Auto-X, Road Race, SCCA, NASA, & other motorsports
By civicexracer
#330242 That's great, but it's not necessary since our transmissions are synchronized. And it looks like the guys car in the video has a synchronized trans as well since he does shift without double clutching a couple of times. It would technically be faster and better for him not to double clutch...
User avatar
By panic989
#332459 I hate to bring back a post that seems to have been forgotten about but I'm not much of a tranny guy and had a few questions if someone wouldn't mind answering them for me.

1) What is the point of double clutching? I will admit that I have street raced before but those shifts were all about shifting as fast as possible. It looks like double clutching is just a huge waste of time IMO...

2) Being a synchronized transmission... What does that mean? Is it referring to the synchros that go can go bad? And if it does mean that then what do the synchros actually do?

3) Does double clutching actually do anything for the transmission? Is it less stressful on the gears?
User avatar
By Wicked
#332460 Double clutching is for down shifting not up shifting. It is used to keep the RPM's up high when you drop gears so you don't lose power and keep a nice smooth transition putting less strain on the transmission when going into a turn or otherwise using your gears to slow you down. It is the same thing as rev matching same usage. The only difference is back in the day the syncros in transmission's sucked, You either A couldn't rev match or B it put to much stress on the syncros I don't remember which anymore. So you double clutched allowing you to keep the revs up high by going into neutral and revving before dropping gears. I'm not entirely sure on the syncros, but my educated guess is that they simply synchronize the gears together when you change gears. Think of it as you wouldn't want to change into a gear that is going 0 rpms from a gear that is doing 7500 rpms.

Someone please correct me if I am incorrect.
User avatar
By panic989
#332480 Ok. That makes sense. But why is the guy in the video double clutching in the video. Sometimes he does and sometimes he doesn't.
User avatar
By Wicked
#332490 no idea probably just because he can, could be the transmission hes running, could be a lot of things..
User avatar
By panic989
#332492 Ok. Thanks for the info.
User avatar
By Gustavo
#332722 Synchros are pretty much a Brake it slows down a gear to be able to match the other gear.
User avatar
By Phoenix288
#339279 Isn't it just better to use heal and toe rather than spending some time in the neutral and then shifting down ?
By Canyon Si
#344334 Because he doesn't know how to drive!
By CivicSiRacer
#344650 I'd like to add when autocrossing there is no real need to downshift. Autocrossing is mostly a 2nd gear event. Put it in 2nd and leave it there.
I can probably count on one hand the times I've had to downshift to first in the 17 years I have autocrossed.

Another example I was helping a novice who showed up in his stock S2000. His first run out he was about 15 seconds slower than me (he ran something like a 75 seconds). He came up to me asking how I ran such a good time in a car with 120hp vs his 240hp. So I rode along with him and he would shift for every corner. The course we had had about 30 turns and corners. At 1/2 second per shift per corner that came out to 15 seconds wasted upshifting and downshifting. Next run I told him to leave it in 2nd and just drive. That run came in around 62 seconds. He was amazed :)
By Canyon Si
#344654
CivicSiRacer wrote:I'd like to add when autocrossing there is no real need to downshift. Autocrossing is mostly a 2nd gear event. Put it in 2nd and leave it there.
I can probably count on one hand the times I've had to downshift to first in the 17 years I have autocrossed.

Another example I was helping a novice who showed up in his stock S2000. His first run out he was about 15 seconds slower than me (he ran something like a 75 seconds). He came up to me asking how I ran such a good time in a car with 120hp vs his 240hp. So I rode along with him and he would shift for every corner. The course we had had about 30 turns and corners. At 1/2 second per shift per corner that came out to 15 seconds wasted upshifting and downshifting. Next run I told him to leave it in 2nd and just drive. That run came in around 62 seconds. He was amazed :)


Where do you live?
User avatar
By jred
#344665 Granny shifting, not double-clutching like you should :lol: :lol:

Double-clutching is primarily used by truckers that don't have good synchros on their transmissions or road racers that need to match their transmission speed to the engine speed while downshifting through turns.

I do it when down shifting to save my mounts and match the engine speed so i don't get that "jerking forward feeling". I can't do heel toe...im too tall "foot's too long"