Real HP loss numbers

[David Piper]

On my DynoJet, from coastdown measurements, we have measured from 10 to 28
HP loss in drivetrain with straight drive tranis.  The 10 hp was on straight
drive 280Z with smaller R180 open rear diff with new spicer UJ and synthetic
lube in 4th gear (1:1).  Most Z's are around 17HP at 6K RPM.  A Cobra
replica straight drive had 28 HP.  An auto on a drag car with big Dana rear
had 150HP loss at 7400RPM.  The Ford 5.0L manuals are around 20 HP.
Measurements are RPM dependant.

Engine motoring produced around 90HP incl drivetrain loss on the Z's and
120HP on 350ci chev (Corvettes) and 150HP on big blocks.

These figures are based on inertial effects as well as frictional losses.
Additional load is imposed on the front wheels and by aerodynamic load which
increases as the cube of speed.  Hence, final tuning must be done with
actual road testing, otherwise load enrichment will be insufficient.  

The value of the DynoJet can be fully realized with real time data
acquisition measurement of engine parameters such as boost, fuel flow, fuel
press, exh gas back press, intake charge temp and EGT, etc.

NASCAR uses it for final shakdown b4 loading on trailer, drive train loss
and vibration analysis.

TurboDave

At 01:02 AM 3/12/99 EST, you wrote:
>Was wondering (induced by all the talk with computers recording spark signals
>and computing HP) what are the actually losses in drivetrain.  I've heard the
>torque converter is 97% efficient at part throttle and 2 hp at U-joints (I
>don't believe, that's 1500 Watts at each joint).  Looking at tranny (auto and
>standard) u-joints, ring and pinion, bearings, spider gears, axles....
>
>Sorry, it's off the beaten path, oh well    :)
>
>Mike
>
>