I know this is a dumb question I just need to know for somthing. So if someone modifies there car with lets say a ecu upgrade and get 30 whp what is that at the crank? Is 50 Hp fair or less?

 

you dont gain at the flywheel you lose hp from whp to the crank. you have it backwards.Cancel that i misunderstood you for a second

 

figure about 10-15% gain for driveline loss

 

close to 50 would be about right

 

On an all wheel drive car the loss is closer to 20% which would give you about 36 hp at the crank.

 

+1

 

Is only 36 Hp at the flywheel? That suxx

 

That depends on what you're starting with.

What kind of car, a WRX? I'd say 36hp is a significant amount if nothing else is being modified, like the exhaust system.

 

I would also say it is closer to 20% on AWD. My friend dyno'd his stock evo 8 and got around 220whp.

 

It's typically 20-25% drivetrain loss from BHP to WHP on an all wheel drive car.

Using a 20% loss figure, divide 30 by .8 [1 - .2 = .8] and you get: 30/.8 = 37.5 BHP. Assuming 25% drivetrain loss you get: 30/.75 = 40 BHP.

36 isn't accurate because you got that number from multiplying 30 x 1.20 (120%). That's not the correct way to calculate BHP from WHP.

WHP / (1 - (DriveTrainLoss%)/100) = BHP.

And of course, your BHP is just an estimate which completely depends on your drivetrain loss figure.

 

Who cares what you got at the crank when what is at the wheels is what you can actually put down on the road.

And remember that horsepower is NOT the whole picture.

Torque causes acceleration and power is Torque x Angular Velocity, so power tells you at what speed you can apply a certain torque.

The higher the gear ratio the more torque at the wheels, the harder you can accelerate, but the more horsepower you have the faster you can go while applying that torque.

By the way, i think it would be safe to assume a powerloss of at least 30% for all wheel drive cars, especially if your car uses viscous coupling for its differentials, where some power gets stored into the inertia of the fluid.

Did i confuse you yet.

 

my stock 05 evo 8 gsr was dynoed at 265awhp it was at dynojet dyno so it was like only 5% loss compared to stock bhp

 

If you're getting that much power at the wheels, it means your car is putting out a lot more than that. 5% drivetrain loss would be possible if your car had only one or two gears with no differentials and all the other connections between the crank and your wheels.

 

you know people, he was asking about how much 30WHP would equal in BHP...

on topic: 50 sounds about right