For dyno purposes...

...what is the drivetrain loss to the wheels? At first I was under the impression that it was 8%. Lately though, I've heard different. Whats the story?

Originally posted by USHotRod
...what is the drivetrain loss to the wheels? At first I was under the impression that it was 8%. Lately though, I've heard different. Whats the story?

If I remember correctly, I think its like 10% for an M6 and like 18% for an A4. I could be wrong, but thats what I remember.

12-14ish m6 and 17-19ish a4

Number's I've heard are:
13% for M6s
15% for A4s
GM's drivelines are very efficient.

350FWHP*.87=304.5RWHP
350FWHP*.85=297.5RWHP

Those numbers fall right in line with what I dynoed.
297.5+9(optional SLP exhaust)=306.5 (very close to actual 306.9)

So in other words, our cars should really be rated from the factory with @375 hp at the crank? Wow....:D

Originally posted by USHotRod
So in other words, our cars should really be rated from the factory with @375 hp at the crank? Wow....:D

I think about 345 is a little more accurate.

Originally posted by CrippleFightin
I think about 345 is a little more accurate.

Well how is that when LS1's dyno in the low 300's with between a 15 and 19% drivetrain loss? (A4)

So...lets say 300rwhp bone stock.

15%=@354
16%=@358
17%=@362
18%=@366

Yeah, so my 375 was a little optimistic but these seem to be pretty good guidelines given those percentages.

Originally posted by USHotRod
Well how is that when LS1's dyno in the low 300's with between a 15 and 19% drivetrain loss? (A4)

So...lets say 300rwhp bone stock.

15%=@354
16%=@358
17%=@362
18%=@366

Yeah, so my 375 was a little optimistic but these seem to be pretty good guidelines given those percentages.

Its usually the M6 that dynos a little over 300rwhp. The A4 is 'usually' in the 290's. Of course this isnt for everyones car, but its more common.

OIC. :p

I always use:
12% for M6
and
15% for A4

Originally posted by danno02SS
Number's I've heard are:
13% for M6s
15% for A4s
GM's drivelines are very efficient.

350FWHP*.87=304.5RWHP
350FWHP*.85=297.5RWHP


Exactly the same thing we use here in the club and the same numbers Hypertech uses for our cars.

Michigan State University's Dyno Lab and general Automotive Engineering usage (GM, Ford) is 10% Manual, 13% Auto for RWD.

Using these #s, you will find that the published HP ratings for the LS1/others are quite accurate given our dyno'ed RWHP data.

Using anything above 13% is just plain fooling yourself, unless you think bench-racing is all there is....