[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.

[RobbyBeefcake87]

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.

[Flexhorn]

I just had a stage 2 cam put in and it added 58RWHP

[oldman]

Originally Posted by RobbyBeefcake87

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.

Let me check and type at the same time (appreciate you checking my math).

751 - X =649
X=101 HP loss due to drivetrain. 101 HP = Y% of 751
Crank the number 13.5%

I did it from the two dyno numbers, so actually getting to believable. I personally believe the m6 is at 11 to 12% the auto is very gear dependent so say 14 to 16%.

Originally Posted by RobbyBeefcake87

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.

We both know that no stock LT1 puts out 433 RWPH. They are using Unicorn HP (STD) and even then 416 SAE is still on the very high side. What really messes them up is putting a FI engine on the same graph and correcting it to STD. Then the math blows up as you have noted and they have the same car with 5% drivetrain loss and 13.5%. LOL

Originally Posted by RobbyBeefcake87

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.

You get the prize

By eyeball the STD applied to this dyno run is 5.6%, assuming a super running LT1 m6 bone stock at 410 to the wheels uncorrected.

that would mean the 750 package is putting out an actual 641 RWP toss in the more realistic drivetrain loss of 11% we get 641 / .89 = 720 engine HP. So actually Hennessy should have just said 641 RWP and there is a 15% drivetrain loss (general rule of thumb, even though it is wrong) and 754 engine HP and NOBODY would question that math. But what a wicked wed we weave when one tosses a FI car, puts the read out in STD and tries to figure the relationship to the SAE rating the OEM has.

One final way to look at the numbers is the delta is 216 RWHP STD. I've already pointed out the CF is probably 5% so actual as measure RWHP delta is 205. Lets us the more useful 11% drivetrain loss crank the numbers and we get 230 engine. The car started with 455 HP and 230 engine is 685 HP.

Can't advertise that right?