JohnCL9999

Can anybody explain in plain english why dyno sheets always compare the torque and hp curves? I would really like to be able to use the info effectively. A buddy of mine tried to explain it but he got real technical about gearing and I didn't get it. Any help would be greatly appreciated. Thanks.

Argonaut

There is a fundamental formula: HP = T * RPM/ 5252

A dyno does not measure Horsepower. It measures Torque (twisting force) and the HP printed on the dyno sheet is derived from the torque using this formula. Notice at 5252 RPMs Torque = HP, this is where the curves cross. Its the same on every dyno sheet regardless of if the car is a Viper or a Honda (unless some sort of factors are applied in the conversion).

In real life - Torque is what causes you to feel the back of your seat when you nail the go pedal. Horsepower is a measurement of where in the rev range the vehical makes its torque. So even a motor that makes little Torque can make a lot of HP if you can spin it fast enough. Example: take a motor with 100 Ft-Lbs of Torque, a modest amount. But say it will rev to 20K RPMs. Now calculate the HP = 100*20000/5252 = 380HP. Wow!Higher HP means you are spinning the wheels faster (higher RPM) and thus going faster.

So both measurements are valuable. For day to day driving its Torque that is most important. It is the FUN factor you feel in your butt when you nail the throttle. For Drag racing both are important: Torque gets you going but its high HP (i.e. making Torque at a high RPM) that provides you speed.

Hope this helps.