HP rear wheel or flywheel

[mark kibort <mkibort@xxxxxxxxxxxxxx>]

Message text written by INTERNET:bmw@domain.elided
>So............whats the deal?   Are these cars over rated from the
factory?
Is there more driveline loss than in a Porsche or 300ZX TT,etc...?

Just curious...

Thanks
Rob<


Rob,
good question, but it seems to be a battle of spec'manship. Ive done plen=
ty
of dynos
and Ive found that I can use a divide by .84 calulation to match most
factory spec's.

in the most efficient drive trains , with a one stage reduction.  (like a=

rear end when you
testing the vehicle 4 th gear, or a 1:1 gear), you have to have at least =
a
85 % efficiency =

level.   On the dyno, you can decel and find rolling friction and rear en=
d =

losses =

  as  they are in the 8% range alone without the  transmission losses. =

 (this is because you can't disconnect the drive train from the engine
without using the clutch =

 and the clutch would provide too much friction.    (I might try that
anyway next time)

Anyway, the factory specs are meaning less as Ive seen stock 928s, 911, a=
nd
944s all over =

the map usually more than the calculated HP  from the factory.  BMWs  and=

US cars are
 usually closer to factory specs after you divide by .84.  =


Just based on a dyno day observation that tested 80 cars from BMWs to
mercedes to Vets to =

all sorts of Porsches.

I love the look on the guy that has done a ton of work , and the dyno rea=
ds
50 hp less than he
thinks he should have.   I used to be that guy.  Now, before I guess, its=

off to the dyno!!

Mark Kibort

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