Today we dyno'd the motor on my RSR Clone. Auto Associates has a chassis dyno that hooks up with the rear hubs for better repeatability in the measurements.
As a reminder the motor is based on a a 3.0 SC case with the following:
Twin plug heads and dizzy
RSR spec twin plug heads
10.5:1 Mahle RSR pistons & Cylinders (CR verified by build measurements)
GE-60 style cams from Camgrinder
Turbo oil pump
46 mm PMO's
RSR headers
RSR style ralley muffler
Single MSD driving two coils
I built it my self using Wayne's book as my bible and the guys at Auto Associates as my consultants.
We dyno'd the motor both with the ralley muffler caps off and then on.
HP results
HP peaked at 250 at 7500 RPM's with the caps off. There are three runs clustered together showing about the same results with the caps off. Accounting for 15% driveline losses gives about 285 HP from the engine. The lower light blue curve is the one run we did with the muffler caps on showing about a 20 HP drop for the muffler.
Torque
Torque is between 165 and 180 ft-lbs from 4000 to 7000 RPM. Accounting for driveline loss equates to 190-207 ft-lbs from the engine. The muffler causes a loss of 20 ft-lbs across the rev range consistent with the 20 HP loss.
A/F Ratio
AFR runs at about 13-13.5 across the rev range. The muffler leans out the mixture and causes it to run between 11 and 12.
Overall I'm very satisfied with the results and would love to hear your comments. Scott at Auto Associates has built several motors to this spec and he predicted the HP dot-on.
The dirveability is great. It is very tractable from 1000 RPM idle up to 4000 RPM. At that point it begins to really kick in. I cant say thay I've really explored the upper limits just yet. Next up will be some acceleration trials and then a drivers ed at Lime Rock in Nov.