Drive train power loss? - The Unofficial BMW M5 Messageboard (m5board.com)

johann · 13th December 2001, 19:06

My E46 M3 was dynoed recently it from the dyno graph I can read that in only has 10% power loss. That sounds a little bit to little.

Any ideas what could be reasonable and why the dyno show so little drive train loss?

Anyway my stock M3 had 310RWHP and 386,5Nm torque.

Cheers,
/Johan

tfung · 14th December 2001, 02:08

I was thinking about this.... don't you think the drivetrain power loss would increase over time as the clutch wears out?

johann · 14th December 2001, 02:57

Terrence,

If the clutch slips there will be a higher drive train loss than normal even if slips ever so little. Some of the power will be transformed into heat instead of pulling the car.

Cheers,
/Johan

Pio · 14th December 2001, 03:15

Yep, true. But, thats only if the clutch is slipping badly. If it still grips the drivetrain loss should not increase.

I hear the drivetrain loss can be anywhere from 15-20%, Johann that is one powerfull M3 you got there, what type of dyno was it?

johann · 14th December 2001, 17:36

Pio, By every % the clutch slips you'll have as much drive train loss, right?

I think the Dyno is made by Bosch.

Cheers,
/Johan

M5Laser · 14th December 2001, 18:00

Those are strong numbers.... don't complain!

johann · 14th December 2001, 18:07

M5Laser,

I am not complaining, just curious to know the fly wheel hp.

Cheers,
/Johan

AndyMenard · 14th December 2001, 19:15

15% is usually pretty typical... although many factors play a part in this ... like:

1) clutch
2) tranny
3) rear diff - not so much the gears, as much as how efficient the diff is at transferring torque and HP
4) and last but not least the dyno itself.

My M5 has been dyno'd at 335 RWHP which translates to about a 15% loss.

Using the same 15% logic my Cobra R has been dyno'd at 375 RWHP which translates to about 440 at the crank.