Lets say you had a motor that had been on a engine dyno that had 500 horsepower and 500 foot pounds of torque for example. That same motor was installed in a 4x4 truck that was equiped with a 5 speed manual transmission. How much power does it kill before it gets to the rear wheels? How much more does it kill being a 4x4 than it would if it was a 4x2? Same goes for the 5 speed. I have heard different numbers from some of the guys I work with, but really would like some replies from you guys here. Any help will be appreciated.

 

typical driveline "rob" is 10-30%. a five speed actually steals less than an automatic because its more of a direct link between engine and drive train and less rotating mass.

 

Ditto. All other things being equal, you will lose less power through a manual than you will through an automatic. However, the actual amount will vary from transmission to transmission, as wella s with the individual operating conditions of that trans.

The same goes for the different drivetrain configurations. The 4wd system by itself is, for the most part, just dead-weight when in 2wd. When in 4wd, with the additional rotating mass, there will be some drag, but again, the actual amount will vary based on the gearing, lube, and temp of everything involved. There is no right answer.

10-30% through the drivetrain is a wide range, but there's really not much more accurate way to estimate it. You could always dyno the motor to get the power at the crank, then dyno the truck and measure the RWHP. Do a couple quick calculations, and you'll find that the drivetrain loss will generally be between 10 and 30%.

-Joe

 

Thanks for the replies. I am trying to get a indication of how much power the new motor that is going in my truck is actually pushing, since truck will be on chassis dyno only. This will help a great deal in doing that .

 

Hi.

Some more good reading ... you'll find the actual losses are huge for automatics.

https://www.f150online.com/forums/sh...56&postcount=2

Search for lots more on this subject.

Cheers
Bubba

 

Thanks MGDfan . It don't get any better than that

 

Power to the rear wheels is the only thing that matters anyways...those are pretty much the only numbers you'll find on the site to compare to, so it'll give you a good indication of how much power you make compared to others.

FWIW there's a dyno sticky in the supercharger forum, all measurements taken at the rear wheels