Relsek

I've been reading around the forum on the subject of horsepower loss differences between the auto and the 6 speed. I don't know what to believe, I keep reading different opinions.

Here are a few quotes from various threads.



Not to mention, I think the guy that ran my car on his dyno told be it loses something like 30%.

I'm not trying to start a fight, just wondering if anybody really knows.

Kevin

Z06seal

Nobody really knows. I keep at 15% for the M6, 20% for auto. that's how I've done it on my auto trans am, and thats how I do it on my Z06

Ultimate_Respect

Most of these people really do not know what the true loss is with the A4 vs. M6 really is. Most people who drag race have auto's for a reason it is something to think about...

C5XTASY

I believe that may be for repeatability.
Ed

oh1vette

So many variables.
I can tell you my 01 M6 coupe dyno'd at 291, so 16.8% loss....

wcsinx

Yes, it's called ease and consistency.

robert miller

Auto here and love it.

madmatt9471

General rule of thumb is:

15% drive train loss for manual 6 speed tranny's

20% drive train loss for auto's

There is this formula as well: remember you have to have your RWHP from the dyno in order to estimate your Crank HP

Auto/A4 is:
RWHP divided by .82 for Estimated Crank HP

Manual is:
RWHP dvivded by .86 to get the estimated CRANK HP

Thanks,Matt

rebelheart

It is also far easier the get a good consistant launch with an A4 and it shifts quicker than an M6.

skyavonee

You contradict yourself. Dividing by .82 assumes a 18% loss (1.00 - .82 = .18) and dividing by .86 assumes a 14% loss by the same math.

Z06's seem to consistently exhibit losses of ~13% +/- 1%. I'm not sure if non-Z06's with a manual trans would be any different.

madmatt9471

Can't shift fast the an AUTO!

That's why I got an A4 and I have always raced with an Auto

And let me tell you! what RPM Transmissions can do to a 4L60E A4 is amazing=Bullet proof

Thanks,Matt

DevilDog II

You'll never miss a shift with an A4. Most of the guys I know who drag race on a regular basis with an A4 are running faster than the M6's.

madmatt9471

That's why I said GENERAL rule of thumbs is 15% for Manual and 20% for an Auto! It's a GENERAL rule!

So I posted a more ACCURATE formula by a shop that build transmissions and other drivetrain parts - sorry that it left a 1% difference for you or others -

I suggest to look away from my post or your eyes will fall out and you guts will rot out - it is destructive

Sorry could not resist It's just a formula and it works for guestimations

REMEMBER: Every DYNO reads different too, they Dyno you used could very well read lower than the one I use use or flip that statement around. So it is all relevent!

Thanks,Matt

madmatt9471

I forgot to mention that:

YES! the C5 Z06's transmissions "ARE" different they are a MN12 and they have different gearing than the standard MN6's,

In addition to that, the rearend in the C5 Z06's are different as well, they are built with harder parts for racing purposes!

The C5 Z06 is also much lighter than the standar C5's plus a few other differences, well obvious differences

I hope this helps some

Thanks,Matt

skyavonee

You seem to be taking my correction personally and I'm not sure why. The point I was trying to make is simple - why post two different formulas when you know one of them to be less accurate than the other? It's counterproductive.

madmatt9471

No! No sweat! That is why I posted the funny part in the middle!

Well the reason I posted both is because both are being spoken about

Also because, when I am at a shop most people will remember the 15% or 20% estimation for their Vettes or vehicles, when they get their Dyno sheet, rather than the FORMULA! So they can quickly estimate their Crank HP

It's all good. Not to worry! Have a good day, and be safe in the rain!

Thanks,Matt

robert miller

Mike, Matt is one of the best guys on the forum to try and help any one at any time. I am sure he didnt mean nothing personally on you are to your statement....

brendan.9

only one way to tell do an engine only dyno than put it in the car and see the loses you never know what the actual engine makes you hope its 350 but it could be more or less!

Dominic Toretto

There is no "across the board" definite answer. Two people can have the same car same weight, same drivetrain and have different dyno numbers. Some variables include:

Elevation
How tired the car is
Heatsoak
Plugs and wires
The dyno it is on

To name a few. So the best answer is to actually just worry about YOUR dyno and go from there.

-Alex

Vega$Vette

And you have to realize the power loss is not a linear equation.

A 400 flywheel HP may loose 15% of the 400 hp (60 hp required for drive train friction etc). But a 600 flywheel hp may only loose 10% if it take 60 hp for the drive train. However when the power goes up the friction goes up so it will take a little more then the 60 in this example.

Now think about an extreme. A 1000 hp. does not take 15% or 150 hp for drive train.

Bottom line is all that really matters anyway is RWHP