What exactly is it...When is it needed...& how do you do it??

 

Rev-matching is the process of changing the rpms of the engine to the speed required for gear you are shifting into. This way when you let out the clutch it does not disrupt the balance of the car.

When you upshift and pause for a split second to allow the rpms to drop to match the next gear this is a form of rev-matching. when you get it right you can let out the clutch as fast as you want without upsetting the car.

On downshifting it is a little trickier. What you do is blip the throttle to raise the rpms while the clutch is pressed in to raise engine rpms to that of the next lower gear. Done right you can let out the clutch as fast as you want without upsetting the car.

This revmatching is 1/2 of the heel to maneuver. Once you have the rev-matching down the next step is to combine with braking.

When to use: I use it all of the time on the street to provide a smoother drive and put less stress on the drivetrain. Plus it is like training for the track where I heel-toe. Some claim to heel to on the street but I find it hard to do if I am not braking hard.

If you want to try: start by driving down a high way in 6th gear try going from 6th to 5th as smooth as possible. A blindfolded passenger should not know you shifted. Once you get this down try to go from 5th to 4th 4th to 3rd at different speeds at different rpms. It takes a while but is quite rewarding when done right.

 

If you want to extend the life of your clutch, you need to do it all the time. With the torque of the LS1/LS6, rev matching really isn't required to shift smoothly. If you really want to learn, get a super light car with a weak powerplant and a race clutch. My learner car is a CRX Si with a six-puck race clutch. The clutch is basically an on-off switch, so if I don't want to buck the car when I shift, I have to match revs perfectly. Before I blew the head gasket, I was getting good enough that I could occasionally shift perfectly without the clutch...but sometimes my shifts would get f'd up too...

 

I actually double clutch, and blip the throttle with the clutch out but with the transmission in neutral, then clutch again and make the downshift. That way you not only match engine speed with wheel speed but bring the front end of the transmission up to speed also.
If you blip the throttle with the clutch in, you are still relying on the synchronizers to match the input gear speed to the output gear speed. With the clutch engaged, you also do the work for the synchros.

 

Actually if you do it right you don't need the clutch. But I would not recommend it long-term.

 

Double clutching is the way to go if you want to be smooth and easy on the equipment.

Throttle "blipping" is just for drivers who should be using an automatic. Sad, but true!

 

Thanks 4 the info guys! Very informative. I actually tried it today...got it right 4 outta 5 times. Shifts a lot smoother when done properly.
So the best way to down-shift is clutch in...shift to neutral...clutch out...blip gas pedal to match revs...clutch in again...shift to lower gear..right??
One more question...by "matching revs" does that mean try to blip it so tach is at the same rev it was at before making the shift??

 

You're matching the engine RPM to what it would be if it were in gear for that speed. For instance, assume at 80mph in 6th gear you do 2,000rpm. When you go from 5th gear (say it's at 2,700rpm) at 80mph to 6th, you put the clutch in and set the engine at 2,000rpm and then do the shift. This way the RPM is at where it would be when in gear.

 

Same thing for the downshift...if you're in 6th at 80mph and your RPMs at are 2,000 and you want to go to 5th, you match for what the engine RPM would be in 5th before letting the clutch back out. Clutch in, put into 5th, rev to 2,700, clutch out. And when I say rev, I mean just a blip of the throttle.

Hope that helps

 

With modern trasmissions that have syncros double clutching is unnecessary. It is ok to do on the street, but on a track (road course not 1/4 mi.) it slows your shifts and draws your concentration away from line. I have been a passenger with many instructers at speed on the track and never seen one double clutching.

As far as your second comment. I really see no need or use of adding insults to this. This should be an informative thread please do not ruin it.

 

Whats the difference between pushing in clutch... blipping throttle....shift to lower gear & pushing in clutch...shift to neutral...blip throttle..push in clutch again..shift to lower gear??

 

Ok...lets call the first rev-matching, and the second double-clutching. The theory behind double-clutching is to get the internal transmission components (the syncros) to be up to speed. A simple throttle blip in neutral will get them spinning faster, thus make them work less when the next gear is selected. As pointed out above, it's pretty pointless these days, but to each their own.

With rev-matching, you assume that the syncros will do their job without any help from you by jumping them up in speed. Rev-matching is mostly to do with the engine RPM, and not putting concern on the syncros.

 

"Blipping" the thottle only matches the engine to the drive line speed.

Double clutching matches the engine, drive line AND transmission speeds.

DC is easier on the transmission and is much smoother as well. There is nothing "Modern" about the synchros in our transmissions. Cadillac had synchros in 1928. Once you start DC'ing the process goes very fast and becomes second nature.

I don't care what race car drivers do. Our Z06's are not race cars and 99% of them never see the track.

 

Where'd this comment come from, and what do you mean by it?? My car goes to a few autocrosses a year and definitely sees some hard driving, and when I'm diving into a corner, I don't waste my time double clutching...instead I worry about keeping the car balanced and not f'ing up.

 

I think you would be surprised at how many Z06s make it up to the track. I have never gone to an event where there was not a significant number of people driving Z06s. And many would argue that our cars are really street legal race cars. To each their own. Just understand that there are people out there that use their car differently then you do and we will all be happy.

 

Good link a description of what to do Heel/Toe

 

I would bet a months pay that more than 1% of Z06s make it to auto-x and/or tracks!!!
Double clutching is not needed at the track, just heel&toe, and the synchros we have today with friction material and our trannys using AT fluid are a little different than the ones used in the '20s.