RWHP Conversion Factors

[2k2TahoeSS]

Is there some sort of formula i can use to figure out about how much RWHP i have, based on what my HP is?  Thanks.

 

Ben

[SilveradoWV]

From various results I have heard, I dont think there is an actuall conversion. It seems like it doesnt matter if a vehicle has the same mods or not, their RWHP is different no matter what. For some reason I am thinkin on average people lose about 40+ hp when measuring it at the rear.

[SnakeEyeSS]

I think 20% is about whats lost, if I remember correctly, to give you an est.

[Roofer]

I have always heard 17% power loss through an auto  drivetrain in a GM truck. The Allisson may be a bit different though. Not sure if this is correct, but I think it is real close.

[sivart]

There is no conversion table. There are too many variances tho HP loss and Gain to the rear wheels. Pulleys, Tranny, Rear diff ratio. I have always heard to go by 20% and it has always fallen pretty close to actual.

[CMNTMXR81]

It's simply a factor.  It ranges from 15% - 20% less at the rear wheels.  Usually manuals are closer to the 15% mark and automatic's closer to the 20%.

 

For instance, a stock Vortec 5300 with a 4L60E is "rated" at 285hp.  285*.80 (1.0-.20 for auto) should net you in the vicinity of 228 rear wheel hp.  Plus or minus a few.  But that is the area it should be.

 

Of course if you throw it on a chassis dyno and get 250 rear wheel HP, you like the LS1 folk know GM per chance has slightly under rated the 5.3