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

[ChopsJazz]

In my opinion, proper heel-toe shifting is not something that should be limited to track use, but should be practiced often and used during any "spirited" drive.
You are all correct in advising to build slowly at the track, as it can be, as you've all said, quite overwhelming. However, heel-toe shifting is a pretty important skill to learn to help maintain balance during the entry/exit of corners.
To wit: When entering a corner at 100 mph in 4th gear, knowing that your exit speed will be 70 mph, it would benefit the NSX driver to downshift at some point in the corner to 3rd gear to put the engine in a more powerful rev range (don't want to lug around in 4th at 70! I mean, our VTEC isn't THAT great). At these speeds if the downshift were to take place without blipping the throttle to match revs in the lower gear (3rd) the car would lurch forward on its front tires drastically upsetting the balance of the car (think back, we've all done this). If the balance is upset in this manner at any point in the turn, this would most likely result in a spin at these speeds.
The answer is to, while braking and with the clutch in, rotate your foot over to the gas pedal to blip the throttle. This will bring the engine up to the rpm range that it will be spinning at if you drop down a gear. Downshift now and the engine smoothly takes up the lower gear and your precious NSX stays balanced and on the pavement where it belongs.
Some people have mentioned that the stock NSX gas pedal is too far away to do this easily. I found this to be true, and bolted on a set of Momo's. With these I simply have to slip my right foot sideways a bit instead of truly Heel-Toeing. But if you have stock pedals, it can still be done. If you have seen any of the popular NSX vids with in car cameras, you'll see the drivers actually twist their foot around to hit the gas with their heel.
Mind you, this is difficult to do so as not to pump the brake when you blip and unbalance the car with the brakes. And it should be practiced slowly. Like in your garage. But it will pay dividends when mastered by helping to get your car in the right gear for the best exit speed and let you stay in balance through it all.
Sorry for the long post.

 

[Edo]

In my opinion, Heel-toe braking is absolutely *essential* to driving at the track. I attended the Bondurant School of racing, and the first 2-3 hours of the first day you are there is spent mastering the heel toe downshift. If it werent so necessary at first, then why is it the absolute first thing they teach to newbies?
I think that it is one of the most beneficial things to learn to do.

 

[Lud]

Originally posted by sjs:
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. ...[cut]... 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.

You are absolutely right. If you constantly "jam it into first at 30 mph," you will indeed wear the synchro out. You will wear it out because you are misusing the car two different ways:

1. You should never, ever "jam" it into any gear. And there isn't even anything to gain by downshifting quickly. If you feel you need to rush a downshift, you have done something else wrong. Downshifts should always be fairly leisurely. Nobody ever won a race with fast downshifting.

2. You should not downshift into 1st at 30 mph. If you are downshifting to first at your example speeds of 40 or second at 75, you are driving incorrectly. There is simply no reason to downshift when doing so will put you so close to redline in a very short gear like first or even second. You will only lose time.

In fact I have never been on a track where anyone I talked to used 1st gear other than to get going. The only time I really ever use first gear even on the street is to get going.

If you drive correctly the synchros work fine. Just because someone else managed to wear their synchros doesn't mean you shouldn't use them. How do we know they know how to drive, or the previous owner of their car knew how to drive if it's used?

Oh well, do as you like, but I've seen enough transmissions with worn syncros in my day (not mine).

I've never had to replace synchros in any car I've owned (several driven past 100k miles) and I almost never double clutch. I've never worn out a clutch either. I agree many people do wear their synchros prematurely, but I contend that premature wear is due to misuse.

Of course that's just my opinion; as you said, it's your car drive it as you please! Double clutching can be fun. And yes, it WILL reduce wear on your synchros, but I think the different is negligable if they are used properly.

[This message has been edited by Lud (edited 17 August 2001).]

 

[nsxtasy]

When entering a corner at 100 mph in 4th gear, knowing that your exit speed will be 70 mph, it would benefit the NSX driver to downshift at some point in the corner to 3rd gear

If you are entering a corner at 100 mph, you never should have upshifted to fourth gear in the first place.

The only time I really ever use first gear even on the street is to get going.

I use it when exiting one of those parking garages where all the rows are sloped.

 

[sjs]

Originally posted by Lud:
I've never had to replace synchros in any car I've owned (several driven past 100k miles) and I almost never double clutch. I've never worn out a clutch either.

Nor have I except when I bought an old car that already had the problem, but I double clutch into second virtually all the time out of habit. Not much into first since I quit autocrossing nearly 20 years ago, but got bloody good at it then because my first car had none when I got it.

I agree many people do wear their synchros prematurely, but I contend that premature wear is due to misuse.

Obviously, which is exactly what the quotes I used above described. Perhaps you don't realize how many people push into a lower gear at speeds that constitute misuse. ("jam" may have been to harsh a term for many of them, but doesn't change my point.) Same guys who side-step the clutch at 4k every chance they get then complain the stock clutch is weak. Jillions of them out there.

When entering a corner at 100 mph in 4th gear, knowing that your exit speed will be 70 mph, it would benefit the NSX driver to downshift at some point in the corner to 3rd gear to put the engine in a more powerful rev range (don't want to lug around in 4th at 70! I mean, our VTEC isn't THAT great). At these
speeds if the downshift were to take place without blipping the throttle to match revs in the lower gear (3rd) the car would lurch forward on its front tires drastically upsetting the balance of the car (think back, we've all done this). If the balance is upset in this manner at any point in the turn, this would most likely result in a spin at these speeds.

Personally, I avoid shifting in the middle of a turn, and downshifting without matching revs isn't really like lurching forwards. What you get is sudden braking from the engine, so I guess it's more like lurching backwards if anything. Either way, you're certainly correct about it upsetting the balance of the car in a turn.

 

[QWKSLVR]

David & Ken (Chopsjazz), just when I thought I had mastered double clutching as described by Ken, whereby when braking, I step the clutch in, shift neutral and w/ the clutch still in, I blip the gas & downshift, I read in David's post near the top, where he says to shift in neutral, lay off the clutch and then blip the gas, then downshift--which is the right way? It's a lot easier to keep the clutch in as Ken says, but is this detrimental to the clutch as I'm simultaneously blipping on the gas just for that instant?

 

[QWKSLVR]

David & Ken (Chopsjazz), just when I thought I had mastered double clutching as described by Ken, whereby when braking, I step the clutch in, shift neutral and w/ the clutch still in, I blip the gas & downshift, I read in David's post near the top, where he says to shift in neutral, lay off the clutch and then blip the gas, then downshift--which is the right way? It's a lot easier to keep the clutch in as Ken says, but is this detrimental to the clutch as I'm simultaneously blipping on the gas just for that instant?

 

[Lud]

Double clutching, by definition, means you clutching twice during the shift. Clutch once and shift to neutral, release clutch and blip throttle, clutch again and shift into gear.

If you keep the clutch depressed the entire time and blip the throttle to match revs, you are not double clucthing, you are simply rev matching.

 

[Lud]

sjs - You are right, a LOT of people unknowingly misuse their clutches and transmissions. But I do not think the solution should be to tell everyone to double clutch their shifts - instead I think it would be better to teach them how to shift properly :-D

Again just my opinion!

 

[apeltier]

I agree with the heel and toe guys. Double clutching, while it accomplishes the same thing, is too cumbersome. There is just too much going on to do this effectively and be fast.

Heel and toe is harder to learn, but much faster to use once mastered. I also agree that you can learn to heel and toe on the street. Just don't do it around other traffic.

I learned in my GSR which is pretty easy. The NSX is a little harder, but I'm coming along okay. I've not mastered it in either car. Motorcyclists do it all the time. Its funny but I've always had trouble on my bike doing it without screwing up. Watch any GP500 or Superbike race and you'll quickly realize the benefits of matching revs while downshifting under hard braking. Its really amazing.

I also agree that track time is usually so limited there are more important things to spend your time on, but I've never taken my car on the track so I'm really just talking out of my butt here.

Alan


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[sjs]

Originally posted by apeltier:
... Heel and toe is harder to learn, but much faster to use once mastered. I also agree that you can learn to heel and toe on the street. Just don't do it around other traffic. ...

They need not be mutually exclusive. You can easily heel & toe + double clutch at the same time. I guess I've been doing it so long that it never occurred to me that people found it difficult. I rarely shift from 3rd - 2nd without double clutching, even when commuting to/from work. Perhaps people don't realize that the first dip is very quick and slight, just enough to slip the trans out of gear. Then the throttle blip is the same as you do anyway for rev matching, except that it also syncs up the trany parts. The whole thing happens in the blink of an eye when you get to the point where you do it completely without thought. In my mind, that is shifting properly.

[This message has been edited by sjs (edited 18 August 2001).]

 

[GMat]

Originally posted by rquintero:


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

I would tend to agree with LeMans as they tell you this to preserve the equipment. I vintage race a Ginetta G-12 with straight cut gears (same as the Formula Dodges you use at Barber) and i hardly ever use the clutch. Just for downshifts and if you blip the throttle properly you dont even need to use it then.

 

[lemansnsx]

Originally posted by GMat:
I would tend to agree with LeMans as they tell you this to preserve the equipment. I vintage race a Ginetta G-12 with straight cut gears (same as the Formula Dodges you use at Barber) and i hardly ever use the clutch. Just for downshifts and if you blip the throttle properly you dont even need to use it then.

Agreed!
Seems like a lot of people here have some real misconceptions of what constitutes good driving technique! Shifting in the middle of a corner - indeed!

Also - blipping the throttle with the clutch depressed does nothing for the transmission - you're not "rev matching" - you're really not accomplishing much of anything - remember you are trying to match the speed (rpm) of the engine with the speed of the gear train. To do this you must bring the rotating parts of the gearbox up to the same speed of the engine. To bring the transmission up to speed the gear train must be driven by the engine therefore the clutch must be released hence the complex to explain but sheer poetry when properly done activity known as double clutching. Got it?
Repeat after me: gears are for going, brakes are for slowing...
PS: in case anyone doesn't understand why shifting in the middle of a corner is a bad thing - when the car is not being "driven" - that is, when the rear wheels are not braking or accelerating - the car is, inherently, unbalanced and, therefore, unstable. Don't believe me? Go spend some of your modification budget where it will do the most good - on a 3 day Skip Barber school.

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[hejo]

Originally posted by lemansnsx:
Seems like a lot of people here have some real misconceptions of what constitutes good driving technique! Shifting in the middle of a corner - indeed! :{

Wow! I was traveling for a week and just got back.

Q: What is double clutching?
A: I think David explained double clutching correctly.

Q: Should you need to use it with the NSX?
No.

Here are my thoughts on the subjects:

1. Learn to heel toe.
2. Learn how to drive the correct lines, entering at the appropriate speed in order to exit at the optimal speed. Be smooth.
3. As lemansnsx said: Gears are for going, brakes are for slowing.
4. Downshifting in the middle of a corner is usually a bad thing - rev mismatch causes tires to lose traction - spin out. The same thing can occur in upshifting as too much power can cause tires to spin - car spins out.

The key to going fast is being smooth.

 

[NSXLNT]

Is proper heel/toe done with toe on brake pedal and heel on gas pedal, or the other way around?

 

[lemansnsx]

Originally posted by NSXLNT:
Is proper heel/toe done with toe on brake pedal and heel on gas pedal, or the other way around?

Depends on the car - pedal placement - height of the two pedals and the distance between them, the shoes you are wearing, personal preference, etc.
Traditionally it's heel on brake, toes angled over to give the old "whunnnga" on the gas. In some cars it isn't really heel/toe at all. It's more like side of foot, other side of foot and a roll of the ankle.


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[Lud]

Originally posted by lemansnsx:
Also - blipping the throttle with the clutch depressed does nothing for the transmission - you're not "rev matching" - you're really not accomplishing much of anything -

You're right, it doesn't do anything to the transmission, but it does make a difference because you are spinning up the engine. It's not as big a difference as rev matching while double clutching since the input shaft is disconnected from the tranny, but it is still very noticable. If you don't rev the engine, you will be forcing the rear tires to spin the engine up from 1000 RPM to whatever RPM the gear you selected dictates. If you blip the throttle without double clutching then all the rear tires have to spin up is the transmission, not the transmission AND engine.

[This message has been edited by Lud (edited 19 August 2001).]

 

[nsxtasy]

Originally posted by lemansnsx:
blipping the throttle with the clutch depressed does nothing for the transmission - you're not "rev matching"

When I first read this, I found it confusing. If I'm downshifting (without double-clutching), I press the clutch, then hit the throttle, so that the revs increase to match the road speed of the car in the lower gear, before letting the clutch out. I don't understand why this is not "rev matching".

 

[lemansnsx]

Originally posted by nsxtasy:
When I first read this, I found it confusing. If I'm downshifting (without double-clutching), I press the clutch, then hit the throttle, so that the revs increase to match the road speed of the car in the lower gear, before letting the clutch out. I don't understand why this is not "rev matching".

You get partial credit for matching the engine rpm to the correct "speed" for the lower gear but you really need to bring the transmission up to the same rpm.



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[ChopsJazz]

nsxtasy,
Why can't I enter a corner at 100 mph in 4th gear? My short gears and 4,23 R&P bring me up to about 125 mph. In my experience on the track, you don't necessarily have to wind out the engine in every gear as I enjoy the torque of the NSX on sweeper corners. Like the "Taledega" 80-85 mph corner at Buttonwillow. That is a great corner to enter and exit (at 90-100mph) in 4th gear.
You sound a little rude to imply that I "should never have upshifted in the first place". Give me a break!

 

[nsxtasy]

I was assuming that, like most track drivers, you would want the fastest lap times and fastest acceleration. We had been discussing the example you previously gave, for a turn where you were entering at 100 mph and exiting at 70 mph.

Since braking should normally be done before you are actually in the turn, it was logical to assume that you were referring to a turn where you were entering the braking zone at 100 mph, braking to 70 mph, and entering and exiting the turn at 70 mph.

For fastest lap times and fastest acceleration, the general rule with the NSX is to stay in the lowest gear possible, shifting at or close to redline. With any of the stock sets of gears, you can stay in third gear over 100 mph, and for fastest lap times, you would not want to upshift to fourth in this example.

Even with the short gears and 4.23 R&P that you had not previously mentioned, your third gear is good to 97 mph. In your 100 -> 70 mph example, you will still probably have faster lap times leaving it at redline in third as you're approaching the end of the straight, instead of upshifting to fourth for that last 3 mph of speed.

Obviously, you CAN upshift to fourth gear or even fifth gear if you want to. It just won't be the fastest way around the track. And most people are looking for the fastest times when they're on the track.

That is a great corner to enter and exit (at 90-100mph) in 4th gear.

Aha! Now you are changing the example. Remember, the example you previously gave - the situation we were discussing - was for a turn where you were exiting at 70 mph. In this new, different example, a turn where you are going 100 mph after the braking zone, then you are correct, it would make sense to be in fourth gear in that turn with your gearing. That would be equally true of anyone with the NSX six-speed or the short gears (with stock R&P). Those with the stock five-speed might benefit from third gear, since that would provide another 15 mph of acceleration before the need to upshift to fourth.

You sound a little rude to imply that I "should never have upshifted in the first place". Give me a break!

And you seem to be overreacting. My response was appropriate for the example that you first gave. I don't think it's fair to change the example being discussed and then get upset about an earlier response made under a different set of assumptions.

If we fully discuss and understand the two different situations being used, we can realize that they can give us two different answers. And hopefully, we can do so amicably, too.

 

[ChopsJazz]

Well, then try this example:
When running up the hill toward the Cork Screw at Laguna Seca, in an effort to maximize my speed into the braking area, I run out 3rd and shift to 4th and stay hard on the throttle for about 1 second before heel/toe braking and downshifting into 2nd gear for the downhill.
In my opinion, I have all the "business" I want to be in 4th at 100 mph.

 

[nsxtasy]

The benefit of one second of acceleration is debatable, but it's possible that you might save a fraction of a second by doing so with your car's gearing.

However, at the time the original example was suggested, there was no mention of aftermarket gearing. And it's a simple fact that any NSX with stock gearing (or even with short gears and the stock R&P) - but not your gearing - wouldn't be upshifting to fourth gear for fastest lap times in the original example, entering a braking zone at 100 mph.

No need to get so upset about it, though...

 

[lemansnsx]

Originally posted by ChopsJazz:
Well, then try this example:
When running up the hill toward the Cork Screw at Laguna Seca, in an effort to maximize my speed into the braking area, I run out 3rd and shift to 4th and stay hard on the throttle for about 1 second before heel/toe braking and downshifting into 2nd gear for the downhill.
In my opinion, I have all the "business" I want to be in 4th at 100 mph.

You are probably losing more time with that last upshift than you are gaining - using the duration in your example.



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[Andrie Hartanto]

Originally posted by sjs:
They need not be mutually exclusive. You can easily heel & toe + double clutch at the same time. I guess I've been doing it so long that it never occurred to me that people found it difficult. I rarely shift from 3rd - 2nd without double clutching, even when commuting to/from work. Perhaps people don't realize that the first dip is very quick and slight, just enough to slip the trans out of gear. Then the throttle blip is the same as you do anyway for rev matching, except that it also syncs up the trany parts. The whole thing happens in the blink of an eye when you get to the point where you do it completely without thought. In my mind, that is shifting properly.

From Drive to Win by Carroll Smith:
"Many authors (or maybe translators) who should know better recommend double clutching in the racing car - I'll be damned if I know why. I do not know of one racing driver who double clutches - either up or down. Some of the older vintage cars require it, but that's not what we are talking about here" (2-43) Chapter 6.

He goes into details on transmission among other things. And why modern tranny doesn't need one. Even racing cars with dog engagement.

Danny Sullivan, writer of Going Faster (SkipBarber handbook) also said that he never double clutch and never see the need to do so, even though he teaches them at school.

I strongly suggest people who is serious about driving to read his books. At least Drive to Win, as the older ones sometimes don't apply anymore. His writing style is very attractive to me, and I really enjoy reading his books. Lots of diagram and picture to accompany so u understand better. Carroll Smith is an engineer with experience in team manager, engineer and driver.



[This message has been edited by Andrie Hartanto (edited 30 August 2001).]