Why is drive line power loss measured as % and not HP
03-13-2002, 08:04 AM
#1
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Why is drive line power loss measured as % and not HP
It seems strange to me that people subtract a certain percentage from the flywheel HP to get the wheel HP. I wonder if anyone can explain why it is a % and not a fixed HP loss (ie -40HP)
Since the parts you are accelerating always stay the same mass (ie flywheel,drive shafts, etc), then increasing the engine HP via a chip or other means, the drive line loss I expect to remain the same not to increase.
Is the % just a guestimate of sorts?
How does someone get the real drive line loss?
Thanks for any input.
Steve
Since the parts you are accelerating always stay the same mass (ie flywheel,drive shafts, etc), then increasing the engine HP via a chip or other means, the drive line loss I expect to remain the same not to increase.
Is the % just a guestimate of sorts?
How does someone get the real drive line loss?
Thanks for any input.
Steve
03-13-2002, 08:12 AM
#2
Because the drive line power loss changes with HP.....
If I had 300HP at %10 loss, I would have 270HP at the wheels, I lost 30HP. If I had 400HP at %10 loss, I would have 360HP at the wheels. I lost 40HP. See it now?
03-13-2002, 08:20 AM
#4
Take a look at this (long) thread for some insight.
I personally think that you are correct about this...or at the very least, there is a static component and a variable component to loss, with the variable component making up a smaller part of the overall loss than the static component.<ul><li><a href="https://forums.audiworld.com/performance/msgs/39208.phtml">Old thread about driveline loss.</a></li></ul>
03-13-2002, 08:42 AM
#7
According to him, we could end up with negative HP......
Lets use your brilliant 10HP motor and say that there is a set 20HP loss through the drive line. How many HP do we have now?
Obviosly there is going to be a certain HP required to move the drive train, but YOUR LOSS all depends on much HP you are pushing through it.
Obviosly there is going to be a certain HP required to move the drive train, but YOUR LOSS all depends on much HP you are pushing through it.
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03-13-2002, 08:58 AM
#10
Simple.
"Drive line loss" should really be termed "drive line efficiency(inefficiency)"
And efficiency is the ratio of output/input. Having a ratio (a percent) is inherent with how drive line loss is quantified.
The real question you should be asking is whether driveline loss is dynamic or static and/or whether it's linear through-out the whole RPM range of the engine. Also when does the driveline loss approach SS?
So I think to simplify things, drive line loss is assumed to be linear and taken at operating temperature in the dynamic state. Hence the simple ratio.
And efficiency is the ratio of output/input. Having a ratio (a percent) is inherent with how drive line loss is quantified.
The real question you should be asking is whether driveline loss is dynamic or static and/or whether it's linear through-out the whole RPM range of the engine. Also when does the driveline loss approach SS?
So I think to simplify things, drive line loss is assumed to be linear and taken at operating temperature in the dynamic state. Hence the simple ratio.