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Old 8th November 2001, 13:15   #31
ijam
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Thanks for taking the time to do the videos Greg, and Greg/Johann thats one of the great discussions that make this board so good.

Interesting point about accelerating the engine vs slowing it. I've never had trouble with ensuring the clutch is fully engaged before reving on up-shifts - a consequence of having always driven manual cars maybe.

As greg says, up-shifts can be extremely fast even when allowing the clutch to grab fully. One thing I do which I hope doesn't harm the clutch or transmission is take the car out of gear as my foot is travelling downwards - say 15% of pedal travel. depending on the gear change in progress, I sometimes put the next gear in on about 60% of clutch pedal travel and so can get back off the clutch faster (ie its not fully depressed)

I try to be careful with that though as obviously too little clutch travel will result in bad noises (not in my M5 yet... but I've done it once or twice in previous cars)

Back to accelerating the engine with the clutch - if you're right greg thats good news. The area I do have trouble with is rev matching down shifts smoothly (in fact I generally do as johann describes but slower, except when driving hard I don't like to have the clutch disengaged while cornering). From what you say, theres not much chance of damage to the clutch even if you don't try and rev match and just let the clutch straight up after a down shift?

ciao

Ian
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Old 8th November 2001, 13:45   #32
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Let's say you're braking before a corner.
If you are smooth with your downshifts and wait until the speed has dropped enough, i.e in the later part of the braking, you can let go of your clutch smooth. If you do it too quick your rear end may be upset.

So if you come roaring down a straight in 200km/h, you start to brake, let the speed go down enough and in the end of the braking you de-clucth and choose the gear your going to use when entering the corner let go smooth of the clutch. When you let go off the brakes you are all set for entering the corner.

It is important that you let the speed down enough so you don't release the clutch before your speed has decreased enough. This will wear your clutch and if the speed is to high you will blow your engine with or without heal-and-too.

Sometimes it can be useful to release the clutch abrupt just when entering a really tight corner to get the rear out, though.

However, Rev matching, wheter used with heal-and-toe or not, WILL when performed properly wear your clutch less.

In basic race traning the procedure is:

* Start braking

* Just before entering the corner release the brakes

* Downshift either with rev matching or releasing the clutch smooth.

* Give a little throttle and entering the corner accelerating just a tiny bit.

This method should work fine in normal traffc since you shouldn't need the extra time for braking that heal-and-toe provides.

Rev matching without heal-and-toe is much easier to learn.
Perfect time for practicing this is when downshifting to overtake.

When you can do this properly, you can start practicing heal-adn-toe but don't use it in traffic to give you an extra .5s for braking.
Do it when you have the marigin on your side.

Like Greg says once you know it''s not that hard.

And the keyword is SMOOTH.

Cheers,
/Johan
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Old 8th November 2001, 13:54   #33
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this is some great info here.. I was thinking maybe we should start a new forum on driving techniques?
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Old 8th November 2001, 17:21   #34
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ijam:

re: "One thing I do which I hope doesn't harm the clutch or transmission is take the car out of gear as my foot is travelling downwards - say 15% of pedal travel. "

This is OK if your timing is right. I do it too - the M5 seems to tolerate it pretty well. If the lever slips into neutral smoothly, there is no load on the gears and you're doing it right. Ususally this means you have the throttle "feathered" - i.e., just enough to keep the engine at the car's speed. Some transmissions are harder than others in this regard. I find it is extremely difficult to get the Porsche into neutral during a shift when the pedal isn't all the way in - you can feel it knock just a bit. This knocking WILL wear your synchros a bit - although it will wear them on the deceleration-load side. This means you probably won't adversely affect upshifts or holding gear under acceleration, but you might start having more trouble with downshifts or popping out of gear on deceleration.


re: "From what you say, theres not much chance of damage to the clutch even if you don't try and rev match and just let the clutch straight up after a down shift? "

Right. Obviously, any slip is wearing the clutch, just like any braking wears the brakes. But slip alone isn't what causes a clutch to fail prematurely - it is heat from the slip. Heat buildup comes from the amount of power transferred in slip mode. Merely accelerating (or decelerating) the engine's rotating mass requires much less energy than asking the clutch to fight the engine's power at anywhere near full throttle.

In other words, if you let slip accelerate/decelerate the engine while your foot is off the throttle - it isn't a huge deal.

Of course, the more accel/decel required, the more wear, the longer or potentially jerkier the shift will be. This is why you should TRY to rev-match. Even if you don't get it exactly right, you are only asking the clutch to make up for, say, a 300 RPM difference instead of a 2500RPM one.
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Last edited by greg; 8th November 2001 at 18:41.
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Old 8th November 2001, 18:21   #35
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thanks Greg

incidentally I've noticed that changing into neutral is easiest when you're not quite fully off the accelerator and still have a bit of momentum (which of course makes sense since all the gubbins are rotating at the same speed and the wheels haven't started to slow yet) - comes down to timing again

ciao

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