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RWHP conversion to engine HP?
Quick question:
I know mustangs generally have a 15% parasitic loss from the crank to the wheel. A Z06 is probably more efficient. What is the equation to figure out engine HP in a C6 Z06. My Z06 has 570 RWHP How much is that at the crank? |
My guess is 12% to 14% depending o what has been done to the car.
Jim |
Here's what I was told by Mike at Vengeance Racing in Cumming, GA...
Mike from Vengeance said the relationship of HP at the fly is a ratio of 1.16 : 1.00... they dyno only gave me 483 RWHP, so extrapolating back we get to 560hp at the fly (which is only an estimate). |
Originally Posted by Painrace
(Post 1572297785)
My guess is 12% to 14% depending o what has been done to the car.
Jim |
Originally Posted by Capt_South_USMC
(Post 1572297698)
Quick question:
I know mustangs generally have a 15% parasitic loss from the crank to the wheel. A Z06 is probably more efficient. What is the equation to figure out engine HP in a C6 Z06. My Z06 has 570 RWHP How much is that at the crank? The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on. I'd be proud to say 570 RWHP, that's a damn good number that puts you in a very limited class of cars in the US.:thumbs: |
Don't argue with this man (aka. glass slipper), he knows what he's talking about and has a TON of experience with measuring HP...and please don't ask how I happen to know this :eek:
Cheers, Paul. |
Originally Posted by glass slipper
(Post 1572298316)
Three posts and you already have four "equations" or numbers. Obviously there's a problem and the problem is there is no one number you can use because it's not a linear relationship. The equation for HP loss is HP=Ax˛+Bx+C where x is the engine HP, A is exponential losses, B is linear losses, and C is constant losses. Exponential losses are things like inertia (on a pure inertia chassis dyno only), linear losses are things like friction at the gears, constant losses are things like gear churn or oil windage in the transmission/differential, tires, and seals (in other words, they're independent of engine HP). Most losses are constant losses so you'll be closest to FWHP if you add a constant plus a fudge factor if you have a known loss from a specific drivetrain. For Z06s, stock LS7s with 505 HP (SAE certified) have ~55 HP loss through the drivetrain. That puts you at 625 HP. If your peak HP RPM is higher than stock, add another 5 HP. Add another 5 HP for additional loss through the differential gears and that puts you at ~635 FWHP. There is no HP loss to gears in the transmission because there are no gears for 4th gear, it's a straight through power flow where the input and output shafts are "locked" together. Of course I'm assuming the dyno run was done in 4th and your tires were properly inflated. Large variations from SAE atomspheric and engine conditions will throw the readings off significantly also. In other words, if you dyno in very cold temps, the computer runs more timing than during SAE tests so the engine makes more power and the 505 HP starting point is no longer valid. Correction factors greater than 7% are not allowed due to large errors induced in the correction formulas.
The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on. I'd be proud to say 570 RWHP, that's a damn good number that puts you in a very limited class of cars in the US.:thumbs: |
Originally Posted by Capt_South_USMC
(Post 1572297985)
mods to the car include a cam, CAI, headers and x-pipe, tune. None of which I believe would increase parasitic loss.
As I remember my car lost about 65 HP from the engine dyno to the chassis dyno. My car has a lighter clutch and the RPM upgrades. This supports what glass slipper says above. In road racing throttle response is also very important and a dyno does not measure that. Jim |
Originally Posted by glass slipper
(Post 1572298316)
For Z06s, stock LS7s with 505 HP (SAE certified) have ~55 HP loss through the drivetrain. That puts you at 625 HP.
Originally Posted by glass slipper
(Post 1572298316)
The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on.
This should be a sticky. Glass Slipper, you are my new best friend. Finally, somebody who gets it! IF YOU SPEED-READ THIS THREAD, ALL YOU REALLY NEED TO READ IS THE QUOTE ABOVE IN BOLD |
If my memory is right I lost 10.79734%! ;)
Jim |
Bravo! glassslipper that is the best write up on HP loss I've seen, makes good sense too!
I never bought into the 15% static number as a loose. I know its commonly accepted in the mustang world, I've never accepted it. |
Originally Posted by glass slipper
(Post 1572298316)
Three posts and you already have four "equations" or numbers. Obviously there's a problem and the problem is there is no one number you can use because it's not a linear relationship. The equation for HP loss is HP=Ax˛+Bx+C where x is the engine HP, A is exponential losses, B is linear losses, and C is constant losses. Exponential losses are things like inertia (on a pure inertia chassis dyno only), linear losses are things like friction at the gears, constant losses are things like gear churn or oil windage in the transmission/differential, tires, and seals (in other words, they're independent of engine HP). Most losses are constant losses so you'll be closest to FWHP if you add a constant plus a fudge factor if you have a known loss from a specific drivetrain. For Z06s, stock LS7s with 505 HP (SAE certified) have ~55 HP loss through the drivetrain. That puts you at 625 HP. If your peak HP RPM is higher than stock, add another 5 HP. Add another 5 HP for additional loss through the differential gears and that puts you at ~635 FWHP. There is no HP loss to gears in the transmission because there are no gears for 4th gear, it's a straight through power flow where the input and output shafts are "locked" together. Of course I'm assuming the dyno run was done in 4th and your tires were properly inflated. Large variations from SAE atomspheric and engine conditions will throw the readings off significantly also. In other words, if you dyno in very cold temps, the computer runs more timing than during SAE tests so the engine makes more power and the 505 HP starting point is no longer valid. Correction factors greater than 7% are not allowed due to large errors induced in the correction formulas.
The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on. I'd be proud to say 570 RWHP, that's a damn good number that puts you in a very limited class of cars in the US.:thumbs: Stephen :cheers: |
:iagree::iagree:
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Originally Posted by glass slipper
(Post 1572298316)
Three posts and you already have four "equations" or numbers. Obviously there's a problem and the problem is there is no one number you can use because it's not a linear relationship. The equation for HP loss is HP=Ax˛+Bx+C where x is the engine HP, A is exponential losses, B is linear losses, and C is constant losses. Exponential losses are things like inertia (on a pure inertia chassis dyno only), linear losses are things like friction at the gears, constant losses are things like gear churn or oil windage in the transmission/differential, tires, and seals (in other words, they're independent of engine HP). Most losses are constant losses so you'll be closest to FWHP if you add a constant plus a fudge factor if you have a known loss from a specific drivetrain. For Z06s, stock LS7s with 505 HP (SAE certified) have ~55 HP loss through the drivetrain. That puts you at 625 HP. If your peak HP RPM is higher than stock, add another 5 HP. Add another 5 HP for additional loss through the differential gears and that puts you at ~635 FWHP. There is no HP loss to gears in the transmission because there are no gears for 4th gear, it's a straight through power flow where the input and output shafts are "locked" together. Of course I'm assuming the dyno run was done in 4th and your tires were properly inflated. Large variations from SAE atomspheric and engine conditions will throw the readings off significantly also. In other words, if you dyno in very cold temps, the computer runs more timing than during SAE tests so the engine makes more power and the 505 HP starting point is no longer valid. Correction factors greater than 7% are not allowed due to large errors induced in the correction formulas.
The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on. I'd be proud to say 570 RWHP, that's a damn good number that puts you in a very limited class of cars in the US.:thumbs: |
Originally Posted by Katech_Jason
(Post 1572299597)
I had to read this a few times before I understood what you're getting at. You're saying his 570rwhp car plus 55hp estimated drivetrain loss equals 625hp.
This should be a sticky. Glass Slipper, you are my new best friend. Finally, somebody who gets it! IF YOU SPEED-READ THIS THREAD, ALL YOU REALLY NEED TO READ IS THE QUOTE ABOVE IN BOLD It's been said before but people want to hear what they want to hear. Losses being quadratic is nothing new. My 600 rwhp is probably getting close to somehwere around 650 BHP is my estimate. |
Wow . Glass , great post . Everyday I learn something form this forum . Thank you .:flag:
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General conversion for C6s is approx. 12-13%.
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Originally Posted by glass slipper
(Post 1572298316)
Three posts and you already have four "equations" or numbers. Obviously there's a problem and the problem is there is no one number you can use because it's not a linear relationship. The equation for HP loss is HP=Ax˛+Bx+C where x is the engine HP, A is exponential losses, B is linear losses, and C is constant losses. Exponential losses are things like inertia (on a pure inertia chassis dyno only), linear losses are things like friction at the gears, constant losses are things like gear churn or oil windage in the transmission/differential, tires, and seals (in other words, they're independent of engine HP). Most losses are constant losses so you'll be closest to FWHP if you add a constant plus a fudge factor if you have a known loss from a specific drivetrain. For Z06s, stock LS7s with 505 HP (SAE certified) have ~55 HP loss through the drivetrain. That puts you at 625 HP. If your peak HP RPM is higher than stock, add another 5 HP. Add another 5 HP for additional loss through the differential gears and that puts you at ~635 FWHP. There is no HP loss to gears in the transmission because there are no gears for 4th gear, it's a straight through power flow where the input and output shafts are "locked" together. Of course I'm assuming the dyno run was done in 4th and your tires were properly inflated. Large variations from SAE atomspheric and engine conditions will throw the readings off significantly also. In other words, if you dyno in very cold temps, the computer runs more timing than during SAE tests so the engine makes more power and the 505 HP starting point is no longer valid. Correction factors greater than 7% are not allowed due to large errors induced in the correction formulas.
The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on. I'd be proud to say 570 RWHP, that's a damn good number that puts you in a very limited class of cars in the US.:thumbs: My stock '06 Z06 has dynoed 471rwhp SAE.... I realize my car is no freak..... it was a good day on that dyno is all! Also my car traps 126 in pretty good air... just like all the other well driven stock Zs..... freak it is not. |
Originally Posted by glass slipper
(Post 1572298316)
Three posts and you already have four "equations" or numbers. Obviously there's a problem and the problem is there is no one number you can use because it's not a linear relationship. The equation for HP loss is HP=Ax˛+Bx+C where x is the engine HP, A is exponential losses, B is linear losses, and C is constant losses. Exponential losses are things like inertia (on a pure inertia chassis dyno only), linear losses are things like friction at the gears, constant losses are things like gear churn or oil windage in the transmission/differential, tires, and seals (in other words, they're independent of engine HP). Most losses are constant losses so you'll be closest to FWHP if you add a constant plus a fudge factor if you have a known loss from a specific drivetrain. For Z06s, stock LS7s with 505 HP (SAE certified) have ~55 HP loss through the drivetrain. That puts you at 625 HP. If your peak HP RPM is higher than stock, add another 5 HP. Add another 5 HP for additional loss through the differential gears and that puts you at ~635 FWHP. There is no HP loss to gears in the transmission because there are no gears for 4th gear, it's a straight through power flow where the input and output shafts are "locked" together. Of course I'm assuming the dyno run was done in 4th and your tires were properly inflated. Large variations from SAE atomspheric and engine conditions will throw the readings off significantly also. In other words, if you dyno in very cold temps, the computer runs more timing than during SAE tests so the engine makes more power and the 505 HP starting point is no longer valid. Correction factors greater than 7% are not allowed due to large errors induced in the correction formulas.
The bottom line is you'll never know what your FWHP number is unless you remove the engine and test it IAW SAE procedures. Most people wanting to back calculate FWHP are looking for a large number to stroke their ego and use 15-16% while a stock Z06 is actually closer to 10% and that number goes down as you add HP if you wanted to go by percentage. But that means it's a moving target. Pick whatever number you want if you're looking to stroke your ego. The only thing you really know is you have 570 RWHP, and even then that's only on that particular dyno on that particular day with that particular tire pressure....and on and on. I'd be proud to say 570 RWHP, that's a damn good number that puts you in a very limited class of cars in the US.:thumbs: |
Thanks for all the great info, I just had my corvette dyno performed last week and I had 365 RWHP and I am happy.
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