bryce804

i was looking at a dyno on an exhaust with a friend. and the power/torque crossed around 4k. he immediatly said its not a good dyno and to keep looking. he said that all dynos that are accurate the horsepower/torque will cross at 5200 rpm. is that true?

hamhead

Generally speaking, yes they cross around that area. That shows that its fairly accurate. Torque is a formula directly related to HP.

a_gut

I imagine this also depends on the camshafts, as there is only 1 camshaft profile best for a specific rpm, and not every car has variable valve timing, so I can see peak power and torque dropping off before before 5200rpm.

hamhead

Torque = HP / RPM plus some other crazy number thingies. Its not necessarily at peak power and torque where they cross. You could have an engine that the torque and HP lines cross well below peak. If you want to see some good dynos, go to AEM's website (aempower.com) and look at all their dynos. They all cross in the 5200RPM area.

turbulence

as far as i know, torque and hp will always cross at 5252. if you look at the hp equation (torque*rpms)/5252 = hp, you'll see how that works.

hamhead

Thank you! Gah I knew that formula but I couldn't think of it. Mucho props...

bryce804

so if the rpms dont really match at 5200 it is probally not a correct dyno? and i shouldn't trust dyno sheets unless they match.

hamhead

Yeah, the dyno is bad. I don't really see how it wouldn't cross @ 5200 unless it was like... faked or something.

bryce804

me either, guess this proves me wrong. ( had a small bet with a friend) thanks guys.