Author Topic: Double Clutching in Modern Vehicle  (Read 2591 times)

Glenstache

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Double Clutching in Modern Vehicle
« on: March 29, 2017, 12:52:37 PM »
Question for the mechanical wonks out there: Is double clutching on a downshift in a modern manual transmission worth it? Does it reduce wear on drive components?

I understand that synchros in a modern transmission remove the *need* to double clutch.

MightyAl

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Re: Double Clutching in Modern Vehicle
« Reply #1 on: March 29, 2017, 01:27:43 PM »
Double clutch or rev matching is used on vehicles with no synchros.  This is mostly used in racing to increase the strength of the gears in different manual transmissions for racing.  When you remove the synchros you then have room to increase the width of the gears.  Without synchros you need to match the speed of the engine to the speed of the gears in the trans in order to get smooth engagement otherwise you grind. 

Some people believe they get less wear and tear on their synchros from double clutching or rev matching but really the wear on conventional synchros is minimal at best.

I guess this is all a little clunky in my explanation but you can rev match without double clutching you just need to hit the gas while shifting.  I used to do it all the time just to see how good I could get at it.

HipGnosis

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Re: Double Clutching in Modern Vehicle
« Reply #2 on: March 29, 2017, 08:49:59 PM »
Synchros in a manual transmission remove the need to rev match.

MightyAl covered the rest.

JAYSLOL

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Re: Double Clutching in Modern Vehicle
« Reply #3 on: March 30, 2017, 01:48:30 AM »
No need to double clutch in modern cars.  I got 330k out of the clutch in my old Toyota compact, never double clutched, and drove it hard and towed a boat with it.  4spd manual is still tight as new.

Eucalyptus

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Re: Double Clutching in Modern Vehicle
« Reply #4 on: March 30, 2017, 03:20:59 AM »
I suspect that if there is a benefit, it will be pretty minimal. There are potential costs to double clutching. Eg:
- you could spend more time out of gear.
- increased engine revolutions
- more focus on double clutching, means that you as the driver can't focus on other things, which may have more effect on your hypermiling.

Its probably all a wash. Until you are already an expert hypermiling driver, I doubt a slight reduction in wear and tear on your gearbox will make up for what benefits you could get from hypermiling well. I would spend the effort there

BlueMR2

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Re: Double Clutching in Modern Vehicle
« Reply #5 on: March 31, 2017, 05:19:35 PM »
After your synchros are shot you can extend/avoid the need for cracking open the gearbox by double clutching...  When I bought my car the synchros were on their last legs in 2nd and 3rd already.  A couple years later they were toast and I was looking at a gearbox rebuild.  I learned to double clutch instead.  Now, many years later the gearbox is still unopened.  :-)