down, and so on. There are fule/air related limitations that involve the amount of mixture that can be moved into the chamber and the amount of exhaust that can be removed.
Horsepower is the ability of the engine to do work over time. The time thing is very important in the definition. Torque is the amount of force, and hp is the amount of work over time.