At times when the trans fluid is cold and the car doesn't want to go into first, double clutching helps. This typically only happens on downshifts.

It was only a movie and when were movies realistic? Some so called documentaries are not even realistic. Vin says what he was paid to say because some moron that they call a screenwriter wrote it because they researched it.

 

[QUOTE]Originally posted by tritium_pie
[B]and it isn't as slow as the double-clutch procedure above.

 

If the purpose of double clutching is to save the synchros, what makes it so special to be used on the racetrack?

Do racecars not have synchros, or crappy synchros?

 

true race cars or the older ones don't have synchros. They have straight cut gears and thus the need for double clutching.

 

Ive never seen a complete answer to this either (save the response which refers to getting "everything in sync" when you rev match in "neutral" as opposed to simply with the clutch pedal depressed).

I try and double clutch properly when downshifting, but sometimes emply the "clutch pedal down method" (which the quoted post refers to) because it is just faster.

There is no way engaging and disegaging the clutch twice is as fast as once (and simply rev matching with the pedal depressed).

The other reason it seems faster to me is because ther car seems to "rev" better with the clutch pedal depressed versus in neutral. i.e. it takes a bit less time to match revs (increase rpms) with the pedal depressed then with the car in neutral.

I'm assuming the reason for this is because as an earlier post mentioned you are not actually synchronizing both shafts. But if someone could definitively explain why the pedal in method is not just as effective at preserving the syncros - I'd be interested.

 

[QUOTE]Originally posted by thereisnospoon
[B]Because when you let the clutch out and THEN blip the throttle you are getting everything up to the proper speed (in the gearbox that is) as well as getting the benefits of rev-matching (the clutch doesnt have such a shock when engaging).

 

[QUOTE]Originally posted by tiberius
[B]

This is the explaination I referred to (a good one by the way) - but I'm still not 100% clear on exactly why the quicker method doesnt also preserve the synchros (it does eliminate the lurch).

 

Perfectly explained as always (secretly I was hoping this would coax xviper back into the thread).

Now I am 100% clear thanks.

And as I now understand it, while this statement is true:

It also doesnt do any good either (i.e. doesnt help the synchros).

 

The object of double clutching is to get the input shaft (from engine) and the output shaft (to rear end) to spin at the same speed. All six gears on the input shaft are ALWAYS meshed together with all six gears on the output shaft. The gears on the input shaft however rotate independent of the shaft itself. Dog rings slide on the input shaft to "lock" the gear with the shaft. The synchros smooth this locking operation. A real good place to learn all about this, if you desire, is a site called www.howstuffworks.com. A complete explaination of how a manual transmission works can be found there.

The function of double clutching serves a purpose almost solely for downshifting. You are trying to match the speed of the input shaft to the speed of the output shaft. To do this, you MUST disengage the clucth when you are in the neutral position. When the clutch is engaged, the transmission (input shaft) is not connected to the engine. Double clutching is almost never used in upshifting. It is not needed.

 

[QUOTE]Originally posted by tritium_pie
[B]

I don't think I double-clutch properly, but I do try to rev-match when I'm downshifting.