Quote:
Originally Posted by oldman
so lets take an example of CF just messing up the math.
Hennessy 750 package: blower, headers, cam, heads, fuel system:
http://hennesseyperformance.com/vehi...arged-upgrade/
Hennessy list it at 751 HP* if you read the star it explains crank HP is 15 to 20% above RWHP... it ain't but at least it is noted. The M6 put out the following numbers 433 RWHP stock and 649 RWHP with their 750 package, bust the calculator out and Hennessy is 15.7% drivetrain loss. So all good (even though I personally think 10 to 12% for an M6). but all good in the since there is no outright deception so far.
Lets look at the actual gain to the wheels: 649 HP - 433 HP = 216 RWHP. That is the true delta and that is what a dyno is for, we all good so far?
What is Hennessy claiming you get from the engine 751 right, and stock was 455 right so that is 296 engine.
We all good? Think so. So how does a near 300 HP engine gain equal just a tad over 200 RWHP????? that my friends is where dyno racing and Unicorn HP come into play.
Please note that Hennessy is near sea level so they can only play so much with Unicorn HP, a shop in Denver with the same car would be quoting like 825 engine HP.
Please check my calculations. If you figure out where all that engine HP went..... then you will understand why I don't like HP correction factors. |
Agreed. Though 649 is 86.4% of 751 so by my math it's a 13.6% powertrain loss for the Henessey 750 on an m6. I understand how you got 15.7%, 751÷749=1.157, though it's not the way I calculate powertrain loss of bhp vs rwhp.
Which is funny because by their own numbers the Camaro's drivetrain wasn't that inefficient judging by their stock numbers of 433rwhp out of a car rated at 455hp, which would be right at a 5% loss rounding up a decibel. Suddenly a car with such an "efficient" powertrain is now losing rwhp at a much higher % of inefficiency lol.
If the car kept the same drivetrain loss % as their stock figures (which I understand wouldn't be the exact same necessarily depending on a few factors), the Henessey 750 package should have put down around 714/715 to the wheel. Or they could bill it as the Henessey 682 package lol, 682 being the crank hp using the 5% powertrain loss their stock camaro showed. By the 750s drivetrain loss percentage the stock one would have only made 393rwhp, which is actually pretty close to what some of the autos put down.
Maybe they should just stop manipulating so many numbers and just advertise what the car made at the wheel before and after parts install + tune.
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2000 Miata - aventi storm wheels, roll bar.
2019 Mustang GT pp1 - svt pp2 wheels, mbrp cat back, sync 3 upgrade, p1x procharger + stg2 intercooler.
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2017 Corvette Grandsport (sold) - untouched.
2006 GTO (sold) - iat relocation, air box mod, monero side marker lights.
