Bearcat Steve

I've heard it said that GM's official numbers for driveline loss are 12% for the M6 and 15% for the A4.

detltu

Im glad someone realizes that driveline losses vary between cars. I get kind of tired of every magazine that tests rwhp saying this car is really making 500hp+ when in reality it probably just has a more efficient drivetrain. Any ways thanks for those numbers I have never heard the specifics for the F-Body transmissions. Seems like a more valid estimate than the usual 18-20%

Fbodfather

actually, according to John Heinricy (chief engineer) it was 18% on both 6-speed and auto..........

demonspeed

Then why would an identical optioned car that is a 6 speed trap higher than an auto? Sure, they might e/t practically the same, but time and time again, 6 speeds trap higher - because they are getting more power to the ground, no?

JasonD

I want to say that if a decent aftermarket converter was used, that auto car would smoke the 6-speed in most cases. Someone chime in.

demonspeed

I'm talking stock for stock though. I'll just use some modded cars for example...

My 2000 SS only had a catback and lid (before the 4.10's). At the time, it had only gone a best of 13.2 @ 108. I raced my buddies 2000 WS6 A4 who had a small cam, long tubes, catback, and 'verter - and went low 12's @ around 110. We were dead even on the highway. Sure, it was quicker, but the trap proved that it simply wasn't putting power to the ground, IMO anyway.

Please correct me if I'm wrong, but if the M6 and A4 were both losing the same % through the driveline, then they should e/t and trap appx the same stock for stock and car for car.

danno02SS

Both 6M and A4 cars may ET the same but trap differently because of gearing.

A4's are easier to get out of the hole and have tall 1st and 2nd gears. They will usually do better than an M6 in the 1/8. Down the 2nd 1/8, however, the 4L60E shifts into 3rd and falls bellow its powerband. The M6s has a taller 3rd gear that keeps the engine in the higher RPMs and 4th is hit before the end of the 1/4.

The additional gear is why the M6 traps higher. That and it puts down roughly 10rwhp more to the ground.

number77

Scott, those are some cool details! Now I want a 99 Camaro with the 1LE package. I also didn't know about the block color. So they technically weren't "ls6" blocks?

Bob Cosby

They might have used 18% for each, but that is almost certainly just a fudge factor, as the A4 will have more parasitic loss than an M6. That is the main reason you see lower traps with the A4. However, a good auto can and often does produce better ETs. One reason is due to the ability of a correctly-matched converter to keep the engine much closer to its powerband. Also, the average A4 can easily out-shift the average M6 driver....and a properly modified A4 will outshift even the best M6 driver.

demonspeed

This makes much more sense. I always figured the gearing in the tranny was pretty much similar between the two other than overdrive. I'll still take my 6 speed anyday though

That is, unless I was building a dedicated drag car.

And no matter what is said, there must simply be more parasitic loss with an auto than there is a manaul.

97z28/m6

not on a road course.

RussStang

Correct. There is no way I can see both drivetrains having the same driveline efficiency. I have never seen an A4 dyno as high as an M6.

I wonder just how well an automatic could be programmed nowadays for a road course if automatics were allowed in the rules? I would bet a road course programmed auto would have shift parameters that resembled nothing like a conventional automatic does.

Bob Cosby

LOL. Touche'. I should qualify my statement by stating that I am referring to acceleration.

RussStang

I have never seen an Fcar that wasn't broken making rear wheel figures that would better corroalte its 305 crank rating, regardless of trim. They all dyno high, and they all dyno around the same, regardless of trim. The reason some LS1 cars put down around 320 at the wheels is because the 01s and 02s had the LS6 intake manifold from the factory, and with an M6 some of them are known to touch this high of a number straight out of the showroom.
Some of the fastest recorded stock F-Body times have been down with factory stripper z28 cars.

Red, I have never actually seen a supposedly F-Body LS6 block apart, but I have read from several reputable machinists that the blocks are indeed LS6 blocks, as they have the better breathing areas around the cylinders. Something like 10% of 01s and 25% of 02s got the LS6 block if I recall correctly. There has been alot of debate over whether the LS6 block itself actually increase engine horsepower, but the consensus seems to be that if it does, it is very, very minimal.

Fbodfather

not on the 99s........2001 and 2002