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Most accurate estimate of AT drivetrain loss??

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Old 06-15-2010 | 08:02 AM
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Default Most accurate estimate of AT drivetrain loss??

I need to know best estimate %, TIA
Old 06-15-2010 | 12:28 PM
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Anybody?
Old 06-15-2010 | 04:51 PM
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It would be a real project to get that info. You'd have to do a dyno run with the MT, swap the engine into a car with the AT, and do another dyno run. Very few serious tuners have the AT, so I'd put the chances of someone having done that are about zero.

The torque converter locks up at some point in the acceleration, so the difference would be zero after that point. IIRC, the torque converter only locks up in the top three gears.

I thought it might be helpful to look at the fuel mileage for city driving for the AT vs the MT, but that's complicated by the different axle ratio used.

In short, I doubt anyone's got anything better than a guesstimate. It's going to vary quite a bit depending on how you drive the car. For me, the difference is probably negligible. For someone with a heavy foot, I'd say around 15%.

Last edited by winchman; 06-15-2010 at 04:57 PM.
Old 06-15-2010 | 05:26 PM
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I personally have a 5at. On a stock block when I first boosted made around the same power at the same boost as a 6mt. Granted I'm running twin gt30's and a higher stall torque converter. So all results will very with application like mentioned before.

Every shop likes say drive train loss of 15% or around that.


You probably will not get a straight answer on this forum. Most will just make fun for driving a auto***g ot.... sports car ...lalalalala......
Old 06-15-2010 | 07:10 PM
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That's easy. Just find a stock dyno chart and divide.
Old 06-15-2010 | 07:23 PM
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Originally Posted by winchman
It would be a real project to get that info. You'd have to do a dyno run with the MT, swap the engine into a car with the AT, and do another dyno run. Very few serious tuners have the AT, so I'd put the chances of someone having done that are about zero.

The torque converter locks up at some point in the acceleration, so the difference would be zero after that point. IIRC, the torque converter only locks up in the top three gears.

I thought it might be helpful to look at the fuel mileage for city driving for the AT vs the MT, but that's complicated by the different axle ratio used.

In short, I doubt anyone's got anything better than a guesstimate. It's going to vary quite a bit depending on how you drive the car. For me, the difference is probably negligible. For someone with a heavy foot, I'd say around 15%.
Originally Posted by k6750gsxr
I personally have a 5at. On a stock block when I first boosted made around the same power at the same boost as a 6mt. Granted I'm running twin gt30's and a higher stall torque converter. So all results will very with application like mentioned before.

Every shop likes say drive train loss of 15% or around that.


You probably will not get a straight answer on this forum. Most will just make fun for driving a auto***g ot.... sports car ...lalalalala......

I really appreciate it fellas. A best guess is all that i require as i know any exact figure would be next to impossible to obtain.

You guys are pretty much aiming for the same part of the target as myself, as i figured 15-18% would be the best guess. I just thought i would put it out there to see if maybe someone would have nailed it down to a more accurate and proven percentage.

As for the AT haters, ill gladly argue with anyone on here who thinks an AT is worthless in comparison with the MT. All disadvantages of the AT can be compensated for with upgrades, however the MT/driver can never obtain the perfection in flawless shifting supplied by the AT, which is why we are seeing more and more supercars with clutchless trannys.

But this argument has been had time and time again. Point is, you'll find that most who hate on autos as far as performance aspects go have no idea what they're talking about.

Thanks again fellas.
Old 06-15-2010 | 07:28 PM
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Originally Posted by davidv
That's easy. Just find a stock dyno chart and divide.
Been done. Yielded results that fall into above mentioned %'s, just wanted to see if somehow, someway, someone had done some kind of solid testing.
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