translation whp to engine hp

[Mike_GSX]

Hello,

I hear a lot of people talk about whp.
Here in europe we only talk about engine hp.

Can someone tell me what the translation is?


Lets say 350whp is 437.5 engine hp on a GSX (20% drivetrain loss to whp?)
is 388.0 engine hp on a GST (10% drivetrain loss to whp?)

am i correct?

Thanks a lot

Mike_GSX

 

[coreyr]

it doesnt work like that, a drivetrain only takes X amount of horsepower to turn it, the loss does not go up with horsepower. for example you have a car that comes stock with 250 flywheel horsepower. lets say it absorbs 50 HP throuight the drivetrain. now you up the crank horsepower to 500, it doesnt take any more than that initial 50HP to turn the drivetrain.

 

[Mike_GSX]

Hi coreyr,

this one I don't get.

If my 95 GSX has 300whp how many flywheel hp does it have?
and when it has 350whp how many would that be?

Maybe I get it right. Stock is 210 flywheel hp. drivetrainloss is 20%, that means whp sould be 170whp (loss of 40flywheel hp).

so for 300whp that would be 340 (40) on the flywheel and for 350 that would be 390?


Sorry, I'm real confused about that.

thanks

Mike_GSX

 

[DSMunknown]

Hi coreyr,

this one I don't get.

If my 95 GSX has 300whp how many flywheel hp does it have?
and when it has 350whp how many would that be?

Maybe I get it right. Stock is 210 flywheel hp. drivetrainloss is 20%, that means whp sould be 170whp (loss of 40flywheel hp).

so for 300whp that would be 340 (40) on the flywheel and for 350 that would be 390?


Sorry, I'm real confused about that.

thanks

Mike_GSX

The only way you can tell how much power is being lost through the drivetrain is by taking the engine out and putting it on an engine dyno. Get some accurate readings, and then reinstall the engine. Next, take the car to a local chassis dyno shop and have the car tested.

Subtract this number (whp) from the numbers you saw with the engine dyno (bhp). This will show you how much power is being lost through the drivetrain.

Guessing is never the right approach.

Every car is different, even if it's the same model. There are also other factors that are involved. This is why trying to make approximations is ultimately useless.

 

[dave99gst]

Alot of people just guess 10-20% for drivetrain loss. WHP is really the only # that matters.

 

[99gst_racer]

GST's have really close to a 15% drivetrain loss. I'm not sure about GSX's though.

 

[coreyr]

Hi coreyr,

this one I don't get.

If my 95 GSX has 300whp how many flywheel hp does it have?
and when it has 350whp how many would that be?

Maybe I get it right. Stock is 210 flywheel hp. drivetrainloss is 20%, that means whp sould be 170whp (loss of 40flywheel hp).

so for 300whp that would be 340 (40) on the flywheel and for 350 that would be 390?


Sorry, I'm real confused about that.

thanks

Mike_GSX

yes its like that. the 20% drivetrain loss doesnt rise with power increase though. like you said stock horsepower is 210 at the crank, and 170 at the wheels so thats roughly 20%. now if you up your crank horsepower to 400 it doesnt lose 20% of that through the drivetrain it still only loses the initial loss off 40 or whatever it turns out to be.

but like the other guy said every car is different as far as loss. one car manufatured could have tigher clearences on everything which causes more drag and take more horsepower where as something manufactured at a different time could have looser clearences and take less power.