Originally Posted by tom2112
Hey Franc, not to bust your chops or anything, but where'd you come up with those numbers?
If you're car dyno'd at 193.5 whp then your crank hp would be approx. 236, not 290. Wheel horse power numbers are roughly 82% of crank horse power numbers (which accounts for 18% drive train loss).
The other numbers you posted don't make sense to me.
The 215 and 229 numbers are crank hp numbers published by the manufacturer - not rear wheel hp numbers. If they were to put those cars on a dyno, they would read roughly 18% less for rear-wheel horse power numbers, such as 176 and 188. Of course, every dyno is a little different, so allow a couple % variation, but you get my point.
So I don't understand your reference to 215 pushing 300.
I went back and ran the numbers as well. Ignoring the SLK numbers and simply sticking to our "alleged" 215HP, I compared baseline crank HP with his measured baseline wheel HP.
154RWHP / 215Crank-HP = .71 x 100 = 71%
That's a whopping 29% parasitic drivetrain loss...
Is that even possible?!?
Based on 18% losses, which is industry average for a manual, one
should be seeing ~175 RWHP from the factory, right?
Even applying that catastrophic correction figure to the 'post-tune' numbers of 193.5 RWHP, I came up with:
193.5 x 1.29 (to correct for previously calculated drivetrain losses of 29%) = grand total of
249.6 Crank HP...
249.6 - 215 (factory claim) =
net gain of 34.6 HP.... Not shabby, but not even close to 280.
That's my math... if anyone disagrees, I'm open for suggestions.