I always approach math with a bit of skepticism when used to guess HP because there are too many variables to put into the model, several of which are not even known and are also disputed by even the most intelligent and technically minded experts in the field. That being said, it's Sunday morning and I'm not done with my coffee yet, so here goes....
In what is probably the most perfect MN12 drag race recorded, Kurt K and I ran against each other to a finish of around .003sec if I recall correctly. We both ran near perfect 12.64's @ 108mph, literally door to door all the way down the track. Kurts car was a CMRE S2 engine with an Sport with 10% OD (I believe) whereas I had a similarly built but non CMRE engine with also an Sport and 10% OD. So we had very similar engines, but his car was a non-locking AOD and mine was a 5spd. We launched about the same with me coming out a fender ahead and him then pulling that back plus a touch more on the 1-2 shift after which time I inched on him until we crossed the line together at the same MPH.
Kurts car weighed about 3950 with driver, mine was about 3750 with driver. Both cars were dyno'd prior to the race, Kurt's at 310rwhp, mine at 345rwhp. Different dyno's, different days, but mine was dynoed several times at different dyno's and repeated the #'s. I think Kurt's did as well.
Again, this is about as close as you'll get to an objective comparison.
So if we do the math, interestingly enough, my 12.64 = 343rwhp - again, by the math only. Kurt's 12.64= 313rwhp (we use a different formula for autos than we do for 5spds). This is a predictive formula, not a physical one, which is why the two are different. This formula has been tested in real world applications many of times. Evidence suggestes that it takes less measured rwhp in an auto to run a certain time than it does in a manual transmission. The theory is complicated, the model is very simple.
Anyway, so if we take the calculated #'s and look for a theoretical flywheel HP number, we find that 343 x 1.15 = 395fwhp and 313 x 1.25 = 391fwhp. In my opinion, with properly built engines the biggest factor regulating power is the blower and blower rpm, so considering that we were using the same blower with the same drive ratio, and very similarly built motors, I feel is is rational to conclude that actual power output at the engine was probably very close to the same on both cars. The fact that Kurt's theoretical # is lower than mine makes me think that 1.25 might not be quite enough. If you change that to 1.28, which by the way is a number I have heard engineers report for the 4R70W (AOD should be very similar), then Kurt's number comes out to an even 400fwhp. When you consider that 400hp is the number that Coy Miller used to advertise for his S2 motors (and this was based on the only actual dyno testing I have ever heard of on an actual SC engine) then I think you have to consider this model to be relatively accurate.
So there you go. Where's my coffee? lol
