Wheel Horse Power vs Actual Horsepower?

[GSR-VR]

I'm not new to the terms flywheel horsepower, brake horse power, and wheel horsepower. But then a person at a local meet throws "actual" horsepower out there. I ask him to elaborate on the term and he said its, "drivetrain looses and atmosphere looses." ???

I was under the impression when someone says wheel horsepower that means (regardless of altitude) what the car made to the wheels.

Any light shed on this subject would be great.

Thanks!

 

[turbo98eclipse]

Hes referring to the motor itself... not whp

You said he said actual hp, not wheel hp. Actual=motor & wheel/brake=wheel

 

[Breezio69]

The only way to know this number 100000% is to pull the motor and set it up on an engine dyno. It takes a reading from the crank. It is basically a full setup, it has exhaust vents, intake, fuel cell, its hooked up to computers to control the throttle and injectors etc... that is what gives you the reading at the crank, or flywheel.

Anything other than that, you have to take into account drivetrain loss, fwd, rwd, awd. From there it is a guessing game on ACTUAL hp at the crank. A 400 crank hp car could show up as 320 on an awd platform, or 360 on a fwd setup.

These numhers are a guesstimate, I'm sure there are many highly educated guesses or answers in the googlesphere as to how much drivetrain loss is accounted for in both platforms of a dsm... but in the end, they are still just highly educated guesses without hooking up to an engine dyno.

For what its worth, almost ALL car manufacturers give you a crank hp number on the sales slip. They don't take into account any drivetrain loss or measure whp. A 225hp run of the mill stock wrx is expected to have around a 25% drivetrain loss. Thats close to fifty ponies from the brochure you fell in love with, whilst sitting eager to get your $25k loan. Or take the rx8 mis advertising 6-7 years ago, where they appologized to all their customers for advertising way over the real hp numbers.

So basically, the guy you were talking to went ot a dyno... if at all... and either guessed his actual numbers on his own, or had "corrected" numbers from a dyno. Which can be accurate, aren't 100%. The same setup on two cars with two different tunes could yield drastically different numbers.

 

[cliffkemp]

The only way to know this number 100000% is to pull the motor and set it up on an engine dyno. It takes a reading from the crank. It is basically a full setup, it has exhaust vents, intake, fuel cell, its hooked up to computers to control the throttle and injectors etc... that is what gives you the reading at the crank, or flywheel.

Anything other than that, you have to take into account drivetrain loss, fwd, rwd, awd. From there it is a guessing game on ACTUAL hp at the crank. A 400 crank hp car could show up as 320 on an awd platform, or 360 on a fwd setup.

These numhers are a guesstimate, I'm sure there are many highly educated guesses or answers in the googlesphere as to how much drivetrain loss is accounted for in both platforms of a dsm... but in the end, they are still just highly educated guesses without hooking up to an engine dyno.

For what its worth, almost ALL car manufacturers give you a crank hp number on the sales slip. They don't take into account any drivetrain loss or measure whp. A 225hp run of the mill stock wrx is expected to have around a 25% drivetrain loss. Thats close to fifty ponies from the brochure you fell in love with, whilst sitting eager to get your $25k loan. Or take the rx8 mis advertising 6-7 years ago, where they appologized to all their customers for advertising way over the real hp numbers.

I have an rx-8 and do agree with you on that to an extent. I did manage to get mine to 200 whp with a few bolt-ons. The HP that matters is WHP. Funny how most makers use crank hp. What you say is true though. As a car sees more and more age and parts start to ware out, the whp will drop depending on bearings and things of that nature.

After reading most of the major magazines for the last 25 years, most cars put down the most hp at or around 40k miles or so. After around 75k, many cars start to get slower.