In anticipation of an arguement

[big2bird]

Don't forget that the auto trans had a front pump. It takes some power too.

Yeh, but for a stick shift to suck up 15% of engine HP, and another ~10% for the diffy?? something like that.... it's nutz....

Add up the total "weight" of all revolving parts to be accelerated and maintained, and you'll find a 200lb+ flywheel. I would ASSUME the large difference between "engine" dyno readings and "RWHP" dyno readings to include these losses, since the test is done while accelerating.

 

[big2bird]

For arguements sake. (New guys)
RPM X Torque / 5252 = HP

 

[mrvette]

Don't forget that the auto trans had a front pump. It takes some power too.

Yeh, but for a stick shift to suck up 15% of engine HP, and another ~10% for the diffy?? something like that.... it's nutz....

Add up the total "weight" of all revolving parts to be accelerated and maintained, and you'll find a 200lb+ flywheel. I would ASSUME the large difference between "engine" dyno readings and "RWHP" dyno readings to include these losses, since the test is done while accelerating.

On a chassis dyno, never thought of it, but you are correct, it is...

but methinks your total rotating weight hanging on there somewhere is correct, including wheels/tires....I think the relative weight is much less further back in the drive train as you have gear reduction in the diffy at minimum....so ~3-1 reduction in effort for everything from the ring gear on out...:crutches:

 

[greg75vette]

Power loss with respect to transmissions is usually given in precent. There really isn't a fixed hp loss for any given powertrain. Usually manuals soak up about 10% (very low) to 15% and autos about 20-25%. It depends on the configuration but the big killer in autos is that big fluid coupling you have in the front of it: the torque converter.

Mechanical systems are done in efficiencies, so in effect, you're saying a drive train loss of, say 12%, really has a mechanical efficiency of 88%.

As far as AC, I'm sure the compessor engaged will be noticable, but the compressor disengaged is most likely not too significant. But that too, would be accounted for in percent. The value would just me much smaller.