ironheart1 said:
Horsepower vs Torque is a funny thing, really. I don't quite understand it save for this explanation: Horsepower is a measure of the energy your engine produces while torque is a measure of the force your engine produces. I don't think that how long you're producing power for depends on your horsepower so much as your setup and your stroke.
From the CM Performance website(I cringe)
Horsepower
What is horsepower (HP)?
James Watt made some pretty hot steam engines before we were born (get the "hot" pun?). Anyway, he needed a way to measure the power output of them, so he hooked his horse up to one of those pumps that you turn the lever around in a circle to make it pump. He did all the math figuring how fast the horse was going and how much torque it put on the pump over 1 minute, blah blah, and came up with a horsepower number of 550 pounds per feet per second.
HP = RPM * torque /5252
RPM is revolutions per minute
Torque is in ft pounds
5252 takes care of converting all the units from Watts' 550 pounds per feet per second.
By the way, 746 Watts (electrical) = 1hp.
You can fiddle with this formula to solve for rpm or torque too.
example: torque = HP * 5252 / rpm
example: rpm = HP * 5252 / torque
What is BHP or brake horsepower?
This is HP measured at the crankshaft of the engine, with no fan, air cleaner, alternator, transmission, air conditioner, basically nothing but the engine. This how most manufactures rate their engines, and it is pretty much crapola. Rear wheel hp (RWHP) is what your making at the wheels, what your putting to the road, and it should be all you care about, because that is what moves your vehicle. All our dyno charts are true RWHP. A lot of dyno shops up the RWHP that they measure by 15-30% (estimating losses of trans, alternator, whatever), and try and give you an BHP number. Yes, it gives you a bigger number, and yes, your a sucker to believe it. How do you know if those power pulleys, new tranny, lightened flywheel make a difference if someone is fudging your numbers from dyno to dyno? Don't let them do it, and don't let someone show you a chassis dyno curve that indicates BHP.
What is corrected HP?
Corrected Horsepower is a way to equalize dyno readings across temperature, barometric pressure, and relative humidity. All these conditions affect the way your car breathes air and makes power. Does your car feel snappier on a cold day? It's because the air is denser, so your car gets a bigger gulp of air as compared to a hot day, and makes more power. Ever drive in the mountains and feel like your car lost 2 cylinders? As you go up in altitude the air gets thinner, so your car can't get as much air to make power. Same thing happens to me when I go hiking. Anyway, the SAE (society of automotive engineers) got together and figured out how all these factors affect HP, and we can apply some simple math to our dyno results to "correct" for the atmospheric conditions when the test was done. If everyone corrects to the same standard conditions, then we can compare dyno results from day to day. All our dyno charts are corrected to SAE 29.6"Hg 77 deg F wet conditions.
-Mike
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