I would have to agree that it is somewhere in the neighborhood of 15 to 20 percent. Post up what you have done to the engine and your transmission, torque converter, type of rear end and gears.

I like the Dyno dimulators also but you have to put in EXACT info or its just junk in and junk out. The only other thing is that you cant really test for is variables like good ring seal, low tension rings, dry sump systems, vacuum compressors, or electric water pumps which can all add pretty significant numbers to the engine HP figures. But aside from that I have found them to be accurate to 5% in either direction which is still pretty damned good for what it is.

- Cudaman -