Another great read regarding rated HP on GM LSX engines.

http://forums.corvetteforum.com/show....php?t=1974770

 

It's pretty basic physics for why hp loss will increase with power throughput. There is both a constant, linear, and even second and third order factors to consider. Speed, torque and acceleration all matter.

Proof? Are you unable to spin a transmission by hand? Do you think you can generate 13hp with your hands on a little shaft?

The 4 cylinder type examples are relevant too. Unless you think a 100hp 4 cylinder needs a minimum of 50% throttle to begine to even move a V8 drivetrain.

I think trying to figure exact engine output from 'corrected' dyno sheets is a big waste of time, especially different dynos on different days in different air with different chassis and different sensors for temp / baro / humidity

 

I agree. I have always though along these lines but did not have the support to back my theory and never felt like arguing. It only makes since. If you swap engines in a car the loss of power could be greater/less but it would depend on a few factors. What if anything changed about the drivetrain other then the engine? How much weight if any has the setup added? Other then a few things the percentage should remain close to the same as you suggest.

 

That was a pretty good read on corvetteforum. I think the percentage numbers, especially 15-20% are a bit overplayed, especially on the higher horsepower modded cars. I think the bulk of the drivetrain loss comes from spinning the mass inside of it and as such unless you are accelerating it a lot faster you won't notice much power difference. So basically I don't think that when we are discussing cars with power and gearing that are within the realm of the street that these 2nd, 3rd, or 4th order terms to the drivetrain loss probably matter at all... which really means that they are likely on the order of a few horsepower and probably within the range of hte error in the dyno and a wash anyway.

 

Numbers that matter most to me are weight vs trap speeds. A good indicator of potential lies in the trap speed. Dyno's are good for getting maximum power. Nothing wrong with a nice dyno sheet to supplement arrogance but they dont mean everything.