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Old 11-20-2007, 09:50 AM   #1
XFi
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Replace Torque Converter with a Clutch?

(oops, torque convertEr?)
Hey,

I've been throwing some ideas around for my spring project (97 Escort Wagon) and I have been considering both a 5spd Transaxle or an Automatic. I known that the 5spd will be victorious in a strict MPG match against the Auto, but I was thinking about how an automatic trans could be modified to be more efficient.

I remember reading a magazine article, probably a CarCraft or HotRod Mag back in the late 80's, about someone modifying thier trans and replacing the torque convertor with a clutch. I know they did this for performace reason (infinate stall speed), but what kind of advatages would this have for MPG?

You would need to press in the clutch only when stopping and starting out. Seems to me...There would be direct 1:1 power with no slippage. Shifts would be quicker than manual and less power would be lost by falling RPMs. Wouldn't have to loose MPG by waiting for the torque convertor to 'lock up'.

Does anyone else remember anything about this or have any leads to article/info? What are your thoughts?
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Old 11-20-2007, 09:59 AM   #2
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Originally Posted by XFi View Post
(oops, torque convertEr?)
fixed

This would be very interesting - I've never thought of doing something like this.

An immediate downside I see is that it would probably be VERY jerky during shifts - if you can deal with this (and I could), nothing else jumps out at me right away...
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Old 11-20-2007, 10:08 AM   #3
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Thanks for fix'n the spelling

Oh, also another benefit would be no load on the engine when at idle (it would be disconnected from the trans completely).
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Old 11-20-2007, 10:09 AM   #4
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Here is some info: http://www.autozine.org/technical_sc...l.htm#Sensonic

They've been around for a while. The SMART car uses a automatic clutch (no torque converter). However, with the newer technology of today and the ability of modern torque converters to lock up it has become less of an issue as far as mileage goes.

I don't think there are any universal kits or anything that you could fit to your car without major work.
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Old 11-20-2007, 10:17 AM   #5
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Well there would be no flywheel for the clutch to "hook-up" with and where or what would you do with all the AT fluids? There are some pretty complicated automatic "clutch" set ups including 3 and 5 plate style. I guess you are also talking about some kind of "clutch pedal" assembly also? I don't really see any advantage or real world workable solution with this option.

Since you are modding such a "lite/light car"...maybe a motorcylce transmission would work! You can shift most of those with out using the clutch on the upshift...and you would save some serious weight. It would also have the mechanism to disengage the cluth at a stop. Otherwise a very expensive sequential shifting tranny could be mated to your engine of choice.
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Old 11-20-2007, 10:20 AM   #6
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Quote:
Originally Posted by Daox View Post
Here is some info: http://www.autozine.org/technical_sc...l.htm#Sensonic

They've been around for a while. The SMART car uses a automatic clutch (no torque converter). However, with the newer technology of today and the ability of modern torque converters to lock up it has become less of an issue as far as mileage goes.

I don't think there are any universal kits or anything that you could fit to your car without major work.
Thanks for the link, but the transmissions specified on that page seem to be manual with an automatic clutch fitted into them. I am talking about the opposite of that...an automatic trans with a manual clutch to replace the torque convertor.
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Old 11-20-2007, 10:30 AM   #7
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Originally Posted by DarbyWalters View Post
Well there would be no flywheel for the clutch to "hook-up" with and where or what would you do with all the AT fluids? There are some pretty complicated automatic "clutch" set ups including 3 and 5 plate style. I guess you are also talking about some kind of "clutch pedal" assembly also? I don't really see any advantage or real world workable solution with this option.

Since you are modding such a "lite/light car"...maybe a motorcylce transmission would work! You can shift most of those with out using the clutch on the upshift...and you would save some serious weight. It would also have the mechanism to disengage the cluth at a stop. Otherwise a very expensive sequential shifting tranny could be mated to your engine of choice.
The flywheel would be as simple as replacing the flexplate, but yes...there are numerous complications that would arise with doing this. Modification of the 'bellhousing' and input shaft? Just a thought that hasn't been thought out all the way But still if it could be done, would it be worth doing? Would the automatic transaxle be as good as the manual at this point in reference to MPG? Or would there still be too much power lost in the fluid transfer of the Automatic. Just thinking out loud again...
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Old 11-20-2007, 10:37 AM   #8
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Well even tho engagement would be "clutch controlled"...gearing would still be planetary and be controlled by servos/fluids/ect. I don't think it would be as efficient or light for that matter.

The Motorcyle tranny would be novel tho.
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Old 11-20-2007, 11:41 AM   #9
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Originally Posted by theclencher View Post
yood lose some rashios and itd be lotsa work

i'd go 5 speed, you can get the ratio you need with it

also it's probably quite a bit lighter
Yeah, Yeah...I know.

(thanks for not telling me to 'stop re-inventing the wheel')
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Old 11-21-2007, 01:25 PM   #10
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The only auto gearbox swap that might make sense to me is the VW DSG box... (although it fitting the Escort and being priced reasonable are pie in the sky) -- still an excellent design that pretty well eliminates all downsides to slushboxes except no EOC.
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