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Driveline loss for an auto car vs. stick shift
Old 07-03-2014, 11:12 PM   #1
Fabman
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Default Driveline loss for an auto car vs. stick shift

I have always wondered what the driveline loss for an auto car is.
Over the years I have asked many people supposedly in the know and had many different answers ranging from 18% to 25%, but no generally accepted consensus.

Finally, I think I have an answer, thanks to some known quantities provided by our friends Dan Watts and AED.
I think we can agree that Dan's car makes good power and that AED is a reliable source for data.

Here is my logic;
Dan went from 744 rwhp to 689 rwhp going from a stick to an auto which is 55 hp drive line loss.

It is generally accepted that drive line loss for a stick shift car is 15% as evidenced in the following video.
https://www.facebook.com/photo.php?v=10204149056544591&set=vb.1171345951&ty pe=2&theater

In this case the Super snake loss is from 850 to 747 for a total of 103 hp or 15% loss w/stick.
So the widely accepted 15% loss claim hold true at least in this case.
Dan's car is making very close to the same numbers as this Supersnake so it makes a good comparison in my estimation.

Since 103+55=158 we can assume that is the total loss for an auto car making about 850 crank HP.
689 rwhp x 24% = 165.
689 rwhp + 165= 854 crank hp
Total loss for an auto in Dan's case is about 24% give ot take a few tenths.

Therefore I have drawn the conclusion that driveline
loss for an auto w/high stall converter is about 24% while 15% loss for a stick is validated by the above video.

If there is an error in my logic or math, one of you smart guys please help me out.....but I believe that what I have here is correct.

Maybe Shawn will chime in here and educate us.
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Old 07-03-2014, 11:26 PM   #2
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I think that what kind of auto plays a roll as well.. Glide, AOD, 4R70W etc etc..
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Old 07-03-2014, 11:33 PM   #3
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Quote:
Originally Posted by 98 Saleen Cobra View Post
I think that what kind of auto plays a roll as well.. Glide, AOD, 4R70W etc etc..
Thats probably true to some extent. I can only approximate using the data at hand.
I know a high stall also shows some additional loss, at least thats what I was told by a converter manufacturer.
I know that when I went from stock 5r55s and stock converter to a TCI Street fighter 5r55s and PI converter there was some additional loss,
though I don't have the data at hand to substantiate....
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Old 07-04-2014, 07:49 AM   #4
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I would imagine there is a substantial variance between different auto trannies. Even with the loss that happens from installing an auto, i'll take the benefits of the tranny such as better shifting and torque multiplication over the extra HP in a manual tranny.
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Old 07-04-2014, 02:29 PM   #5
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Quote:
Originally Posted by Simon View Post
I would imagine there is a substantial variance between different auto trannies. Even with the loss that happens from installing an auto, i'll take the benefits of the tranny such as better shifting and torque multiplication over the extra HP in a manual tranny.
I believe Dan has a 4R70W.
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Old 07-05-2014, 09:54 AM   #6
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Quote:
Originally Posted by Fabman View Post
I believe Dan has a 4R70W.
I have a 4R75W.
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