double clutching
Originally Posted by ez
It has nothing to do with the fluid or pumping. The reason is in point 1 from my post above. To state it another way:
When downshifting, the input shaft speed needs to match the output shaft speed (connected to the wheels). With the clutch disengaged, the clutch plate/input shaft assembly spins free. The only way to speed it up to match the output is to engage the clutch and blip the throttle.
Absolutely required in some gearboxes, the best way to do it in most gearboxes.
When downshifting, the input shaft speed needs to match the output shaft speed (connected to the wheels). With the clutch disengaged, the clutch plate/input shaft assembly spins free. The only way to speed it up to match the output is to engage the clutch and blip the throttle.
Absolutely required in some gearboxes, the best way to do it in most gearboxes.
Are we talking about rev matching or double clutching? I understand the concepts and benefits of rev matching, but my question is.. why do we need to double clutch if we have a fully functioning and properly adjusted clutch hydraulic system?
Originally Posted by marksae
Are we talking about rev matching or double clutching? I understand the concepts and benefits of rev matching, but my question is.. why do we need to double clutch if we have a fully functioning and properly adjusted clutch hydraulic system?
Rev matching is part of double clutching. A perfect rev match downshift can be done without the double clutch part, but if so, you are still putting unnecessary wear on the synchros. The double clutch downshift technique prevents wear on the synchros during a rev matched downshift..
if you don't understand what we're talking about, then you really don't understand exactly how a manual transmission works.
read this:
How Stuff Works: Manual Transmission
Last edited by Wheelhaus; May 11, 2006 at 08:02 AM.
What we are saying is that double clutching is the proper (sometimes required) way to rev match. And thanks to Haus for the thorough explanation 
Originally Posted by marksae
Are we talking about rev matching or double clutching? I understand the concepts and benefits of rev matching, but my question is.. why do we need to double clutch if we have a fully functioning and properly adjusted clutch hydraulic system?
Evolving Member
Joined: Jan 2006
Posts: 166
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From: California
A lot has been mentioned on why and how but I think it bears repeating that as far as our evos go, there is no need to do this in our cars. Folks have mentioned that double clutching will save you wear on your clutch, but it actually will increase wear. Assuming two perfectly rev matched downshift on a syncrho'd car (e.g. evo) both with and without double clutching, there is no additional stress on any part, except with a double clutch you engaging disengaging the clutch twice, hence additional wear.
That does not mean its a useless skill, just not something you will need to learn for any modern street car (including that 240sx from the origional poster). Remember also that heel toeing should be your first priority (since it applies to every car with a manual), double clutching can always be added on after you have mastered that. This is how i learned.
On the other hand if you race or want to drive formula cars or a full out race car like some speed WC or grandam cars then practice up now. It will make life a lot easier ahead, just figure in additional wear on the clutch for your evo A full race transmission is a very big investment so there aren't many amatuer level cars/teams that will touch a dog gear transmission.
That does not mean its a useless skill, just not something you will need to learn for any modern street car (including that 240sx from the origional poster). Remember also that heel toeing should be your first priority (since it applies to every car with a manual), double clutching can always be added on after you have mastered that. This is how i learned.
On the other hand if you race or want to drive formula cars or a full out race car like some speed WC or grandam cars then practice up now. It will make life a lot easier ahead, just figure in additional wear on the clutch for your evo
A full race transmission is a very big investment so there aren't many amatuer level cars/teams that will touch a dog gear transmission.
Sorry for all the confusion guys. I went back and read most of the thread in detail. I didn't know engaging the clutch in neutral helps "sync" the engine speed w/ the tranny input speed perfectly before the downshift. I always thought a perfect single clutch heel/toe downshift does the same thing. Now I got something new to practice.
Who said that double clutching will save wear on the clutch?? I must have missed that part.
As for clutch wear, the extra plate wear would be negligible since it is not slipping under load. There will be extra wear on parts that actually control clutch engagement...mainly the release bearing. But not near the wear as if someone held the clutch pedal at every stoplight...which is a common bad practice.
To say that synchro wear is not an issue is flat out technically wrong. A synchro cone is a clutch, so that fact that you cited clutch wear even supports the fact that working a synchro wears it out. Synchro rings are also softer than gears (like some brass in the Evo
), so they take the abuse as well on every non-matched gear selection.
Even if I were to concede that the added clutch wear is significant, I would then have to ask which you would rather replace: clutch parts, or internal gearbox parts. Having done many of both, I would say clutch.
This thread is so old...and the proper case for double clutching has been made so many times. I'm done...
As for clutch wear, the extra plate wear would be negligible since it is not slipping under load. There will be extra wear on parts that actually control clutch engagement...mainly the release bearing. But not near the wear as if someone held the clutch pedal at every stoplight...which is a common bad practice.
To say that synchro wear is not an issue is flat out technically wrong. A synchro cone is a clutch, so that fact that you cited clutch wear even supports the fact that working a synchro wears it out. Synchro rings are also softer than gears (like some brass in the Evo
), so they take the abuse as well on every non-matched gear selection.Even if I were to concede that the added clutch wear is significant, I would then have to ask which you would rather replace: clutch parts, or internal gearbox parts. Having done many of both, I would say clutch.
This thread is so old...and the proper case for double clutching has been made so many times. I'm done...
Originally Posted by heeltoer
A lot has been mentioned on why and how but I think it bears repeating that as far as our evos go, there is no need to do this in our cars. Folks have mentioned that double clutching will save you wear on your clutch, but it actually will increase wear. Assuming two perfectly rev matched downshift on a syncrho'd car (e.g. evo) both with and without double clutching, there is no additional stress on any part, except with a double clutch you engaging disengaging the clutch twice, hence additional wear.
That does not mean its a useless skill, just not something you will need to learn for any modern street car (including that 240sx from the origional poster). Remember also that heel toeing should be your first priority (since it applies to every car with a manual), double clutching can always be added on after you have mastered that. This is how i learned.
On the other hand if you race or want to drive formula cars or a full out race car like some speed WC or grandam cars then practice up now. It will make life a lot easier ahead, just figure in additional wear on the clutch for your evo A full race transmission is a very big investment so there aren't many amatuer level cars/teams that will touch a dog gear transmission.
That does not mean its a useless skill, just not something you will need to learn for any modern street car (including that 240sx from the origional poster). Remember also that heel toeing should be your first priority (since it applies to every car with a manual), double clutching can always be added on after you have mastered that. This is how i learned.
On the other hand if you race or want to drive formula cars or a full out race car like some speed WC or grandam cars then practice up now. It will make life a lot easier ahead, just figure in additional wear on the clutch for your evo
A full race transmission is a very big investment so there aren't many amatuer level cars/teams that will touch a dog gear transmission.
Originally Posted by r1elkins
just watch the fast and the furious...that will explain everything!
Originally Posted by CosmosMpower
Not needed, modern cars have synchros
Cosmos, you must not know how to read a thread. Give it a shot, you might learn something instead of making ignorant comments like that.
The topic of why double clutching (even WITH synchros-
) has been covered over and over. If you're going to post, especially in a good thread such as this, please at least contribute something useful.
FWIW, I just started practicing double clutching on the track this past weekend. I found it tough to do it naturally without having to think about it, since it's new, but I also still have trouble getting my big clodhopper feet to heel-toe, so I'm not good at either technique yet.
I tell ya what, there's nothing better than double-clutching the first 1-2 shift of the day when the tranny is cold. It slides in like warm butter every time...
I tell ya what, there's nothing better than double-clutching the first 1-2 shift of the day when the tranny is cold. It slides in like warm butter every time...
you're right... it's hard to get in the motions because it takes such a conscious effort... Are you using any specialized driving shoes or anything? They can greatly help your pedal feel and sensetivity. Puma makes some awesome driving shoes. Speed Cats, Future Cats, Grit Cats, etc.
I got some Pilot (or is it Piloti?) shoes that I use for racing, but when packing the car Saturday, I forgot to bring them, so I was wearing some running shoes that don't work as well. With my race shoes, I have much better pedal control, and there is no oversized sole sticking out and hitting the edge of the wrong pedal...
I bought some puma shoes and they sucked for doing heel/toe. My foot kept slipping off the brake pedal. I wonder if the sole needs to be "broken in" by scraping off the first layer.
Originally Posted by marksae
I bought some puma shoes and they sucked for doing heel/toe. My foot kept slipping off the brake pedal. I wonder if the sole needs to be "broken in" by scraping off the first layer.
I learned heel/toe using DC shoes with a nice big flat sole. It was much easier but it wasn't accurate enough. The Piloti shoes are awesome, my buddy Pat uses them. They have a much thicker sole than my Speedwells Boost_Lows or Grit Cats. Personally I like the thinner sole for more sensetivity.
Although I could do it with the stock pedals, I wanted them a bit closer so I made a curved aluminum plate that has an angled 1/2" flange so I can catch the edge of the pedal. I did the same thing on my STi and put strips of skateboard grip tape on it for traction. I'll take a pic and post it tonight.