Question -- What, really, is double clutching, and how do I learn it?

[burbel]

OK, once again, I am feeling like the poor, uneducated, wet behind the ears welp that I am.

What, pray tell, is double clutching, why is it done, and how does one "learn" to do it?

Watching the chase scene in Bullitt, I think I know what it sounds like, but I have no idea how he does it -- now, a Best Motoring Bullitt -- but, alas, I digress...

 

[David]

Brian,

Why - Double clutching is used on down shifts to better align the rpm of each of the (many) moving parts in your transmission. This is especially important in track situations were you are at or near the adhesion limits of your tires because engaging the clutch abruptly at the wrong rpm can jar the tires enough to cause you to lose traction. This is bad.

How - Entering a corner, you have your foot on the brake and push in the clutch. Shift to neutral. Let the clutch out, then (still in neutral) blip the throttle. Since, with the clutch engaged, the motor is driving the input shaft, you now have increased its rpm. The instant after you blip, push in the clutch and shift into the lower gear, before the rpms from the blip fall off. Let the clutch out.

Keep in mind that while this sounds like a long process, the reality is that you just jab at the pedals for each step.

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Don't no nuttin 'bout no NSX;
Don't no nuttin 'bout birthin' no babbies.

 

[Jimbo]

Double-clutching is a downshifting technique where you shift into neutral, release the clutch, bring up the RPMs to match the the lower gear and then you clutch and shift into that lower gear.
http://www.driversedge.com/dblcltch.htm

Like tying shoelaces, it's one of things that is harder to explain than it is to actually do it - or to show someone.

-Jim

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1992 NSX Red/Blk 5 spd #0330
1991 NSX Blk/Blk Auto #3070 (Sold)
1974 Vette 454 4 spd Wht/Blk
Looking for 76-79 Honda Accords

 

[Andrie Hartanto]

With modern transmission, double clutching is not necessary. Skip barber racing school still teaches double clutching, and believe there are some benefit to it. But even Danny Sullivan (the writer of Going Faster, skip barber handbook, CART driver, and more) does not believe in them.

 

[ChopsJazz]

Andrie is right here. The syncros on the NSX, and most modern sports cars, are advanced to the point of making double clutching unnecessary. Many RACE CAR drivers do it because they are using straight-cut gears (the really whiny sounds you hear form on-board footage) and they need to slow down the gears to mesh better. As Andrie mentioned, this is spelled out quite well in the Skip Barber book GOING FASTER.
Heel-toe shifting is a more important skill to master for the reasons listed above.

 

[JoeSchmoe]

Originally posted by ChopsJazz:
Andrie is right here. The syncros on the NSX, and most modern sports cars, are advanced to the point of making double clutching unnecessary.

I partially disagree with the above.

Im not sure if the synchros are just worn, but if Im going at any speed above 15 mph, the gearbox will not go into first at all unless I double clutch. Just matching revs does not seem to help. But, it seems to pop right into first if I double clutch.

I usually double clutch second as well. It slots into gear with little or no resistance.

The synchros seem to be adequate for the rest of the gears.

 

[Edo]

I agree, you are better off learning about/practicing Heel-Toe downshifting as opposed to Double clutching..

Its not very necessary on the NSX.

 

[bartonkt]

Ok, so someone wanna explain how to heel-toe effectively when going into a corner?

 

[burbel]

Well, I noticed that trying to shift into first at, say, 30 mph is dificult, but if I wait a bit (and keep pushing gently), it will slide into first at around 20mph. Could be 15, by this point I'm normally on the brakes.

Where are the Skip Barber schools at? I would love to go, but my job won't give me much time off for another few, oh, months. But I would love to take a couple of days and go through a real driver's training course.

Thanks again for all the replies!

 

[David]

Brian,

The AutoWeek website has a great list of drivers' schools here.

The Skip Barber site is here.

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Don't no nuttin 'bout no NSX;
Don't no nuttin 'bout birthin' no babbies.

[This message has been edited by David (edited 14 August 2001).]

 

[ilya]

Another option and what I am doing is to join a club like NASA and attend their schools. I really wanted to go to a school, but was not ready to pony up 2K for a weekend. Is it worth it? yes. Better than spending that 2K on mods. However, I noticed the HPDEs that NASA runs for $200 a weekend and decided to go that route. Someday I will go to a school like Barber or Bondurant as well. Until then, I can have a NASA instructor with me as I learn. Just another option to consider.

Things like heel toe shifting can become important when you're already skilled and trying to pull tenths off a time. There is so much more to practice and learn before that becomes important IMO.

[This message has been edited by ilya (edited 14 August 2001).]

 

[Andrie Hartanto]

Ilya,

For a reasonable priced driving school, And if u would really learn to drive, I would recommend Driving concepts as they have very good instructors and program.

Other options are local BMWCCA school or PCA school. From my experience, these schools are top notch quality.

Most SCCA organized school are pretty good. U can check their street or high performance school at Thunderhill or Buttonwillow and click on performance driving clinic.

NASA in particular California region, are not selective in getting their instructors. Most instructors are simply not qualified IMO. Some are very good, but because of the way the program run, most of them are not interested in actually teaching u, rather to get free track time.

Fast drivers are not necessarily good instructors.

 

[ilya]

$425 for a weekend is not bad at all. Thanks, I'm definitely going to look into it. Between that and some HPDEs, hopefully I can learn and become comfortable enough to move onto the next level.

 

[Ag NSX]

On the heel-toe subject, I have trouble because my pedals are too far apart and my gas pedal is too far up when I hit the brakes. Anyone have aftermarket pedals that are closer together and would raise the brake pedal slightly? I'd like the aluminum w/holes look.

Kenric

 

[sjs]

Originally posted by burbel:
Well, I noticed that trying to shift into first at, say, 30 mph is dificult, but if I wait a bit (and keep pushing gently), it will slide into first at around 20mph. Could be 15, by this point I'm normally on the brakes.

While you're pressing and waiting, the syncros are screaming.

Perhaps big-buck racers don't worry about what it costs to replace syncros in their street cars. Some similar comments I've heard were actually about down shifting in general. The idea being that the race car brakes were so good and fade-free that "engine braking" from down shifts was irrelevant and represented unnecessary abuse and risk. They just stand on the brakes, and do a single double-clutch downshift into the gear the need for the corner.

I totally disagree with any suggestion that double-clutching is not necessary with today's cars when you are "playing hard" and down shifting at higher revs. Even more true for the NSX which has gears closer to straight cut than most.

If you are just driving casually and down-shifting at low RPM in the lower gear, fine. But if your are racing or just playing hard and down-shifting at higher revs, you better learn to double clutch or your syncros won't last long. Anyone who thinks otherwise probably doesn't understand how they work.

 

[lemansnsx]

Ok, everybody repeat after me:
Gears are for going, brakes are for slowing, gears are for going...

Also, the race schools mostly want you double-clutching to preserve their equipment not because it is essential.

Emerson Fittipaldi was asked about double clutching in one of the race school videos, I forget which one, might have been "Going Faster". (heavy Brazilian accent on) "clutch? sometimes we no uza da clutch".

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The NSX Model List Page

 

[rquintero]

>>bartonkt wrote: Ok, so someone wanna explain how to heel-toe effectively when going into a corner?

Ok folks, how about the more knowledgeable track guys explaining this to both Bartonkt & myself? Surprised no one has dived into this direct question yet. (Andrie / LemansNSX, Mao?)

I do agree that it is unnecessary to double-clutch in just about any street car these days (we do have synchros after all). H&T is good for the plain reason that transmission braking at the track is not only dangerous, but can make you look stupid at the track as well...

Then again at the Skip Barber racing school you *had* to double-clutch & H&T simply because the open wheelers had no synchros.

Actually, what the instructors hammered into my head was "be done shifting before turn in".

But back to the real question: (my) old school is that one is done adjusting at (before) the break line, and entering a corner one is either trail-braking or transitioning into power. Meaning that I got in the desired gear for the turn exit just before or slightly ahead of the turn in point. H&T *after* turn in would be rare at best.

Way open to opinions...

 

[Andrie Hartanto]

Everybody has their own opinion on this. And I totally know how synchro and transmission works. I still stand by my comments before that double clutching is not necessary for modern tranny.

My fellow friend has 3 engine on his car with over 150K miles on the tranny. Never double clutch and has never forced to replae his tranny. This is on a E36 M3.

I would really recommend reading, THE bible of all race car how-to books which is the Carroll Smith "To Win" series, written in this order:

1. Prepare To Win -
All about how to make the race car more reliable, setting up the brakes, suspension, engine, etc.
2. Tune To Win -
How to make your car go faster, now that it finishes the race. Deals with handling questions , plus more esoteric stuff like Ackerman steering and roll couples.
3. Engineer To Win -
Ok, now you want to start modifying your car with fabricated parts to make it go faster.
4. Nuts, Bolts, Fasteners, and Plumbing Handbook (aka Screw to Win) - From the author: "Fasteners and plumbing failures combined are the most common type of mechanical failures in the transportation arena, and if you are involved in high performance automobile or aircraft, a failure can lead directly to you leaving the party early".
5. Drive To Win -
Race car engineering written from the driver's point of view, instead of the crew chief's view like the previous four books. Of course, most of us are both driver and crew chief!

Too bad prepare to win are no longer printed.



[This message has been edited by Andrie Hartanto (edited 16 August 2001).]

 

[nsxtasy]

I still stand by my comments before that double clutching is not necessary for modern tranny.

I stand by Andrie's comments too.

 

[maomaonsx]

Where do you find the time to double clutch on the track when you are diving bombs into a corner? You heel-n-toe as you brake for the turn. Unless you have three legs maybe double clutching would be useful.

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George Wang
Keep it Real!
http://www.geocities.com/maomaonsx/price.html

 

[Lud]

It is true that in a correct double-clutch shift prevents the synchros from having to really do anything. In fact if you just go into neutral, take your foot off the clutch and match revs EXACTLY, you don't even need to touch the clutch to shift back into gear.

However, the whole point of synchros is to prevent you from having to double-clutch. They work extremely well, and unless you are really slamming your shifter around (which you should NEVER do unless maintenance isn't on your tab), there won't be any premature wear. They are doing the job they were designed for.

The amature who does a handful of track events a year really just doesn't need to worry about any marginal increase in wear as long as they don't slam it from gear to gear as fast as they possibly can. If you are competitively racing on a frequent basis and strapped for cash, maybe it is something to consider.

Just doing a quick heel-toe rev match is really all I think most of us need to worry about.

 

[ScienceofSpeed]

Track newbies will have a better time, and learn to drive faster, if they keep shifting to a minimum at first. Practice toe-heel-down shifting on the street, but out on the track, learn the lines then vehicle dynamics, which will lead you quite well into rev matching and toe-heel-downshifting to keep the car settled as your speed increases.

First gear can be engaged by rev matching.

I agree with Andrie. I think sometimes people confuse toe-heel-downshifting and rev-matching with double clutching.

-- Chris

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www.ScienceofSpeed.com - Click for more info
www.NSXClassifieds.com - The internet's only exclusive NSX Classified site!

 

[nsxtasy]

Track newbies will have a better time, and learn to drive faster, if they keep shifting to a minimum at first.

This is EXCELLENT advice.

More specifically - unless you are on a track that has a REALLY REALLY SLOW turn - don't use second gear at all. And don't use fourth unless you have a straight that is so long that you're going to be in it for a ways after upshifting from third at redline.

Once you've learned the line, and you're comfortable with your driving, THEN you can experiment with dropping down to second for the slower turns. But when so many things are new to you, you can eliminate some of the demands on your concentration by staying in third.

 

[sjs]

Somewhere here or on the NSXSC board a guy was just complaining about his 1-2-1 syncro being worn out, AGAIN! My prior comments are especially with regard to that syncro. And note that the originator of this thread said:

"Well, I noticed that trying to shift into first at, say, 30 mph is difficult, but if I wait a bit (and keep pushing gently), it will slide into first at around 20mph. Could be 15, by this point I'm normally on the brakes."

We're (or at least I'm) talking about the lower gears here. If you constantly jam it into first at 30 mph, you will wear out the syncro. It's a friction/wear item, not altogether different than the clutch. It's meant to allow smooth shifting under normal driving. If you don't downshift a lot into first at 30-40 mph, or second at 65-75 then you probably don't need to worry. On the other hand, if you autocross a lot (talk about no time to double clutch!) or enjoy downshifting as you come to a stop while out playing (like me) then it's a different story. Oh well, do as you like, but I've seen enough transmissions with worn syncros in my day (not mine).

And as for not dropping into second at the track, must be a pretty fast track. I've tried coming out of 50-60 mph turns in third with a stock NSX and it was horrible.

 

[nsxtasy]

And as for not dropping into second at the track, must be a pretty fast track. I've tried coming out of 50-60 mph turns in third with a stock NSX and it was horrible.

You are forgetting what it is like to be a beginner on the track - worrying about the line (what's the line, again?), worrying about your brakes, nervous as heck, eager to get more track time, trying to pay attention to the guy next to you who keeps telling you what to do differently, thinking about how you messed up the turn three turns ago instead of the one that's coming up, ... you get the idea now? In those circumstances, reducing one of the biggest demands on your concentration will improve your lap times far more than gaining a few tenths of a second exiting a turn. (And remember, you also lose a good half second of power with every upshift and every downshift.)

This is why instructors are paid the big bucks (yeah, right

) - to keep in mind what it's like to be a student, and to improve by having the student work on one driving element at a time, instead of trying to do everything right the first time out and getting totally overwhelmed and doing nothing right instead.