Will double clutching when it's cold out help save my synchros? Should I ALWAYS double clutch? What purpose does this serve when auto-xing?
Just wondering!
Later,

 

Double-clutching, when done properly, will always save your synchros.

The purpose of synchros is to match the transmission input shaft speed to the output shaft speed, or "rev-match," before engaging the gear. So, every time you shift, the synchro on the gear being selected wears slightly.

The purpose of double-clutching is to use the engine to do the same job as the synchros. If you rev-match the engine to the transmission before selecting the gear, the synchro does very little to no work. In transmissions without synchros, aka "Crash boxes" double clutching is the only way not to beat the crap out of the gears.

In autox, you would have rapid, high-rpm shifts. These are the hardest on your synchros. So, by double clutching, you would aid the synchros.

However, it's tricky to get good at, especially at the speeds and cornering situations you find yourself in while autoxing. If you want to get good at it, do it all the time.

 

"Will double clutching when it's cold out help save my synchros? "
umm.. it seems like it might.

"Should I ALWAYS double clutch?"
I would say no, unless you get a stiffy from it. It is a bit more wear on your throw-out bearing, etc. The synchros do a fine job most of the time.

"What purpose does this serve when auto-xing?"
In Autocross you want to be smooth. If you can do it really well, it is probably the smoothest way to get into first gear (from second) if you get _really_ slowed down by a painful corner. Most of the time it just ends up costing you time. Of course, if you accept that you're willing to sacrifice some tenths to hope to learn to one day be able to double clutch super-smoothly.. up to you.

my observations, not necessarily truth.

 

Thanks!
I'm teaching myself to rev-matching on the downshifts, which is a little more difficult than double clutching. I guess d/c-ing as quickly as just throwing from one gear to the next is the trick, huh?
Any tips for a beginner?


[Modified by chairmankaga, 5:16 PM 11/14/2001]

 

how can you double clutch without rev matching? You aren't talking Fast&Furious double clutching, are you? As I have heard from people who saw that movie, they said double clutching when they meant slipping the clutch.

I'm confused.

 

OK, maybe I'm confused.
I thought double clutching was this - clutch in, shift to neutral, clutch out, wait for revs to fall to where you'd expect on the upshift, clutch in, upshift, clutch out and accelerate.
And rev matching was this - clutch in, blip throttle to bring revs up to where you'd expect them to be on a downshift, downshift, clutch out and accelerate.
Either way, they're both basically rev matching, when you get down to brass tacks. One is matching up, the other is matching down.
Correct me if I'm wrong?
In either case, any tips would be appreciated. I'm running a short auto-x on Dec. 2.
And while we're on the topic, what exactly IS slipping the clutch? I've heard so many definitions I really have no idea!


[Modified by chairmankaga, 7:22 PM 11/14/2001]

 

dont need to doubleclutch.. just learn how to shift better!

 

I'm tryin'! Oh Lord, how I'm tryin'!
It's amazing... I've been driving a manual since I was 16, and I'm still learning how to do it right.
I wonder if there's some great online tutorial? Racing techniques or whatnot? Whatever... I'm doing the SCCA school in the spring, so that'll help.
This whole double clutching thing is a mess. I found some info at an old-school british roadster racing site. Yes, the true definition of double clutching is as I stated above. What it seems everyone here is talking about is rev-matching, which has absolutely nothing to do with double clutching, other than both are done to match tranny to shaft.
Right?

 

I rev match a little when downshifting to slow down.. my car drops the revvs to quckly if I try it the normal way, so i save the harsh clutch engaugment by doing it..

when racing.. i just shift really fast at the same time.. taking my time to do it right the first time.. I have lost a couple races by missing a shift... which sucks.. i learned to slow down and do it right the first time..

 

I'm sorry I related the two (double clutching and rev matching.) I was referring to double-clutching.

What double clutching does is use the clutch to match the RPMs of the input shaft of the transmission to the RPMs of the output shaft, keeping the synchros from doing the work. That's what I meant by rev-matching.

Rev matching the engine is matching the engine RPM with the new gear's transmission rpm. This saves clutch lining, as you're not asking the clutch disc to accelerate the engine or decelerate the vehicle. It also saves your passengers their lunch!

 

Always rev match because there's no way to drive smoothly without doing it.

I double-clutch when I'm downshifting 2 or more gears at a time, or when downshifting to 1st from a roll. Downshifting 1 gear, I don't bother because the shafts speeds are close enough for the synchros to easily deal with. Upshifting 1 gear at a time, I don't do anything special. When upshifting more than 1 gear at a time, I also double-clutch, or just gently push the lever in.

Anyways, it's all about being smooth. Minimize the jerks, push the shifter gently with your fingers and not your hand. If you feel a jerk, that means your transmission just took a jerk. If the shifter will only go in with a lot of effort, you're crunching your synchros.

 

Thanks for clarifying, guys. I'm sure I'll be getting schooled on all theis when I get whupped in a couple of weeks by guys who've been driving competetively for longer than I've been alive!
Honestly, I can't wait!

 

Do we have an agreed definition of what exactly 'clutch-slipping" is yet? Now you guys have got me interested in this. And how healthy is it to shift w/out using the clutch at all?? I've got some friends that swear by it, and that you never grind if you throw it fast enough. Seems kinda risky to me, but I was gonna see if I could get some other opinions.

 

sorry for my lapse in monitoring this thread.

Chairmankaga: It is exceedingly rare for someone with a moderately healthy car to double clutch on upshift. Double clutching on downshift is what I was expecting you to be refering to. As such, it's pretty dang hard to double clutch smoothly on a downshift without rev matching.

 

So basically, downshifting WITHOUT double clutching and rev matching is just good ol' trucker engine braking?
So when you rev match, do you have to double clutch and rev while in neutral, or can you match with the clutch in while in between gears? From what I can gather from other related posts, double clutching (meaning, clutch in, neutral, clutch out, clutch in, shift, clutch out and accelerate) and revving while in neutral actually might be the opposite of what you'd want to do on a downshift because it inherently takes more time, causing you to lose revs when you actually want to gain them.
Maybe I should ask our local autocross guru next time I see him...
Regardless, this is a pretty good discussion. It seems a lot of people might have all of these techniques mixed up.
We should compile a book of HOnda/Acura race driving techniques. Who's up for that?


[Modified by chairmankaga, 3:10 PM 11/16/2001]

 

Downshifting without rev matching is just called unsmooth driving. Let the clutch out slowly and it'll be a bit more smooth, but you'll still be burning lots of clutch. Let the clutch out quickly and you'll get a huge jerk.

It's ok to rev match without double clutching, but it's just a little harder on the synchros. For instance, say you're going 50mph in 5th gear 2500RPM. If you want to downshift to 2 as quickly as possible, step on the clutch and DON'T release the throttle. While you're moving your shift lever from 5 to 2, your RPM's will rise because your foot is still on the throttle. By the time your shift lever is in 2, hopefully your RPM's will be matched to something like 6000RPM. Then you can let out the clutch.

To downshift from 5 to 2 with minimal wear on the synchros: clutch in, neutral, clutch out, blip throttle to whatever matches, clutch in, gear in, clutch out.

 

Isn't what you described kind of like reverse power shifting?
I think where things got confused was that I saw a post on auto-xing that stated you must learn to double clutch. I knew the definition of double clutching as the old school upshift without synchro method (my dad's a Brit roadster freak, so I pretty much knew what it meant anyway), not the modern downshift and rev match method.
Last post helped! I might as well learn to do it right. Homework for the weekend!

 

Guys, double clutching is what you should do when you downshift and involvles rev matching. There is no point to double clutch without matching the revs. It would be the same as the basic clutch in, shift, clutch out. you don't need to do it when you shift unless you leave the clutch in for a while or something. the revs bascially line up when you shift anyway if you time it right. double clutching if done right and practiced is, in my opinion, quicker than regular downshifting w/o rev matching. you can get the power to the ground quicker even though the action of putting the shifter into gear my take a little longer when you double clutch. the idea behind that is that when you don't rev match or anything the car takes time to get the power to the wheels becuase the engine and tranny speeds have to match and the synchros are working. but if you match then the synchros don't have anything they need to do and the speeds are matched and the power goes straight to the wheels. double clutching is pretty easy and becomes second nature if you practice it all the time.

 

Lurk in the competition forum.

Umm.. First off, I'm not sure I understand what you are talking about with losing revs while revving in neutral. Secondly, you generally want to do your double clutching or rev matching in your braking zone, so the braking (or at least not accelerating) continues after your downshift until you've hit your apex.