? about engine power/throttle/rpm

[OS]

At a fixed RPM value, how much does the throttle affect the power output of an engine? For example, say you have at some moment in time, you have an engine running at 3000 rpm. In case A, you had the gas pedal floored, while in case B, you had only light pressure on the gas pedal. How much power difference at 3000 rpm would there be in case A and B?

The reason I ask is cause I was merging onto the freeway today and had the gas pedal at some leisurely position. I was suddenly going 80 and I was a little surprised because I was going real easy on the gas.

 

[fastz28]

You can't have the same rpm with variable throttle, unless you are in a different gear.

 

[OS]

<< You can't have the same rpm with variable throttle, unless you are in a different gear. >>



well, I don't mean keeping the rpm constant though. Say if you floor it, you'll definitely pass through 3k rpm. If you go easy on the gas, you'll probably also pass through 3k rpm. So in both cases, at the instant they are both spinning at 3k rpm, how big is the power difference?

-i have sucky grammar

 

[shaddow]

unless your car has an overdrive button in which your car holds you in a lower gear longer for better acceleration

 

[notfred]

take your car to a dyno and try it.

 

[fastz28]

Ok, understand your question. First, formula for horsepower=torque*rpm/5252.

A car will accelerate hardest at its torque peak in a given gear. Torque is the only thing that you feel, and horsepower is just a calculated #. 200 ftlb of torque will accelerate you just as hard at 3000 rpm as it would if you were making that torque at 6000 rpm in the same gear, but the horsepower would be *double* at 6000 rpm. Therefore, horsepower isn't really meaningful from your perspective.

Bottom line is, if you know your torque at a particular rpm, you can calculate hp. You need to get on a dyno to get your torque at the given rpm.