explain the hp ratings please

[steve1ph]

could some one please explain the hp rating?

 

[Mad-Mic]

what do you mean the horse power rating?

fly wheel or rear wheel?

 

[92ghost]

Your actually asking a very general question. Can you be more specific.

Wayne

 

[Tom73]

could some one please explain the hp rating?

Are you asking what HP is or how the HP rating is determined?

tom...

 

[steve1ph]

ok. what im wanting to know is the diff between "rwhp" and "at the fly wheel" and which the local dealership post on the window sticker and why.

 

[92ghost]

I will try my best to explain. Rear wheel Horse Power or RWHP is roughly 15%-20% less power than the Fly Wheel Horse Power rating. This is due to drive train loss such as Automatic/Manual transmissions, gears, weight of the tires and wheels etc. Fly Wheel Horse power is what the engine will do on a dyno out of the car but with the Air Conditioner, Alternator, Power Steering, Power Break pumps etc. Way back in 1972 the Automotive industry switched from Gross Horse Power to NEt Horse Power. This meant that prior to 72' the HP rating was from the engine without any accessories such as Alternator, Power Steering, power breaks etc. This added up to about 50 HP. All said and told, RWHP says it all, no mater what your flywheel HP Gross/Net is the proof is what gets to the ground.

Hope I explained this correctly.

Wayne

 

[steve1ph]

you did. the rubber, mustang, trans am, camero ss, ls corvette left behind is what im after.

 

[92ghost]

Dealer Window stickers will show Fly Wheel HP through the accessories. This is universal throughout the Auto industry to keep apples to apples. But, it's not uncommon for a manufacturer to UNDER RATE the true output of an engine. I think the LT4 comes to mind as an Under Rated performer.

 

[Tom73]

Rear wheel HP is a speed shop/hot rod term. Factories never used it. They only rate cars at the flywheel using an engine dyno. As mentioned above, prior to '72 the flywheel HP was without any accessories or power robbing equipment installed. For '72 and later the HP was determined with ALL standard equipment in place.

RWHP is a useless number as there are too many variables ranging from the type/brand of chassis dyno to the conditions the test were run under. The only way to have viable RWHP numbers is to run all the tests on the same dyno and by the same operator.

tom...