Transaxle Tic-Tic! Need Help Please!

[Cattrax]

Michael,
Lots of reasons for 21% drivetrain loss. Peak torque is at a much higher RPM on the engine dyno chart. Since I am sure the cam and heads were not changed, I am guessing they used a different exhaust or intake system for testing on the stand. Also you mentioned tuning in the car thus implying that the ECU was not pulled and tuned on the stand. Intake and/or exhaust change could easily up the normal 15%+- loss to 21%. Other factors could be cold transmission lube, tire pressure, brake pads not pushed back, and sweep rate. Changing the sweep rate will change indicated HP even when on the same dyno on back to back runs. Basically it takes some HP to accelerate the flywheel and other internal components. If you try to let the engine increase RPM at a high rate, say 1000 rpm/sec, it uses much of it's power just to accelerate itself. If you want to brag, just have them run a "step" test where the engine is held at each point for a second or so. The mags used to do that to show high numbers. 200 rpm/sec is a fairly typical sweep rate. Use lower for glory runs, higher for ease on the engine.
Torque and HP curves look great! Pulls strong to 6500rpm and beyond. It should be fun to drive.
Ken

[RumRunner]

Michael,
Lots of reasons for 21% drivetrain loss. Peak torque is at a much higher RPM on the engine dyno chart. Since I am sure the cam and heads were not changed, I am guessing they used a different exhaust or intake system for testing on the stand. Also you mentioned tuning in the car thus implying that the ECU was not pulled and tuned on the stand. Intake and/or exhaust change could easily up the normal 15%+- loss to 21%. Other factors could be cold transmission lube, tire pressure, brake pads not pushed back, and sweep rate. Changing the sweep rate will change indicated HP even when on the same dyno on back to back runs. Basically it takes some HP to accelerate the flywheel and other internal components. If you try to let the engine increase RPM at a high rate, say 1000 rpm/sec, it uses much of it's power just to accelerate itself. If you want to brag, just have them run a "step" test where the engine is held at each point for a second or so. The mags used to do that to show high numbers. 200 rpm/sec is a fairly typical sweep rate. Use lower for glory runs, higher for ease on the engine.
Torque and HP curves look great! Pulls strong to 6500rpm and beyond. It should be fun to drive.
Ken

Excellent information! Thanks,

-Michael