Originally posted by Tiger740:
What exactly is rev match/double clutch?
I know that rev matching is a way of double clutching, but how do you exactly match the rev?
Thank you.
Rev matching is not a way to double clutch, though as part of double clutching you will typically rev match.
People can go on for days about the nuances of all this, but in short...
Rev matching means while you have the transmission between gears during a shift, you use the throttle to match the RPM of the engine to the RPM it will be when you put it into whichever gear you are getting ready to shift into. This is typically done by "blipping" the throttle. See "heel and toe" below.
Double clutching (aka double declutching) is, in my opinion, not really needed in a modern car with a syncrhonized tranny, but you can still do it and some will argue it offers benefits on the race track because it matches shaft speeds, etc. in addition to engine speed. If you ever drive some commercial vehicles, a really old car or truck, or a vehicle with a blown synchro, it can be a very handy skill to know. Basically you:
1) Get off the throttle and disengage the clutch (pedal down).
2) Shift the transmission to neutral
3) Engage the clutch (pedal up).
4) Blip the throttle to match shaft speed to speed of new gear. (see heel and toe below)
5) Disengage clutch (pedal down)
6) Shift from neutral into desired gear
7) Engage clutch (pedal up) and apply throttle as needed
1 - 3 can be done quickly or slowly
4 - 6 must be done quickly
If 7 is done quickly, the engine will be 'rev-matched' to the rest of the drivetrain
Heel & Toe is the somewhat mislabeled technique whereby you use your right foot to both brake and blip the throttle at the same time. I say it is somewhat mislabeled because most people in most modern cars use the side of their foot more than the actual heel to blip the throttle, but do whatever works best for you. To heel and toe, you put the forward part of your foot securely on the right side of the brake and press the brake to slow the car. While doing that, you roll your foot to the right to blip the throttle. The exact position of your feet during all this depends on the car and pedal placement, the size of your feet/shoes, and your driving position. This is how you can double clutch and rev match when it counts most - under braking as you go into a turn.
This all takes practice. I suggest starting with heel-toe rev matching, then work up to double clutching.