"kneejerk negative response" (archive)

The estimate of drivetrain loss is an ex ante guess prior to getting your car dyno'ed. Once you have your dyno results, you can pretty accurately figure out your estimate drivetrain loss. Once you know your horsepower at the rear wheels, you can't just assume 15% and then use that to figure out actual horsepower. No, that doesn't work.

If he is getting 217horsepower at the rear wheels, and the M coupe engine is rated at 240 horsepower, then his loss is 1-(217/240) or 9.58%, not 15%. 15% could be a number you would assume before you dyno'ed your car.

In this case, you would make an ex ante assumption that your drivetrain loss would be 15%. You would expect your car to show 240-.15(240) or 204 horsepower on the dyno. Your result of 217 horsepower would then negate this assumption.

-Ben FR

Follow Ups:

Re: not correct (m) ben keyes 16:01 2/18/2001 (0)
Re: "kneejerk negative response" Dean 15:57 2/18/2001 (6)
- The 240 HP number can't be accurate.... MPressed 17:56 2/18/2001 (0)
- i am assuming the 240hp figure is accurate Ben FR 16:06 2/18/2001 (4)
  - assuming makes an ad hoc post facto ass of you! Marshall 20:05 2/18/2001 (1)
    - Speaking in an "ex ante" sort of way. Dino 08:50 2/19/2001 (0)
  - Drivetrain Loss For A BMW Is Typically Thought... dpeete 19:44 2/18/2001 (1)
    - Driveline loss for 90-96 Nissan Z's typically 18% Dean 20:07 2/18/2001 (0)

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