Quote:
Originally Posted by apexi
Long story short, the dyno is primarily meant to be used as a before/after tuning tool that can give you consistent results and NOT as a tool for absolute measurements to compare "power" from one member's car in Cali to one in NY which can be almost random/near meaningless.
Furthermore, drivetrain losses are not static-state fixed % that can be used to derive engine HP from a dyno reading. But we of course all do it using the standard rule of thumb of 15%MT-20%AT. Based upon my experience, although drivetrain losses are a crude way of trying to estimate engine HP from a dyno, it normally isn't substantially far off from manufacturer's specs for MOST vehicles.
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Excellent topic which I am glad has been raised by an end user for once.
I have covered this topic before on forums and not many people have taken notice of how dyno numbers can vary.
The purpose of a dyno is to measure the delta in measured power as part of a development programme or for getting an estimate between one particular setup to another.
As for the drivetrain loss - I think it would be helpful if I started posting readings from different cars and you can compare them to the M3.
We can go into far more depth by analysing correction factors, strapping etc etc.
Again, thank you so much for bringing this up!