Author Topic: 318iS Driveline Efficiency / Losses (Read 2369 times)

bmwman91 · « **on:** April 21, 2012, 08:35:53 PM »

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!

DesktopDave · « **Reply #1 on:** April 21, 2012, 09:21:41 PM »

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.

bmwman91 · « **Reply #2 on:** April 22, 2012, 01:44:07 AM »

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).

MLM · « **Reply #3 on:** April 22, 2012, 02:16:07 AM »

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%

carnurd · « **Reply #4 on:** April 22, 2012, 01:05:06 PM »

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.

Author Topic: 318iS Driveline Efficiency / Losses (Read 2369 times)

carnurd