Rev Matching / Double Clutching
01-09-2011, 06:18 AM
#21
1st Gear Member
Join Date: Feb 2009
Location: MA
Posts: 116
You can double clutch if you want in order to sync the input shaft, but as many have said, it doesn't really buy you much for the effort.
Clutchless shifting is when you apply force on the syncro, it prevents you from going in gear until everything is in sync. Basically, you are on the throttle, just as you let off the throttle, the entire transmission has no tension for a moment. At this moment, you can pull it out of gear. If you try to pull it out of gear while the tranny has tension on it, you need the clutch. Once it is in neutral, rev match without the clutch. Once the RPM is where it should be for your speed and change in velocity, apply enough pressure against the gear that it will go in if you have synced it right. If your timing is right, it should not take much force, but if you are off, the syncro will try to lock you out. What you can do is rev slightly above the matched RPM, then apply a bit of force on the lever so that it will fall in just as the RPM hits the right spot. The problem with doing this is that it is very slow - like granny shifting. Secondly, it puts an unusual strain on your syncronizers and can definitely damage them. Back in high school I learned this from one of my friends. When I had a manual geo prism, I learned how to do this really well. It actually came in handy when delivering pizzas with a bad clutch that wasn't slipping at all but you had to pump it alot to engage it.
Clutchless shifting is when you apply force on the syncro, it prevents you from going in gear until everything is in sync. Basically, you are on the throttle, just as you let off the throttle, the entire transmission has no tension for a moment. At this moment, you can pull it out of gear. If you try to pull it out of gear while the tranny has tension on it, you need the clutch. Once it is in neutral, rev match without the clutch. Once the RPM is where it should be for your speed and change in velocity, apply enough pressure against the gear that it will go in if you have synced it right. If your timing is right, it should not take much force, but if you are off, the syncro will try to lock you out. What you can do is rev slightly above the matched RPM, then apply a bit of force on the lever so that it will fall in just as the RPM hits the right spot. The problem with doing this is that it is very slow - like granny shifting. Secondly, it puts an unusual strain on your syncronizers and can definitely damage them. Back in high school I learned this from one of my friends. When I had a manual geo prism, I learned how to do this really well. It actually came in handy when delivering pizzas with a bad clutch that wasn't slipping at all but you had to pump it alot to engage it.
Last edited by lundefinedl; 01-09-2011 at 06:22 AM.
01-10-2011, 01:18 PM
#23
2nd Gear Member
Join Date: Jun 2009
Location: Ohio
Posts: 300
My 2c worth is that double-clutch rev-matching on downshifts, while not necessary is an enjoyable lost art. Quite satisfying once mastered and it makes perfect sense to me to seamlessly match the revs and smoothly accomplish a downshift. I can go from 5th to 4th (or even 3rd) at 70mph with a double-clutch downshift and if I have the music up loud my passenger never even knows I did it unless they see my hand on the shifter.
01-10-2011, 06:42 PM
#24
3rd Gear Member
Join Date: May 2007
Location: Jacksonville NC
Posts: 968
It's probably not his car he's using lol.
Refering to the vid on page 2 of the guy shifting without using the clutch....the one with the white **** on his face.
Refering to the vid on page 2 of the guy shifting without using the clutch....the one with the white **** on his face.
Last edited by White05GT; 01-10-2011 at 06:45 PM.
01-10-2011, 06:59 PM
#25
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
Since synchronizers on modern vehicles are pretty damn good, is there any point to double clutching besides learning how the concept works? I already understand how double clutching reduces the load on the synchronizers and I fully understand how the system works. Besides, I utilize the concept from time to time. But are there any marginal gains of any type if this method is used on a daily basis on regular roads? I wonder if I should utilize this system on a regular basis or down shift the regular old fashioned way. I am looking to get your input as to how you regularly downshift and why? Remember I am only referring to regular road and highway driving and not track driving. Thanks
Only on very low speed downshifts do I get a bit lazy and just kick the gas as I pass the shift lever through the neutral gate.
Even with good, durable synchros, the rotational inertia of the countershaft, input shaft, and clutch disc will require more from the synchros to rev them up if you don't. It's a small thing, but you might as well take the reduced synchro wear benefit that this offers as opposed to throwing it away.
This is NOT related to downshifting in order to slow down as you are approaching a known stop rather than use the brakes, even though the technique that you'd use would be the same.
Norm
Last edited by Norm Peterson; 01-10-2011 at 07:01 PM.
01-10-2011, 07:10 PM
#26
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
Rev matching is putting the engine revs where they need to be in the gear that you are shifting into for the road speed that you're at. Rev-matching actually occurs on most normal upshifts - pretty much automatically when you lift-throttle between gears. But you've got to kick the gas on downshifts since the lower gear requires higher revs than what your current gear has you at. Double clutching makes sure that the clutch disc and the tranny internals that are ahead of the synchro are also rev-matched.
Not using the clutch REQUIRES rev-matching and is a somewhat advanced skill that can come in extremely handy if your clutch linkage becomes inop for any reason. For those who can't double-clutch smoothly and reliably, it's best to forget that this technique even exists.
Norm
Last edited by Norm Peterson; 01-10-2011 at 07:37 PM.
01-10-2011, 07:29 PM
#27
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
It only takes a little practice, and it's easier to do in some cars than others.
Norm
Last edited by Norm Peterson; 01-10-2011 at 07:38 PM.
01-10-2011, 09:46 PM
#29
2nd Gear Member
Thread Starter
Join Date: Jan 2011
Location: Canada
Posts: 303
Double clutching and rev matching will take most or all out of the forward lurch that you can get on downshifts where the revs are up a bit in the higher gear. Why would you not want to learn how to do this? Don't think that your passengers wouldn't notice not having their heads tossed forward. Even if they don't now, they would if they ever get a ride in a MT car driven by somebody who does know how to do these things.
It only takes a little practice, and it's easier to do in some cars than others.
Norm
It only takes a little practice, and it's easier to do in some cars than others.
Norm
I actually know how to do both maneuvers fairly well and do them from time to time, but never seen the need to this since the standard transmission on 05-09 is very good. Its not like i just learned how to drive standard transmission and im certainly not jerky and all over the place. Besides, the majority of the time im in the car alone and im **** about keeping my car clean and i hate people getting my car dirty. Now if you have a solution with this obsessive compulsive behavior, the mike is all yours my friend.
