Originally Posted by
Greg Amy
Scratch that whole paragraph from above; I'm even confusing myself here...
18% is actually a DISADVANTAGE within the IT process for RWD. What you (Travis, and all other RWD'ers) want is to have everyone at 15%, that way when ACTUAL whp is back-calculated to chp, the numbers - and thus the percentage above Process - come out lower.
Example: 140 stock crank hp (chp) car. Standard process says the car "should" get 140*1.25 = 175 chp after IT mods. Car is dyno'd on a Dynapack; actual measured whp is 150.
Using 15%, calculated chp is 150/0.85= 176.5 = 100.8% of process = no "what we know" adder.
Using 18%, calculated chp is 150/0.82 = 183 = 104.5% of process = +5% "what we know" adder.
So, is there actually a difference in drivetrain losses between FWD and RWD? If so, as that percentage-number-used grows the disadvantage (in terms of The Process) for RWD'ers grows. On the other hand, if there truly is a larger disparity than what we're actually using (spnkzss mentions 15/20% for drag racing, another number I've heard tossed around) then the larger the actual disadvantage for FWD cars.
I'll toss in the simplicity bone and contend that there is no significant difference in drivetrain loss between FWD and RWD, and thus 15% should be used for all cars in IT.
Did I get it right this time...? - GA
i was going to correct you.....but i'm trying to get work done.
yes, i think you've got it this time. i'd bet donuts to dollars that the 15/20 numbers are no more of an actual calculation with legitmate math and reasoning behind it than the 15/18 POOMA number.
the problem here is that very small discrepancies in our estimates and "data" (3% driveline loss difference, 5whp) result in very real and significant changes to the minimum weight (100lbs).
i don't like it, and i'm afraid these beliefs rooted in just about nothing but time will point the ITAC to a conclusion at the detriment to any RWD car somebody feels needs a second look.
Travis Nordwald
1996 ITA Miata
KC Region
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