MarineBlue03GMC

I am trying to figure out the flywheel to wheel hp/tq loss percentage on an automatic 5.3L truck. I have heard that the percentage is either 20% or 23%.

Does anyone have any opinions on this matter?

If EITHER of these figures are correct it would seem that many trucks specifically a few 5.3 03's on this forum are making over 300+ hp STOCK at the flywheel! Thats 15+ hp over what GM is rating the trucks from the factory. Basically I am having a hard time believing some of the 5.3 03 stock dyno numbers.

BigJ

I thought drive train loss was around 10-12% on our trucks. I'm sure someone will know for sure, but I'm almost positive it's 10-12%.
My 01 (Rated @ 285hp, 325tq @ the flywheel) dynoed at 256hp/297tq. I had the K&N FIPK and 2 flows at the time. Thats around 11% roughly.

GREGGO

iTrader: (2)

It averages 20-21% in most cases for these trucks.

408 Stepside 01

Do you guys know what the f-body six speed %. I have a couple of buddies that have six speeds. There cars just absolutely crap on automatics with the same mods.

00scsb325

I believe it is around 20% also. I only dynoed 240.4 rwhp and 283.0 rwtq before the cam install. That was on the dyno jet though, I hear that all dyno's read differently.

427ZO6

On a six speed Camaro of Firebird the loss, RWHP vs flywheel HP is 15%. With an automatic the loss 20%. Similar figures would hold true for PU as well.

Flem

there is a lot of conflicting info out there on HP #'s there are two different types of chassis dynos Eddy current (Mustang) and inertial (dynojet). the Dynojet is good for lighter vehicles but, the Inertials can be tricked w/ stall converters to read higher torque readings. The mustangs read true toque through electrical current. If you look through posts there seems to be a concensus that the Mustangs read 9-11% lower than Dynojets but have a better correlation (more accurate) to actual 1/4mile runs. the hp/trq. seems to fall this way manual trans. 13-15% - automatic 16-20% 4wd-automatic 20-23% AWD is in the 19-23% area but its hard to find 4wd chassis dynos,let alone ones large enough to fit fullsize trucks.

Flem

Oh in addition the 5.3's are commonly making 300+ HP from the factory, thats why the ratings will change next year to 305HP

MarineBlue03GMC

Well thanks for all the info everyone. I guess there is no definite percentage especially since some engines just seem to make more power from the factory.

So Flem where did you hear about the 305hp rating on the 5.3s for next year? Any actual GM literature on this?