I'm planning on dynoing my car after the Stage 4 GTR kit is installed...
if the dyno machine is SAE... and it's RWHP that I get...
what's the estimate real HP on crank?

 

Most will quote a 15% drivetrain loss from crank hp to hp at the wheels. This is only an estimate. There are extensive discussions on this previously. You may want to do a search. Its imp if the dyno is two wheel or four wheel. I think 4 wheel dynos give lower numbers.

 

4wd's tend to lose about 25% but these are all estimates, and what's really important is the car's rwhp.

 

In terms of drivetrain loss, generally, 15% is used for FR (front engine rear drive) cars and 20% for AWD.

The most common way to actually measure drivetrain loss it is to use the dyno to measure it... I believe it's done while the drivetrain is coasting down, as the dyno compares it's known momentum (and/or drag, hence deriving the time it takes to coast down) against the difference when a car's drivetrain is introduced into the equation. This is an over-simplified explanation, but you get the idea... it's kind of a "reverse" dyno pull.

Then, one has to take into consideration altitude, temp, etc... for the final correction.

Stephen
'01 Turbo Ti
1stephen1.com

 

While it is true that an automatic tranny 4wd truck may experience a 25% drivetrain loss, our Turbos' drivetrain are much more efficient than that. I'd imagine it's somewhere beteen 15~20%.

Stephen
'01 Turbo Ti
1stephen1.com

 

thanx guys ^_^