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      02-07-2008, 02:52 PM   #12
jdink's Avatar

Drives: '08 E90 335i 6MT
Join Date: Jan 2008
Location: Portland, OR

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Originally Posted by mantis View Post
Rev-Matching technique: Double Clutching

Correct me if I'm wrong, which probably am.

When you downshift to gain more power your engine will be spinning at a higher speed (higher RPM). Synchronizers will be spinning harder to to synch the speeds. It is a good practice rev-match.

Rev-matching is manually bringing up the RPM before engaging the lower gear you are shifting into. So when you ditch your clutch, your synchros will not have much to do, and they wont wear out.

This is how it is executed: (let's say you are going on 5th gear cruising at 50 mph, and you want to pass someone, so you want to go to 3rd gear)
1. Depress clutch
2. put gear in neutral
3. Undepress the clutch
4. blip your gas to bump it up 1500-2500 RPM's more (Do not take the #'s literally here, i dont know im just guessing, but you'll get that down by practice/experience)
5. Depress clutch again
6. put shifter in 3rd gear
7. Undepress the clutch

The beauty of this technique is it has to be done in less than 1 second (sure with experience and practice)

This is an exercise to get your foot used to the concept if you have never done it. This is basically a short version of it for practice, to get you to the real double-clutching

1. Depress clutch
2. put gear in neutral
3. blip gas
4. engage 3rd gear
5. undepress the clutch

(note: the 5 steps i just listed are not enough, they do not synchronize tranny's internal parts spinning speed - you need to blip gas while clutch is undepressed to synch the speed of flywheel *i think*)

practice that ^^ a few times when in open road, and when safe. Then double clutching will be real easy.

+1 Exactly how my friend explained it last night he was testing out my 335 (I wanted his opinion on the CDV)