OK now I am almost positive the vette has less drivetrain loss than the FBody. Can someone chime in here...

I think FBodys are around 15-17 depending on tranny, etc

Arent vettes around 10-12??

 

Yes, have the doubters pick up the Dec issue of Motor trend. There is an article about this in the vette vs viper vs ford gt.
Robert

 

the thing is there is no SET value for any car. Even two identical cars will likely have a different percentage loss. This is for many reasons.

Also the percentage loss isn't fixed, as not all parts of the drive train are friction bearing. Think about it, the main propshaft require x amount of power to rotate it. By adding more HP the propshft does not become bigger or heavier so it will not require more HP to rotate it. However the couplings on either end are firction bearing, and as more force is applied to them more power will be lost.

So it really should be a diminish percentage loss. However there is no way of knowing what the deminishing rate should be.

The best general estimate I've come across for manual cars is 12% + 10bhp. This means it loads lower BHP cars to a greater extent.

If you want to know what your car looses then here is one possibility of taking an educated guess.

Assuming the GM figure of 345bhp SAE Net is accurate. You need to dyno your car on a dyno that will produce compariable numbers. A Mustang dyno should be a better bet over that of a dynojet.

You need to ensure that the numbers are fully corrected to SAE standards.

You can then work out how much loss there was, e.g.

300rwbhp means a loss of 45bhp. Or a loss of 13%

If you modify you car and it then dyno's 350rwbhp. You know the minimal it is making at the engine will be 350 + 45 = 395bhp. You can also factor in a 13% loss as well. 350 / 0.87 = 402bhp. Then just make a mean average of the two numbers.

Remember this is still a guess, but it will at least be educated. Just remember if you are using manufacture claimed figures, they will in the US be quoted as BHP SAE Net. Different rolling roads derive bhp differently because the measure torque in a different mannor. And correction factors for temp/humididty/altitude should all be included.

A dynojet can easily give a rwbhp number of 20+ higher than a Mustang dyno. However the car will not actually be any more powerful.

So 10-12% loss I would say is a bit of a stretch for a rwd car.

 

Agreed. Additionaly, our local Dyno jet has recently added new software. Seems Federal regulations have changed and there is a new standard for measuring HP. They went on to say that my current Dyno pull will be down approx 10hp from old method. This is the way the new cars are being measured. In conclusion, I think the Dyno Jet is closer to real numbers now, if in fact not right on.
Robert

 

I was always under the impression that f-bodies had LESS drivetrain loss due to the solid rear vs the transaxle and IRS of the vette......

 

Yea, I was almost convinced of that also, but Motor Trend says the vette is 12/13%, so...
Robert

 

Thats the same thing I thought.........

 

the vette loses more power thanks to IRS. the average t-56 power loss is said to be around 12% which would explain why manuals dyno so much bettter then the autos.

that being said, u CANT measure drivetrain loss by taking manufactures hp specs and then running it on the dyno... (everyone should know by know rated and actual hp are very different things)

 

Yea, rated BHP is the engine on a dyno before going in the car. so, it does actually work pretty good. get the new Motor Trend for insight.
Robert

 

Ive just always went by this method....

RWD MN6's loose 15%

RWD a4's loose 18 %

As far as the Fbodys really dynoing higher than the C5 I cant really say....

I asked my local tuner this question...They specialize in F bodys and mustangs and the ocassional vette..

They told me that honestly with the LS1 from the HUNDREDS of cars that they had dynoed that were camaros...Firebirds and C5's....

It really didnt matter if the car was an mn6 or a4 or if it was a C5..camaro or bird...

They said some cars just got stronger engines than others...

They said the lowest they normally saw was 280 rwhp on there dyno jet from stock LS1's....And it would be mn6's as well as manuals...F bodys and Vettes...

They said the highest they ever saw was 305 rwhp....Once again sometimes a4's and some times mn6's...

My 2004 a4 got 299 rwhp...

They said I should be very happy with those numbers.

They also told me that all the stories of F bodys and C5's having 310-315 rwhp bone stock was 99% bull crap and most of the numbers were not SAE corrected or not smoothed down to 0 percent....

They showed me how with my lines not totaly smoothed how easy it would be to tell people that I dynoed 310 rwhp and no one would hardly be able to look at the dyno and tell the differance...

They also showed me how easy it was to get that same 310 rwhp dyno to say 320 rwhp if it wasnt SAE corrected.,

They told me that all the C5's that they had ever dynoed put down EXACTLY the same averages as the F bodys...

The only differance was that they dynoed 10 times more F bodys than C5's.


When you go to Chevy loyalist sites like this one.....They'll have you beleave that ALL LS1's dyno 300-315 rwhp..And can run 12's stock.

And that all 2002 C5 Z06's dyno 355-365 rwhp and run 11's stock.

Unfortunetly the rwhp numbers are 10 to high and the track times are a good 3 tenths to low NORMALY.

 

I agree with some of your post. I know the owner of the dyno I take my car to, no dyno tricks were done WHATSOEVER, and it dynoed 321 331 with just a lid....About the running 12's, I ran high 12's with only a lid. I still find it humerous when some people question these cars abilities just because "theirs" couldn't do it.

 

Im not questioning you....Theres plenty of C5's that run 12's bone stock..Also plenty of Camaros.

All Im saying is that it IS IN NO WAY THE NORM..

1 OUT OF EVERY 500 f BODYS WILL ACTUALLY BE ABLE TO RUN 12.9 SHOW ROOM STOCK.

Your car would have been around 13.1 bone stock....That is the high side of Birds...But can be done by GREAT drivers on GREAT tracks...

Your Lid was good for 1-2 tenths....

I dont doubt your numbers at all and personaly beleave that the bird is a LIL quicker than the camaro anyway.

Your lid may have been worth 5 rwhp...Or it may have been worth 15 rwhp..No way to really know.

ALL IM SAYING IS THAT THERE IS A DIFFERANCE BETWEEN CARS LIKE YOURS....AND MAYBE YOUR TRACK OR DRIVING SKILLS..

THAN THE AVERAGE FBODY AT THE AVERAGE TRACK WITH A DECENT DRIVER..

I can go to different sections on this site right now and post NUMEROUS people who never broke 13.6 stock...

There quite a few F body guys still in the 14's.....Maybe they just cant drive...Maybe there cars messed up...Maybe there tracks at a high DA...

The point is that for every person like you that ran a 13.0-13.2 bone stock...Theres another person ON THIS SAME FORUM that post a best of 13.9-14.1 bone stock...

Then the other 90 % of people who are at normal tracks with normal driving skills and normal bone stock power ranges of 280 rwhp-305 rwhp...

will run 13.4-13.7....

I had a supercharged 1998 camaro before I ever got my Vette and am fully aware of what F bodys are capable of....

BUT IM NOT ONE TO CARE ABOUT THE BEST TIMES PEOPLE GET FROM CARS...I CARE MORE ABOUT THE AVERAGE.

Is it possible that you got a factory freak with 315 rwhp bone stock? HECK YEA IT IS.....

There was aguy on here a few weeks ago that got a 12.5 out of a bone stock C5......Thinks he might be the world record holder....

point is....yea thats kool. he got a factory freak. But in no way dose that represent what all C5's are capable of.

 

Sure there is, use same dyno, dont change your tuning, and do a before and after pull with the lid, it is easy to swap stock vs ported lid.