Well guys, don't know what to make of this, but check your facts before you tell someone they are confused!! Double clutching is exactly as I defined, per "Bob Bondurant's Book on High Performance Driving", basically to the word. The neutral gate must be used and the clutch must be engaged to make it double clutching. "Rev matching", is there such a term? no. I think we would be refering to heal/toe? There is a difference, check a professional source, perhaps a book or driving manual, if you cannot take my word for it for some reason or another, Soy

 

Actually dc'ing doesn't get the driveshaft spinning, it get's the transmission input shaft and disc spinning up to the speed of the engine, the driveshaft speed is always in direct relation to the rear wheel speed. Nontheless, props to Soyinside for the most informative post on all these subjects. I new nothing about heel- toe, till now

 

holy crap

i think we are all sleepy need some good sleep

 

soyinside is exactly right about double-clutching and simple rev matching. if you push in the clutch, then rev match, then downshift to a lower gear this is simple rev matching. in double clutching, heres how it goes. push in the clutch, go to neutral, release clutch, rev to proper RPM(this engages the disc and the input shaft of the tranny to bring these components up to speed also, not just the engine alone) this is not possible with simple rev-matching!!! thats the defference. right, soyinside? you tell em. take notes, wickerbill.

 

OK, I skipped your elaborate post about double clutching because it was too long and I already know what it is. I went back and read that post and it was mostly right, but the part on how double clutching helps increase your turning traction isn't completely true. Since I have been told in this thread that I don't know what I'm talking about, I guess I'll have to prove that I do.

Double clutching does not "get the driveshaft turning" as you say in one of your posts. It speeds up the input shaft of the transmission to get it turning to the speed it would be turning at that given speed in the lower gear you are getting ready to downshift into. Our transmission has synchros that will do this same thing without double clutching. If you push the clutch in, rev the engine to match the RPM's to the gear you are shifting to, shift into gear and let the clutch out, you will get the same result only much quicker. I have driven the S2000 at the track and hard around town and have yet to find a single reason to double clutch. Rev matching (yes, this is a proper term) works just fine on this wonderful transmission we have. The result you mentioned in your post above, would also be possible with rev matching.

I have had cars in the past where the synchros didn't work too well and double clutching really helped in the downshifting. Keep in mind the racing books, at least the ones I have, are referring to driving real race cars. Real race cars don't always have synchros in them to allow you to just do simple rev matching downshifting. In these cars it is required to double clutch. Our cars aren't like this and where you talk about maximizing turning traction, we could just do simple rev matching and get the same results and it would be much easier and quicker for the driver.

Rev matching is the proper term for what I described, not heel and toe. Heel and toe is when you are braking and need to downshift. You use your right foot to both brake and rev the throttle to match the revs needed when downshifting. Being smooth is the key to not upset the balance of the car. You can rev match downshift without heel and toe if you are not braking. An example would be if you're downshifting to pass someone on the highway, there would be no reason to heel and toe since you aren't braking. Just push the clutch in, match revs, downshift, and then engage the clutch.

I think overall this thread is good because people are learning a great technique to extract the maximum performance from their cars. I just don't feel like we need to double clutch and many other threads on this board have agreed with me. I used to really believe in double clutching with some of my older cars where it helped and didn't believe that the S2000 didn't need it until I got mine. Now after having it for a while and driving it on the track, I've come to agree that it's not necessary. Simple rev matching is all that's necessary.

Mark

 

Funny how this topic pops up on a regular basis. All this talk of DC'ing, heal/toe, rev matching, quotes from the "Bondurant" racing school text book, etc. What you would be taught and what you would do IN the driving school is not necessarily what shows up in the printed book. Things such as typos and printing errors can result in a slightly different skew on things. And that whole bit about spinning up the drive shaft ............. WOW! Thank God someone caught that.
Another board member PM'ed me not long ago with this question. Here is a "copy/paste" of my response back to him (I'll put it here so you guys can pick it apart):

(The question was: What is double clutching - when and what to use it for?)
Double clutching (DC) is really not necessary in today's modern trannies with synchronizers. Before synchros, DC was used to match gear speeds so they would mesh efficiently without grinding. This was used more for downshifting and occasionally used for upshifting. In our car, you will have probably noticed that when slowing down, it is sometimes difficult to engage 1st gear if your car's road speed is too high. A thing called a "blocker ring" in the tranny makes this difficult on purpose so you don't grind up your 1st gear. There are blocker rings in other gears, too, but they do not intervene nearly so aggressively. With DC, you can sort of defeat that blocker ring and this makes it possible to downshift into 1st gear at a relatively high rpm and high road speed. Of course, if you do this, make sure that after the downshift, your rpm is not at or over redline so don't downshift to soon.
Here's how you would do it. Keep in mind this is done very fast.
Suppose you are slowing down and you are now in 2nd gear. Your rpm is still a bit high but you want to downshift anyway and you know that after the downshift, your rpm will still be below redline.
1. Push clutch in, move shifter into neutral, let clutch out.
2. Blip throttle aggressively.
3. While the revs are still high, quickly push clutch in, shove shifter into 1st, release clutch. You have now double clutched into 1st. You can also do this downshifting into any lower gear but with our synchros, only the 2-1 shift makes it required.
NOW, if you are too slow in step (3), you can do the following instead:
3a. push clutch in, shove into 1st gear, blip throttle again just before releasing the clutch.
ONE MORE THING:
If you now wish to maintain braking into a corner while downshifting, you can operate the brake AND the throttle (for blipping) at the same time. You use your right toe for one of the pedals and your right heel for the other pedal and VOILA! You've just HEAL/TOE, double clutch, downshifted. If you don't do the DC, then you've just heal/toe downshifted. You wouldn't use this in street racing unless you are racing someone around corners and curves. You would not use DC in a drag race.

ps. You can rev match WITHOUT double clutching with exception to the above example. ie. high speed downshift into 1st.

 

Well said xviper.

I'd just like to add that getting the DC perfect consistently is nigh on impossible. Matching revs when clutching out is easier because you can still modulate the clutch engagement.

To know wether you have DC'ed properly you can actually skip 'clutch in' during step 3 and the shifter will slip nicely into the desired gear easily.

This is also called clutchless shifts and is regular done by racers with straight cut gear boxes for left foot braking. Keep it up with your stock box and you'll grind out your syncros in no time.

Heel and toe is crucial in attaining maximum grip during braking and corner entry. It will avoid wheel lock ups, which happens when you clutch out quickly while the engine revs are still low relative to the in gear revs.

Try this for a clearer picture.

Accelerate up in 2nd up to 7500 rpm. Maintaining speed, clutch in momentarily and let the revs drop to idle. Then clutch out quickly and you'll be faced with sudden engine braking and possible lock up of the rear drive wheels.

Imagine this happening when you're on the limit turning into a corner. You could easily spin out.

Try it again but blip the throttle to the same revs again (rev-matching). You can then clutch out as fast as possible without the earlier drama.

Hope this helps.........sorry to appear like I'm spelling out the obvious but I've met plenty of folks who still don't grip this essential driving concept.

 

DC = reduced wear on tranny synchros when downshifting.

Rev Match = reduction of annoying decelleration jerk when letting the clutch out after down-shift, reducing clutch wear.

?

 

More importantly it allows downshifting without disturbing the balance of the car at the limit. If you downshift without rev matching at the track while braking hard into a corner, it's very likely you'll spin out.

 

heal = what you do when you're wounded
heel = the round part at the back of your foot