A good day at the dyno...

[tpepmeie]

Originally Posted by Hib Halverson

Actually, your engine is making more than 558. The parsitic loss number for C4 manual powertrains which GM gave me an number of years ago was 18%. If you use that, you're making 578, but, either way that's impressive from a 350 and that's the good news.

Hib,
My personal experience doesn't back up the fixed 18% driveline loss. I believe that may have been relevant for a 300hp LT-1, with a 55 hp loss through the driveline (18%).

In my experience, a 703 BHP (STP corrected), 669 bhp (SAE 1367) engine horsepower made 638 SAE 1367 rwhp on a dynojet.

The engine dyno numbers were "green", the engine was more broken in by the time of the chassis dyno.

The chassis dyno was confirmed and consistent over three sessions and two different dynojets.

I was also surprised by the losses, given the urban legends about 15 or 18% and so on.

YMMV,
Todd