Quote:
Originally Posted by CanAutM3
I should have specified 2WD.
10-15% excluding tire losses and inertial impacts? I doubt it would be that much.
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I think that is pretty accurate. Yes, pure LOSSES, not inertial effects. A rough accounting of it for a RWD vehicle would be:
- Auxiliaries: 1% (will be getting lower with EPS and in general with more electrically and mechanically efficient components along with smart shut downs)
- Manual transmission: 3% (both automatics and dual clutch a bit more, but losses are getting smaller with both in each successive generation)
- Differential: 3% (maybe a bit high but the power does have to make a giant 90 degree turn..., good ones like the M4 have a lot of cooling fins too!)
- Hubs and axles: 5%
That's 12%, thus 10-15% excluding tires to cover a range of more and less quality and efficiency of the components. And again, for clarity these are rpm/speed dependent, as such losses clearly are not a fixed percentage across all gears and speeds. The fundamental (simplest) nature of friction is a non-linear force as a function of velocity. I've provided the formula for tire losses and they grow non-linearly with speed, prob. up to about 30 hp for a car like an M4 at top (delimited speed). That's about 7% of 440 hp, quite significant.