RWH vs BHP

[mynewviper]

Thanks again VCA for your help as you've really been a lot of help. Have a friend who had a car with 650 Hp on the Dyno and had wondered what his Engine HP would be. He also asked if the HP would be different in a 4 speed vs an automatic. I told him there must be some type formula but that if anyone knew then it would be someone in VCA. Once again thanks for your help.

 

[Viper X]

Drivetrain loss in a Viper is generally accepted to be between 12% and 15%.

A car with an automatic trans normally looses much more in the "drivetrain" than a manual trans. It will depend upon the car and the trans, but 20% would be a likely number, perhaps more.

Dan

 

[Canyon707]

I was told by DC performance that a stock 04 viper will put down about 425 to the rear wheels so thats about 85 hp less that at the flywheel so thats about 17% if I did the math correctly.

 

[Matrix]

no, because no stock viper have 505 flywheel hp! Something like 480hp on flywheel is stock.

 

[dave6666]

The formula is this:

If your bank statement summary is printed in black ink, your car is to slow and you must immediately buy parts to make it faster.

If your bank statement summary is printed in red ink, your car is to slow and you must immediately buy parts to make it faster.

 

[Flyntgr]

What Dave said is 100% true.....

 

[grcforce327]

Filing bankrupcy on the home and business, your car is screaming fast!!!

 

[HI-NOS-Viper]

no, because no stock viper have 505 flywheel hp! Something like 480hp on flywheel is stock.

You have proof to back this up? You really think Dodge would put the numbers of 505HP if that wasnt the case.
I am also not saying the numbers are exact either, but I dont think that you would get a 480hp crank srt viper. Some have shown to be higher in the 510-515 range stock. I dydnoed completely stock at 435rwhp so that would put it about 510hp with 15% drivetrain loss.

 

[Art 138]

MYNEWVIPER: Last Saturday at the VCA Dyno day I pulled 650RWHP; I was advised to multiple that number by 1.12 which gives 728HP at the flywheel........

 

[fqberful]

The generally accepted values are 17% with a stick and about 22% with a slush box. These can vary a couple percent. My dyno experience over a number of years pretty much supports these values.

Next time you're on the chassis dyno have them do a "negative pull" if that particular dyno is capable of it. That will yield drive-line loss as a percentage and give you an idea what your losses really are.

And for those that believe MOPAR hp ratings, over the years they have been a tad bit liberal with those. A test mule engine that's machined perfect and really tweaked with headers or open / cat-less exhaust probably makes the mark. Production tolerances and other environmental variances generally have a loss effect. I suspect this is true of all manufactures. Unfortunately it's not like the good old days back in the 60's and early 70's where they intentionally rated them low at 4500 rpm and tricks like that to help with insurance and company racing policies.

 

[grcforce327]

You race the car at the wheels,not the flywheel.It must give some people a big boner to say the higher( motor) #,then they get smoked and go ! If the flywheel # is that important to you,pull the motor and run it on an engine dyno and put an end to all the guessing!