Single Clutch Movement Rev Match

[Rekin]

Hey,

When downshifting the most correct term expressed by everyone is to;

clutch in - shift neutral - let go of clutch - rev match - clutch in - change to lower gear

Although playing around whilst driving doing the following step seems to work also;

clutch in - neutral - rev match - change gears

Why do people always mention to let go, rev, clutch in when the single clutch method seems to work exactly the same?

Thanks

Patrick

[lingeringsoul]

Because there's way too many idiots watching FNF.

I've only ever seen double clutching done in a V8 race car. Never in any videos and real life have I seen it being used anywhere else.

[djr81]

You only ever really needed to double de clutch when your gearbox had no synchros (or the dog clutches were marginal & needed looking after). All it does is get the gearbox shafts up to speed thereby removing the load on the synchros (or grinding the gears).

No one since 1950 something needed to do it.

[Merli]

Yeah, it's from old gearboxes that don't have synchros...

The process was:

Clutch in - Move to neutral - Clutch out - Clutch in - Move to next gear - Rev Match - Clutch out

[r33cruiser]

double clutching is an art. bloody hard when u start. make sure u practice in sparce traffic too.

it is primarily used to keep the revs up=faster e.t.

but its mainly just a show off thing on the street for the honda's and holdens to show off their loud exhausts :thumbdown:

Edited February 1, 2008 by r33cruiser

[grigor]

Yeah, it's from old gearboxes that don't have synchros...

The process was:

Clutch in - Move to neutral - Clutch out - Clutch in - Move to next gear - Rev Match - Clutch out

No that won't work.Try:

clutch in, shift to neutral, clutch out, rev match, clutch in, select gear, clutch out.

With a heavy killer clutch pedal,

clutch in, shift to neutral, clutch out, rev match, select gear.

If you're doing thousands of gear changes, dropping just a few clutch/de-clutches is heaven.

[VB-]

Yeah, it's from old gearboxes that don't have synchros...

The process was:

Clutch in - Move to neutral - Clutch out - Clutch in - Move to next gear - Rev Match - Clutch out

that wont work, you need to rev match in dog boxes to ENGAGE the gear.

Rekin, from what i got, you were asking why people let the clutch out as opposed to the way your doing it, everyone else is telling you why people double clutch, not why they do it that way, so:

you let the clutch out while its in neutral, and give it a rev to match the speed of the clutch with that of the output shaft on the box, allowing for the raio of the gear your trying to grab. a practical example,

say you've only got two gears, 1st and second, the ratios are 1:1 (2nd gear) and 2:1 (1st gear)

your doing 20km/h in second at 1000rpm, you double clutch, bring the revs up to 2000rpm, so your clutch is spinning at 2000rpm, your output shaft will already be spinning at 2000rpm, and so will first gear, everything is the same speed, gear will slot straight in.

if i f*cked any of that up please correct me so i dont confuse rekin

PS - thats how u shift without the clutch also, pull it out of gear, rev match, and because everything is pinning at the same speed, gear with slot straight in, but its hard to do, i still crunch occasionally when i do it, and i practiced it a fair bit. man i do some terrible things to my gearbox.....

PPS R33cruiser, none of what you said makes sense, its got nothing to do with running at the strip (you said e.t. and im guessin your not talking bout the litte green dude on a bike lol)

Edited February 1, 2008 by VB-

[Duncan]

lol yeah I abuse the gearboxes every now and then practicing changing without the clutch too, and I only get it right 9 times out of 10....the other time leads to that nasty griding gear noise.

much easier to get right on the track where you get to practice the same gear/revs over and over again. And the higher the difference in revs the easier it is to slot in for some reason.

[GTR-32U]

Honestly it all sounds like a hollywood wankfest to me.This technique is what I use when I drive a non synchro heavy vehicle ( Crash box )...But as even most late model trucks are going Synchro also its not something I have done in a long time..As for a performance application I fail to see any merit in it ( unless you like to wear out transmissions from the grinds )...Pressing the clutch pedal is the slowest part of a typical gearshift...So why do it twice ? I would be up the road chirping 2nd while your still stuffing around pressing the clutch ....waste of time...Synchros are there for a reason

[VB-]

dunno about you, but we're all talking about downshifting. so do you snap second and start skating when approaching a red light or something? only jk mate

it has no 'performance' benefit, but in my case, its smoother if i want to shift down to overtake, but the main thing, is with all the abuse i give my box from shifting without the clutch, syncros are kinda feelin it now, so i do it to reduce the load on them, as to preserve the remaining life in the box.

think of it this way, i never used the clutch, now im using it twice as much to make up for it hahaha

[GTR-32U]

I understand your point about the smoothness part of it all.However the term seems to be only used in a race scenario when upshifting fast is required...The only technique which I have used effectively ( And has a very,very small Gain ) is when upshifting fast pull out of gear without pressing the clutch and just a quick stab on the clutch while shifting up ( tearing gearstick outta the box style )...As for Downshifting for overtaking etc...Whilst foot flat on the accelerator press clutch and downshift without taking foot off the accelerator at all...If its done fast ( must be done fast ) it helps..specially in a laggy turbo car ( RB20 )

[joeyjoejoejuniorshabadoo]

for overtaking etc...Whilst foot flat on the accelerator press clutch and downshift without taking foot off the accelerator at all...

you find you need to flat shift in traffic?

i used to go clutchless style in my old cars... but after the wad i've spent on the skyline i'm SOO not game to even try

[Rekin]

i stumbled across this website;

http://forums.nasioc.com/forums/showthread.php?t=804223

Basic driveline stuff: for this discussion we can break the drivetrain into 3 groups, 1) engine/flywheel/clutch pressure plate, 2) clutch disk (just "clutch" in the discussion below)/transmission input shaft (which the clutch disk is attached to)/any gears splined to the input shaft, and 3) transmission output shaft/any gears splined to it/diffs, driveshafts, wheels. (Note: yes, reverse gear requires another shaft and idler gear, there is a (or >1) layshaft involved, but all that's immaterial to this discussion.)

Driving: all 3 groups are tied together, the first 2 by the flywheel/clutch/pressure plate sandwich, that latter 2 by the single set of gears linked together for the "gear" you're driving in, one on the input shaft, one on the output shaft.

Clutch disengaged: (clutch pedal pushed down) first group is disconnected from 2nd and 3rd groups, which are still connected.

Neutral: 2nd group is disconnected from 3rd group; 1st and 2nd groups connected. If the clutch is also disengaged then all 3 groups are disconnected from each other.

[Haysey]

ive seen my old mechanic sucessfully double clutch on upshifts and downshifts on my old 32, he was doing it so fast i was having trouble working out what was happening, the car was staying on boost longer and definately holding more boost... amazing when its done properly!

i had to learn proper rev matching when i got my HC licence as i did it in a crash gearbox that has no synchros at all... so if you dont get it right in a 35tonne truck then you aint moving away from those lights anytime soon!

[Merli]

you let the clutch out while its in neutral, and give it a rev to match the speed of the clutch with that of the output shaft on the box, allowing for the raio of the gear your trying to grab. a practical example

Yeah, that's it