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can anyone explain to me what double clutching means and how one benefits from it. pleae forgive my ignorance but I was also wondering what exactly is toe and heel shifting as well.
 

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Double clutching was necessary back in the days before syncomesh transmissions.

The technique is, at shift time, push the clutch pedal in, move the gear selector to 'N', release the clutch and pat the gas pedal to spin the trans input shaft, depress the clutch again, and move the gear selector to the desired position.

The goal is to exactly match the input and output trans shafts rpms to avoid gear clash (grinding).

I'll leave the toe/heel deal to a subject matter expert. I know what it is but I can't do it. Maybe I'll learn something too.
 

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Roger Ramjet said:
Double clutching was necessary back in the days before syncomesh transmissions.
I've actually found it useful at times. Like when the trans is cold, and isn't wanting to go into gear smoothly. By clutching this way, you can get a smoother shift (its slower though).

One thing though: you blip the throttle when you are downshifting. On the upshift, let the rpms come down so the input shaft is the same (ok, close) speed as the lay shaft (or rather the gears are turning similar speeds).

The upshoot is it doesn't stress the synchros, and your trans will live longer.

Heel-and-toeing is a method of using the brake and gas with your right foot, freeing up the left foot for clutch work. You head into a corner on the brakes with your right foot, and when you need to downshift you touch the throttle with your foot while still braking. That makes the downshift smoother so you don't break the rear tires loose with the shift.

Don't ask me for techniques tho, I suck. Give ol' John Heinricy a call, that dude supposely pulls of clutchless upshifts at full power.
 

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The heel stays on the bottom of the gas and the toe is over on the brake at an angle (I guess it could be done opposite as well... whichever is more comfortable). That way you can be braking at the same time as giving a little gas to change gears (downshifting into turns etc).

ps. I really suck at this as well :) I just know what the technique is
 

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I never double clutch. Always heel and toe on the street just for practice, in preparation for the track. I'm not that proficient at h&t either. I was OK in my LT1 Z28, but now in the S10 it's a whole new ballgame, with the positions of the pedals being so far apart. Can someone explain what clutchless shifting mean and how it works? Do you not depress the clutch pedal at all???:-?

Thanks,
RT
 

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No clutch at all... have to bring revs down to just the right match for speed vs gear vs tach....

From what I understand the 4 second 0-60 time reported for the Z was done by some of the GM guys using this method to save the fraction of time between 1st and 2nd. (not that that was the only way to get 4 sec)

I've never even attempted it :)

I would be interested in what rpm to what gear etc if someone does this in a Z... maybe try it out sometime.
 

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IceSabre said:
No clutch at all... have to bring revs down to just the right match for speed vs gear vs tach....

From what I understand the 4 second 0-60 time reported for the Z was done by some of the GM guys using this method to save the fraction of time between 1st and 2nd. (not that that was the only way to get 4 sec)

I don't believe this. While it is certainly possible to shift without using the clutch, this is not the fastest way to do it. Using the clutch you don't have to wait for the rpm to drop before shifting, while without the clutch you have to wait for the gears to mesh before it will go into gear. I think they achieved their 0-60 times by slipping the s**t out the clutch at launch to keep it hooked up.
 

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I was suspicious as well... I think it was car and driver that I read that in.
 

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Clutchless shifting is done all the time by bike drag racers. The technique uses an ignition kill switch to momentarily relieve the engine torque. Then you brute force the shift.

I suppose you could do something similar by quickly lifting the throttle, shift, and back on the throttle. But I won't be trying it on my car.
 

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I think the clutchless shifting involves the technique of wide open throttle until you are ready to shift and let off the throttle slightly to unload the the gearbox and yank it to the next gear while you are putting the power back into it. Learning some of these techniques wil allow you to drive home when the clutch won't disengage. My 66 Turbo Corvair broke a clutch cable once and I drove it 20 miles home in traffic.

I always double clutch when I down shift! Maybe that's why I got 218,000 miles on the original clutch in a daily driver. I changed it because I thought it was about time, it wasn't down to the rivits yet. I got good at it when I had a 3-speed trans with non syncro first gear and wanted everyone to think I had a four speed in my 53 chevy with a 283.

The heel - toe thing works great in my 62 and I can do it well. I still have not mastered it in the Z06 since the brakes are to sensitive. The 62 has manual full metalic factory brakes and they requrie alot of pedal pressure!
 

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I've shifted my Z without the clutch, its not abusive at all (provided its done properly). Normal shifting does wear the clutch disc, shifting without the clutch doesn't hurt a thing.

And no, you don't floor it, then lift slightly and force it into the next gear. You move the shifter very gently, like the shift knob is an egg, and you ask the trans to go into the next gear, but only when the rpms have matched for that change.

Its a different rpm delta for each gear, and when downshifting you have to increase rpms, and upshifting you have to decrease them.

I agree though, it is a good technique to learn, as someday you might lose the clutch actuation, and need to get home.

Also, I'd bet that they were doing clutchless upshift for the 4sec 0-60. If you're good and can do it fast, the fact that the rpm is matched to the trans speed means zero driveline shock. That also means no wheelspin at the shift - without loss of torque.

Btw, CART cars shift in a similar fashion, except they have the shifters rigged so they drop spark at the shift, eliminating all the torque through the engine/driveline.
 

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Clutchless shifting

A lot of cars use clutchless shifting in road racing. Trans Am cars, etc. While I have not tried it with the Z06 trans, the old Muncies held up well. Under acceleration, you cannot pull the trans out of gear. So, when your revs are nearing the shift point, try pulling the next gear, let up on the gas and the trans will shift to neutral, when the RPM's match the next gear you complete the shift. When you practice it and become proficient, you can make very rapid gear changes.

A variation is the clutch tap. Again rev the engine up to the shift point while pulling on the shifter, let up on the gas and blip the clutch. The pro's make the shift all the time, the rest of us mortals miss a shift 1 in 4 times.

With the trans in the Z06 and all the horsepower you have I would not risk either method. A trans fix will cost you $3000.
 

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Will this technique (specifically the one described by Mike Garfias) work on all cars with manual tranny? I assume that as long as you shift at the correct rpm, then no problem will occur. Now if I'm not at the right rpm, then I can't even pull the shifter out of gear, right? So is there any risk damage I should worry about? I might want to get a econo rental car to practice this. For sure not gonna test it on my Z.:lol:

RT
 

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Oh, 1 more thing: I know the rpm shift point is different for each car, but is it in the low rev range or higher up near the redline?

THanks,
RT
 

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Yes, it will work on all manual transmissions. Heres a few issues tho: the Z has triple synchros, its a lot harder to shift without the clutch on this kinda setup. It is doable tho, you just have to be "right'.

Also, don't worry about getting the car out of gear before the next one, that is the easy step. Getting it into the next gear requires that your engine RPM be right on.

The spread between gears won't change based on where you are in the powerband. For example, 1000rpm between 1st and 2nd, is the same whether you're turning 6000rpm in 1st, or 3000. The drop is always the same. However, doing it at high rpm means there is more force to break the trans - be careful, I refuse to take responsibility for you breaking the trans when you do it wrong :)

I do this fairly often with my Z, if you miss it (and you will while practicing), you'll grind some gear. Just be ready for it, and don't apply too much force and it won't be bad.
 

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mgarfias said:
The spread between gears won't change based on where you are in the powerband. For example, 1000rpm between 1st and 2nd, is the same whether you're turning 6000rpm in 1st, or 3000. The drop is always the same.
Are you saying that the correct rpm for going from 1st to 2nd is 1000 or that it is 1000 less/more than where you shifted out at?
 

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Mike,

You'll have to show me that clutchless upshift technique sometime.
 

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IceSabre said:


Are you saying that the correct rpm for going from 1st to 2nd is 1000 or that it is 1000 less/more than where you shifted out at?
Naw, 1000rpm was a hypothetical example. Off hand I don't remember the RPM drop between 1-2, 2-3, 3-4, 4-5, 5-6

Nor can I remember the gear ratios off hand, which would let me figure it out.

if you have the ratios, you can figure it out this way.

(higher gear ratio)/(lower gear ratio) * (RPM where you shifted out of the lower gear) = (rpm for the next gear)

Here I found the ratios, I'll figure it out for you guys (assuming 3000 rpm shifts.

1st->2nd = 2.07/2.97 = .696 * 3000rpm = 2088rpm
2nd->3rd = 1.43/2.07 = .690 * 3000rpm = 2070rpm
3rd->4th = 1.0/1.43 = .699 * 3000rpm = 2097rpm
4th->5th = .84 / 1.0 = .840 * 3000rpm = 2520rpm
5th->6th = .56 / .84 = .666 (heh, more proof the Z is evil) * 3000 rpm = 1998rpm

Looks like I was about right with the 1000rpm guess (except for 5th)

Hope that helps.

Maule: give me a call Monday or Tuesday afternoon, I'll show you no problem - 505-884-3471
 

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I drove home from from Ohio( 1981) with no clutch with a 327 4 spd chopped 50 Merc. No problem. Even stopped by Niagra Falls on the trip home. Worse part was my friend pushing me back across the border with his 34 Ford. Hardest part was the toll booths and when the starter finally gave out,had to push start in 4th gear.Memories like that just make me appreciate the ZO6 all the more.
Not to change the subject, but you can also use your left foot on the brake and keep the suspension "loaded " while accelerating thru the turn. Haven't tried it wwith the Z yet,maybe the active handling kind of does the same thing.
 

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Baron said:
Not to change the subject, but you can also use your left foot on the brake and keep the suspension "loaded " while accelerating thru the turn. Haven't tried it wwith the Z yet,maybe the active handling kind of does the same thing.
Baron - thats called trailbraking. And I've never had any luck doing it in a car with a manual.

(God I feel like I'm starting to sound like a know-it-all - someone smack me if I really do.)

When you do trail brake, you enter the corner on the brakes, and start to give it some throttle, while tapering off the brakes. You should be at or close to full power as you cross the apex of the corner.

For some history, Mark Donohue is generally credited with this technique... Somehow I doubt he was the first, but he certainly popularized it. He called it the "wheel of life", others call it the "traction circle".

Basically, the theory is that the tire can give X amount of traction in acceleration, whether accelerating, decelerating, or cornering.
However, tires can give X+(some other number) amount of traction because you can corner the tire at .7g (for example PLEASE don't read this as gospel), while decelerating (or accelerating) at .4 or .5g, netting 1.1 or 1.2g.

Ok, that was a REALLY shitty explanation, please go buy yourself a copy of Carroll Smith's Drive to Win or Donohue's The Unfair Advantage (recently rereleased) for much better explanations.

Also, I'm sure of our racer friends here can give us a lot more insight (I've only raced radio control cars, not real ones - but hey, I almost went to Japan last year for the world champs).
 
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