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Double clutching isn't just double pressing Posted by Ari [Email]  (#2847) [Profile/Gallery]
(more from Ari) on Fri, 12 Sep 2008 17:45:02
In Reply to: art of shifting, rc3saabs, Fri, 12 Sep 2008 13:27:44 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Double clutching isn't just pressing the clutch pedal twice. Say you're downshifting. In double clutching, you depress the clutch pedal and shift out of gear. You then release the gas pedal in neutral. You then press the gas pedal and bring up the engine revs to where the engine would be (higher revs) in the gear you're going to shift into. Then press the clutch again, move the shifter to the lower gear, and release the pedal.
To get the revs up when downshifting and if you're braking, you keep your right toe/ball of the foot on the brake, and swing your heel over to blip the gas. Hence, "Heel and toe".
When upshifting, you let the engine revs drop to the lower engine speed of the higher gear.
For a transmission to shift smoothly, the internal gears need to be going at the same speed in order to mesh when the shifter moves. In a modern syncromesh transmission, there are syncros, which bring the shafts and gears up to speed. Syncros slightly slow down shifting, and they can wear out over time. If you just try and jam the shifter into place, the synchros have to work hard to get the gears up to speed, and things bind.
When you double clutch, that time in neutral you use the engine to make the intermediate shaft speed the same as the drive gears, and things move smoothly into place - you're doing the job of the syncros. Do it right, and it's a beautiful thing. Do it wrong, and things sound awful.
Why double-clutch? It's a critical skill for non-syncromesh transmissions, like you'll find on race cars. Done right, you can shift faster in a non-s.m. tranny, and fewer parts are less to break in the tranny. Done right, it can make a syncromesh tranny shift nicely.
If you're simply pressing the clutch pedal twice, and not matching engine speed to the new gear speed while in the neutral phase, it WILL shift smoother. That's because you're giving the syncros longer to do their work. But it isn't double-clutching.
posted by 76.227.247...
, Fri, 12 Sep 2008 17:45:02 <-- Viewing This Message
, Fri, 12 Sep 2008 16:05:21
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