Hey i was just reading around and was wondering what everyones opinion on double clutching and rev matching. I heard that rev matching is faster (which it is) while it achieves the same purpose as double clutching but does not help the sychros as much as double clutching does. Which one does everyone prefer? The slower way (but more helpful for your sychros) or the faster way.

sorry if this is in the wrong forum

 

In my RX-7 I rev-match and rarely double-clutch. I double-clutch when the car is cold and not up to temps yet. Gears feel a bit notchy until it's warmed up a bit. After that I don't see the benefit in it as my shift feels exactly the same, just takes a longer.

 

double clutch?

 

I rev match every downshift all the time.

 

I had another question as well....to rev match...i heard u rev it up approx 1k rpm-2k rpm above ur current rpms to get a good smooth downshift. Is this always the case?

 

You need to rev up to, or past, the rpm that you will be at in the next lower gear.

 

rev it to where you think the engine is at.. you'll get good at it and should know in all gears without even thinking about it.
but really, just blip the gas, it should get it to around where you need it.

also, does double clutching even exist as a practical way to shift if your not driving a 1940's dump truck? or is it just because they said so in the fast and the furious..

 

Could someone kindly explain double clutching? I've heard this term scattered for years, but there seems to be a big mystery around it.

My understanding is that you start a shift and when the lever is in neutral you release the clutch, put it back in and then finish the shift. But then if you don't prod the throttle the revs by this time will be down at idle and the shock of engaging the clutch again would stress the driveline more than if you just shifted in a regular fashion wouldn't it?

 

so...without knowing the exact rpms i will be at...would it be correct to say approximatly 1500ks above ur current rpms would be sufficent enough for a nice smooth downshift?

 

Double Clutching is:
1) clutch in
2) go into neutral
3) clutch out
4) blip rpms
5) clutch in
6) shift down
7) clutch out

i think this is correct. Difference between double clutching and rev matching is u dont do step 3 and 5...u just blip rpms with the clutch in then shift down then clutch out

if im wrong plz correct me.

 

You guys more or less have it.

the theory in double clutching is that the extra step will spin the countershaft nearer to the revs it needs to be at for smooth engagement of the dog teeth. Basically double clutching does the job of the synchros.

 

I used to double clutch and rev match, but then I heard it's bad for the manifold...

 

minus 1 & R , you have synchros, unless your trying to flat shift ( full throttle loading) you don't need to do anything like double clutching or rev matching.. on down shifting it's up to you , use the gas and brake to keep spool up or let if drop off totally with torque braking.

Too much F&F, only boxes without synchros really need to be concerned about this..

 

Ahhhh, no thanks. I think I will continue doing rev-match downshifts when approaching corners, lights or just plain need a lower gear. Not to keen on using my spinning clutch friction disk on the slower rotating flywheel to bring my revs ups, I rather just blip the throttle and save my clutch from some wear.

 

ah quit being so dainty... Just kick and shift.....better yet dont even kick, just shift..

 

I've burped the throttle over using the clutch forever, and have never had a tranny/clutch go out of commission as a result.

One thing to the question poster that I didn't notice anybody mention....

Don't put much preasure on your stick.... iow don't try to force it in. You'll feel it just click in when the rpms are right. (up or down)

Screw your tach, use your ear instead as it knows best.

Make sure when you upshift you rev higher than what rpm you'll be shifting into then let that gear shift "fall" into place. Never try entering a downshift on the up revs..... never r5ev up just "to" the proper rpm either.... it will go in easily, but can have a real nasty gear engagement.

At least that's the way my corolla gts and celica gts were.

 

I used my ear to synch the carbs on my VW.

There is also the chassis dynamics argument that a match-rev downshift will upset the chassis less, alowing you to grab a gear after turn in (not that you would ever do such a thing)

 

When driving my RX-7 in 'Race' conditions:

I just hammer it into gear from 1st to 2nd WOT, no clutch. 2nd to 3rd I gently tap the clutch to 'break the tourque' and ease it out of gear and into gear, really fast. Same follows for all upper gears. On hard downshift I pedal to metal using clutch as you normally would only by the time Im in the next lower gear and the clutch is engaged, the RPMs are matched so I never miss.

I havent tried any of that in my 2nd Gen so I dont know how well it works there. But on my 1st Gen, thats how I did it. Pretty wild, but then again Im a beast behind the wheel.

 

I would have never believed this until I got an actual demostration from you about the "kick and shift" method. Don't think I have the guts to try that. WAY too hardcore for me....at least for now.

 

what do u mean it should just fall into place? So u should feel minimal resistance when shifting down? For example you should feel the same resistance as u would shifting up 1st to 2nd and etc? Don't really understand what u mean by force it in and u'll feel it just click in, but id like to understand what you mean.

 

Between 1st and 2nd you DO have to at least let off the throttle for a split second though right? just so that the shifter isn't torqued

 

You strictly do it by feel. You can break out the calculator and calculator the RPMS and tranny speeds since the gear ratios and final drive ratios are in teh FSM.

Just drive the car and you will get a feel for it. The pedal setup is already very nice from teh factory. Nicer than any other car i've driven except teh miata. It's practice makes perfect.

Once you get a feel for the car you don't even need to look at the revs or anything. You can't look at the revs anyways when you are full throttle in 4th gear and trying to make a hairpin turn at the end of the straight trying to grab second for exit.

You rev match on the downshift only and I repeat ONLY when braking in a straight line in prep for using the gear to balance the car through the apex with your gas pedal.

 

when driving "normally" on the streets I rev match almost every downshift.

I'll double clutch... sometimes. Usually into 2nd from high RPM, just because my 2nd gear syncro is a little iffy, but usually just match revs and go.

it makes it MUCH smoother and is MUCH nicer than that looooooonnnngggg clutch drag some people seem to think is cool when downshifting.

 

Guys rev matching and double clutching are the same exact thing. Just so happens that rev matching refers to double clutching when down shifting because of the necessity to blip the throttle before re-engaging the clutch. On up shifting, there's no need for this because the input and output shafts of the tranny will automatically match speeds.

Since my second gear sychro is totally messed up i double clutch on a daily basis. Here's a good guide that I read through:
http://www.waycoolinc.com/z3/essenti...e/shifting.htm

 

..and how is that expensive dogmission of yours doing....

BTW This thread should not be considered dainty until ShaunO posts... hehe (J/K!)