06windveilgt

So after a while of being on this forum i have come to a conclusion that if you have an automatic transmission you lose power. If I'm correct how much horsepower and torque am I losing and has anyone done a dyno on a stock 05-07 Automatic GT? If so, what were your numbers if you don't mind me asking.

06windveilgt

anyone?

6xStang

Automatic trannies can result in some lower performance times, but not because you lose "power" as much as you lose efficiency. There is some slip off the line, and some slip between shifts, which hurts measured acceleration times....but once "locked up" they are delivering all the "power" that you would get with a manual. I think the dyno numbers should be comparable, but a side-by-side comparison might be interesting.

Newer, high performance autos (sadly none sold by GM or Ford, I think) can be just as fast or faster than manuals. Porsche, BMW, and DC come to mind as offering some pretty fast automatics.

06windveilgt

Thanks 6xstang. I know what you are talking about when you say some foreign cars are faster auto then manual. I read in a magazine and believe it was the Porsche 911 Turbo auto which was faster than the manual.

07AlloyGT

don't quote me on this but i've seen this somewhere on these forums:

manual - 275-280rwhp

auto - 265-270rwhp

don't really know how true that is but take it for what it's worth.

xbone

From what ive read the auto trans can shift faster than a human with a 5 speed. Its computer controlled after all, and no fear of missing a shift. I talked to a Ford tech about these new trans and his opinion was the older 4R70 was a stronger trans for racing than the new 5r55s, but the new auto is better than the new 5 speed because of quality problems. I think the 5r55s is not going to be a 100k trans because its sealed and more difficult to service, but only time will tell. Just my .02.

2k05gt

Those HP Numbers areabout right, I have a friend that has an 05 Manual and Mine is an Auto and we have all the same Mods.JLT II SCT Tune, UDP, 4.10 Gears and we both have around 30K miles andhere were our times at the track

Maurice and I ran 3 times
Run one -2K05GT 13.51 @ 101.90 Maurice 13.69 @ 103.00
Run two - 2K05GT 13.55 @ 101.44 Maurice 13.56 @ 103.71
Run three - 2K05GT 13.55 @ 101.83 Maurice 13.63 @ 103.42

awakeinAZ

I agree that the torque converter looses some hp but, 2k05GT it says in your sig you ran 13.363 @ 103.39. Isn't that right on the money to the Maurice numbers? Avg of your 3 versus his 3 are 1.65 MPH. Not a big difference!

Sleeper05

Automatic transmissions are heavier, and have more parasitic loss than standard transmissions. This results in a loss of rwhp (though the engine hp is the same) from having to turn more mass, as well as a minute negative effect from having more dead weight to move under acceleration.

The efficiency argument is false, as automatic transmissions are actually *faster* at shifting than even the most proficient driver with the shortest throw shifter, doing so in around .15seconds, where a manual will take at least a quarter second to shift. Newer tiptronic style transmissions can shift in under one tenth of one second at the press of a button.

06windveilgt

thanks for the feedback guys and 2k05gt those are some impressice 1/4 mile times.