[s-cars] RE: [Audi20V_Kruemmer] Re: [UrS-technical] Driveline losses (was Tuning measured in DYNO at East Cost ?)

[mlp qwest]

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Thanks Jani -

I was under the impression the correction was computed by multiplying
wheel numbers by the transmission correction factor,
i.e. 376.7 * 1.25% tcf = @ 470.9

Shows you what little I know.  A second question I've wondered about
is whether the programming on the dyno that generates the numbers
also includs adjustment factors for altitude & temperature.

Last, on Frank's earlier point mentioning Corkey Bell's commentary on drive
line losses.  I've always had a question about applying a "fixed" percentage
to the calculation.  In fact I can recall a phone call Frank & I made from
his office going on now probably more than a year ago to DynaPack
asking them about their recommendation for 25% to be applied across the
board to any, and all Quattro drive trains.   There position was "Yep,
its a fixed, constant number...., and based on our (Dyna Pack's) testing
with 100's of Audis, we know our number, and our number is ... 25%."

My problem, using Rod's numbers just as an example, is you have two
identical cars as far as weight and driveline configurations are concerned.
One stock, the other tweaked with a bigger turbo, injectors, FMIC etc.

If we're to believe Audi's numbers for the stock car, it (should be) making
 @ 227 bhp at the crank, or 227 = X / 1 - 0.25.  X being in this case
@ 170.25 wheel hp for driveline losses of 227 - 170.25 = @ 56.75 bhp.

Now along comes Rod's engine modifications, and suddenly the cars
driveline is consuming 502.4 bhp - 376.6 = 125.6.  That's a difference of
@ 69 bhp within an otherwise identical driveline.  Isn't bhp just another
way to say "Heat" i.e., calories?  The conversion program I have
tells me 69 bhp = 12,300 calorie/second =  2,928.7 BTU/minute.

Isn't that an awful lot of additional heat the driveline alone has to
absorb?  & By driveline, would I be correct in assuming this is for
the drive line alone, not additional frictional losses in the internal
engine components?

I don't know that Corky is advocating a "fixed" number for tcf.
If I understand Frank's point, I think Corky's on your side of the
analysis of the MTM dyno "roll down" test, i.e. it is a variable
calculation.

I think what Frank has pointed out is Corky's saying transmission losses
 increase with bhp, just not in a linear fashion.

Mike
  -----Original Message-----
  From: jani.peltopuro at poyry.fi [mailto:jani.peltopuro at poyry.fi]
  Sent: Monday, January 13, 2003 6:28 AM
  To: mlped at qwest.net
  Cc: Audi20V_Kruemmer at yahoogroups.com
  Subject: [Audi20V_Kruemmer] Re: [UrS-technical] Driveline losses (was
Tuning measured in DYNO at East Cost ?)


  Hi Mike & other I5 hi-po freaks :-)

  regarding the driveline loss, the formula is:
  CrankPower x (1-driveline loss) == WheelPower
  so you get:
  CrankPower == WheelPower / (1-driveline_loss)

  ie with assumed driveline loss of 25%: 376.7/0.75 == 502,3. Same principle
  for torque. Very impressive numbers, congratulations Rod! Even with very
  conservative correction it is RS6-league power, nice with only 5 cylinders
  and 2.2 litres, and less weight.

  About Frank's passed message from Corky Bells book, that driveline loss is
  not relative to power, but constant: I doubt it, oversimplyfies things.
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