rwhp = how much at the crank?
- Thread starter RikRok
- Start date
V10SpeedLuvr
Enthusiast
Usually you lose 12-15% from the crank to the wheels
KenH
Enthusiast
Most common formula used for Vipers is RWHP/.88 which basically accounts for a 12% driveline loss. 450RWHP would be about 450/.88 = 511HP at the crank.
lankhoss
Enthusiast
Not sure about the GenII's, but it seems as though the SRT's are losing more than 15%. Either that, or the Z06s are losing less.
People said the C5 Z06 lost 13.5% at the drivetrain, and the thicker clutch plates for the C6 should account for a little more loss...so the estimate is about 15%. The Viper and Z06 are rated at almost identical horsepower, but they have been generally dyno'ing 10 - 15rwhp lower than the Z06.
So I'd imagine the SRT-10 is losing anywhere from 16 - 18% through the drivetrain (which is stronger than the Z06, so it makes sense), IF both cars actually have the same crank horsepower.
People said the C5 Z06 lost 13.5% at the drivetrain, and the thicker clutch plates for the C6 should account for a little more loss...so the estimate is about 15%. The Viper and Z06 are rated at almost identical horsepower, but they have been generally dyno'ing 10 - 15rwhp lower than the Z06.
So I'd imagine the SRT-10 is losing anywhere from 16 - 18% through the drivetrain (which is stronger than the Z06, so it makes sense), IF both cars actually have the same crank horsepower.
mjorgensen Woodhouse
Enthusiast
We use a loaded Mustang dyno and have been testing Vipers since day one. We use the same procedures the factory does on the Vipers when they leave the line and we can duplicate the numbers exacly everytime with in 1-2%. The correction we find is needed is 1.25 X rear wheel so 25% loss although each dyno operator may use a different technique. I am not a dyno expert though just know the basics and this is what has given us the most reliable numbers over the years.
Mark Jorgensen
Mark Jorgensen
lankhoss
Enthusiast
1.25X would not mean 25% loss.
If a 400bhp car lost 25% power through the drivetrain, that would mean it had 300rwhp.
If you multiply 300rwhp X 1.25, you get 375hp.
375bhp to 300rwhp is about 17% loss, I think. That sounds pretty close to what I'd think a Viper's drivetrain loss was.
Just curious Mark....what are typical dyno numbers for GenII and SRT Vipers on your dyno?
Thanks in advance!
If a 400bhp car lost 25% power through the drivetrain, that would mean it had 300rwhp.
If you multiply 300rwhp X 1.25, you get 375hp.
375bhp to 300rwhp is about 17% loss, I think. That sounds pretty close to what I'd think a Viper's drivetrain loss was.
Just curious Mark....what are typical dyno numbers for GenII and SRT Vipers on your dyno?
Thanks in advance!
03CobraAV8R
Enthusiast
You can manipulate many things on a Mustang dyno to get any kind of # you want. It doesn't mean it's right. You can't do that on a DynoJet.
Mustang dyno's consistently read ~8-10% lower than Dynojets, and that is a proven fact.
So, you see these low #'s on a MustangDyno, and try to equate it to BHP, of course you're going to be seeing a huge loss through the drivetrain, but that is not correct.
Vipers do NOT lose 25% through the drivetrain, come on, that's more than an average AWD loses (~22%). Sure, that's how much you have to correct for on a Mustang dyno to get what you want to see in BHP, but it is not a correct indication of how much power is actually being lost through the drivetrain.
15% is what the majority of people use for RWD cars, and it seems to be accurate.
Mustang dyno's consistently read ~8-10% lower than Dynojets, and that is a proven fact.
So, you see these low #'s on a MustangDyno, and try to equate it to BHP, of course you're going to be seeing a huge loss through the drivetrain, but that is not correct.
Vipers do NOT lose 25% through the drivetrain, come on, that's more than an average AWD loses (~22%). Sure, that's how much you have to correct for on a Mustang dyno to get what you want to see in BHP, but it is not a correct indication of how much power is actually being lost through the drivetrain.
15% is what the majority of people use for RWD cars, and it seems to be accurate.
Buckeye Viper
Enthusiast
lankhoss
Enthusiast
Sounds pretty accurate. I had heard one time that Vipers tend to lose a little more through the drivetrain than most RWD cars, though.
