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The BarTender
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Discussion Starter · #1 ·
I have confused myself all to hell with this and now I ask for your help. I am trying to figure out what kind of horsepower my car is making at the flywheel. I am making 496 at the rear wheels now. How do I convert this mathmatically to figure Flywheel numbers? Thanks in advance for any help.:D

Razor.
 

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There are lots of different percentages people like to use. Some even say a fixed number.

My personal opinion is that a modern car with a modern gear box will use 11-13%. Straight axle and lighter duty rans cars (like T-45's and T-5's) cars on the lower side, cars with IRS and TKO's and T-56's on the higher side.

I've seen posts on the viper boards about engines dyno'ed on engine dyno's vs in the car oon the chassis dyno. they say around 12%. the have a T-56 and IRS.

Ford's published numbers for chassis results on the 99 Cobras said they should have at least 272 rwhp. That is 15%. I think they were covering themselves a little.

Anyway divide the chassis number by 1- the percentage.

For 15% 272/.85=320
For a car at 12% 465/.88=528

JT
 
G

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Yep....thats about right for the conversion of todays crank horsepower ratings from rear wheel....but if you want to see about how much Horsepower your car would have been rated in the 1960's...then it would be in the 25% more HP. area.

So for 1960's ratings...the rear wheel horse of todays 400 HP would be about 500 HP in those early day ratings. So our Cobra's are pretty stout.

The newer ratings have all the accessories on the motor...back then...it was just the motor setup to optimum performance ...and still the factories rated above. Thats until the insurance companies came into play...then they started to downplay it abit.
 

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The BarTender
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1,651 Posts
Discussion Starter · #4 ·
Thanks for the reply fellas. I have now confirmed that my car wich makes 496 at the wheels, Turns 583.5 at the flywheel. :D

15% 496/.85 = 583.5 Horsepower.

Woot Woot!!:shocked

Razor.
 
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