M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: bmwman91 on April 21, 2012, 08:35:53 PM
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How much power are we losing between the crank & wheels? For RWD cars there seems to be some "15% rule" out there, although that seems like it could be low. My first 318iS laid down 131RWHP, and with the chip & stuff I assume that it was making around 146BHP (134 stock, +12 from chip). That is only an 11.5% loss, which seems really low. Has anyone here dyno'ed an M42 on the bench, and then in the car with a stock tranny & an LSD? I am curious to see how much power is lost to friction in the driveline!
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I hope someone knows...it'd be great to have this information for builds.
You'd have to bench test an engine for this kind of info, I'd figure.
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Welll, assuming that Metric Mechanic can give me a dyno sheet for the motor I am having built, I can probably toss the car onto a dyno this summer to get a comparison. it would be SWEET if the losses were only 12%! I'll keep my fingers crossed though, because 20% sounds more realistic to me (wild guess).
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Im pretty sure driveline loss can be calculated while on the dyno by doing a wind down run. Not sure how this works but will give a result for your particular car.
Losses will be different from car to car depending on oils used condition etc however the rule of thumb i have heard of is 20%
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Well when it comes to DT losses our setup is not all that amazing. the losses should be around 15%. Some car's like corvettes have around 11-12% loss due to use of a torque tube and transaxle.