[QUOTE=captain_pants,Dec 2 2007, 08:20 PM]
Did anyone mention rev-matching on upshifts?

 

Ahh, I understand the confusion! I was referring to the original poster's question of downshifting from 6th to 4th in order to accelerate faster. You aren't going to be cornering on the limit in that situation, so a sloppy shift isn't going to cause a spin.

Double-clutching on upshifts is unnecessary in every vehicle because the transmission will slow down on it's own given enough time, and usually it slows down quicker than the engine does.

 

[QUOTE=captain_pants,Dec 2 2007, 06:20 PM] Heck, some street Subarus run dog-boxes with no syncros!

 

Double clutching is a shifting technique used on large or semi trucks or cars from the 30's or earlier with transmissions that don't have synchros. Race cars with dog boxes don't have syncros either but they don't drive in traffic either and therefore they are shifted without the clutch at all (also possible and commonly done in trucks but they have a lot more gears, haul loads in traffic and up hills so it's not always possible).

Double clutching serves absolutely no useful purpose on a transmission with synchros unless you're practicing for your truck driver's license or have a chimp and want to pretend to be BJ and the Bear.

 

While decelerating? Which successful autocrossers let the rear tires speed up the engine instead of matching revs before letting out the clutch?

 

what was that stupid line from the fast and furuious... vin Diesel...

you were granny shifting when you shoudl be double clutching.....

or something stupid like that... F&F FTW!!!!!

 

i disagree.

If you are in 6th gear, and want to downshift to 3rd gear to overtake someone on the highway, i always double clutch to get the right RPM! I was always under the impression that the synchros were not designed to take that big of change in RPM's. They were designed to take the difference between 1st to 2nd, or 3rd to 4th, not a 6th to 2nd, or a 2nd to 6th. When i double clutch correctly, the gear slides in perfectly, there is no thump or force i have to overcome to get it into gear. There is also no lunge when you let out the clutch, which makes it much smoother! At least in my opinion, i will continue to double clutch when i need to downshift multiple gears, as in my situation, it seems to have less stress on the syncros and is alot smoother!

 

what you describe sounds like rev matching, not double clutching.......

We all rev match with no clunking into gears or whatever you described..... it is way too time consuming to try to double clutch and actually would probably make it easier to mis a gear if you were trying to go from 6th to 3rd.....

 

1) Let go of the accelerator
2) Press the clutch pedal
3) Move the shifter to neutral
4) Let go of the clutch pedal
5) Press on the accelerator quickly until the RPMs hit a number I expect 4th gear to be in
6) Let go of the accelerator
7) Press the clutch pedal
8) Shift to 4th
9) Let go of the clutch pedal while pressing on the accelerator

This is what i thought double clutching was... if its rev-matching, then i just had the name confused!
This is what i do everytime im looking to downshift more than one gear. I can now do that very quickly with my 9lb flywheel.

 

That is double clutching & rev matching at the same time

Rev matching - 5) Press on the accelerator quickly until the RPMs hit a number I expect 4th gear to be in

.... but like everyone stated there is no reason to do the double clutching part...

i cannot imagine how much slower lap times would be when you are doing your double clutching....an extra 1/2 second per braking corner?

good luck either way.....