stickben

I saw the movie "The fast and the furious" :rolleyes: :rolleyes: today and they said something about "double clutching" what is that? Is that just a ricer thing?

Stingy74

Isn't that where you blip the throttle to mach revs with the transmisson while the clutch is pressed in? I think it's a trucker thing...

ddn

Double clutching is a technique used when racing to match the layshaft speed to the engine speed. It is used only when downshifting. It is also intended to be used on transmissions without synchromesh, but can be used on a transmission with syncrhos to make them work less.

Basically it goes like this:

1) Blasting along in 3rd approaching a 2nd gear corner
2) Push in clutch
3) Select neutral
4) Let out clutch
5) Blip throttle to match revs of engine and layshaft
6) Push in clutch
7) Selected 2nd
8) Let out clutch and mash throttle

As far as the Fast and the Furious, I know exactly what you're talking about where he says "Granny shifting, not double clutching like you're supposed to". It is beyond me why anyone would double clutch when upshifting, especially in a drag race. I've never heard of it, maybe I'm wrong.

I have to double clutch the 1970 Fiat 500 my dad has in Italy :) No syncrhos

bence13_33

stickben:
Stingy is right, you bleep the trottle a little bit in between your shifts to keep your RPMs up. I really can't see why you'd use double clutching while racing down the 1/4 mile? Here are some other shifting terms

"Powershifting" - Keep your foot to the floor, jam in the clutch and shift gears and let the clutch out as quickly as possible (while keeping your foot to the floor). This needs to be done quickly so as to not over-rev the engine.

"Straight sticking" - No clutch is used, whenever you desire to shift gears you rip it to the desired gear.

Both are very hard on the transmission and require some practice.


[Modified by bence13_33, 6:27 PM 1/5/2002]

jbroughton

Yeah, basically it's just what it sounds like - you're pushing the clutch in twice at each gear change...as David says, used mostly for trannies with no synchronizers (or in my case, bad synchronizers). I have to do that for the 2-3 shift and 3-4 shift to keep the gears from grinding as I shift. A royal pain in the ***, and I don't know how it would benefit anybody for drag racing, since it slows the shifting process considerably.

Jeff

ddn

Stingy: Actually, I should have mentioned this. Blipping the throttle when the clutch is pressed in serves no purpose at all as the layshaft is then not connected to the engine. That's why you have to let it out, blip, press it in..it's much slower, and as far as I'm concerned no one would EVER do it drag racing.

Stingy74

Yeah, i'd have to agree. There's no reason to double clutch in a drag race. I don't think it could be done fast enough. Just some unresearched fancy words they gave to the actors to make it sound as if they new what they were talking about.

Chuck Harmon

Double clutching while upshifting through forward gears is nothing less than ridiculous! If you are at 6000 rpm in 1st gear and shift to 2nd, the rpm should drop to ~4500rpm. To shift smoothly, the engine needs to slow to 4500 before releasing the clutch. If you develop a sensitive feel through the shift lever you can actually feel the gears mesh. The syncros wouldn't have to have worked at all in this example. If you shift so quickly that the engine is still near 6000 rpm, the syncros have to work hard to enable the gear change without grinding.

A light flywheel allows the engine to drop revs more quickly allowing faster shifting without working the synchros. They also rev faster once in gear!

Double clutching is a wonderful skill to develop. Being able to shift with absolute smoothness down through the gears with no tendency of going through the windshield on down shifts is a true point of pride to a sports car driver! ddn did a great job of explaining the technique.

Chuck



[Modified by Chuck Harmon, 5:05 PM 1/5/2002]

stickben

ya, that wouldnt make any sense if you double clutch while drag racing. I guess it would save you some time by keeping the rpms up while shifting. Heh i might have to try it in my toyota. :smash:

Paul 75 L82

Guys, ain't it great to have a corvette C3. Had a few good drives today. I just love my Hurst.

BAD-L88

I was going to ask about this but you are addessing it here.

I always try to match up the revs (blip the throttle )but instead of pumping the clutch twice I just hold it down. I have always thought it made downshifts smoother and less jumpy. Are you telling me it has been in my head and I have been wasting my time? Can't be, when I do nothing in any of my rides I get a hard jerk. :eek:

Please explain more. :seeya

96z71

Please forgive me for my stupidity, but what is a Layshaft>?

-Jake :hat

68shark

I'm with BADL88 on this one. Matching rev's is one of the skills that sets apart very good "stickshift" drivers from ordinary ones. Nice to smoothly go from 4th to 3rd to 2nd using the engine to slow the car, jump on the brakes, accelerate through the turn, then go back up through the gears. Double clutching is not necessary to accomplish this.

Double clutching though is recommended in my '68 Owners Manual but I believe it is totally unnecessary in a full synchro transmission. I did own a '39 Plymouth Coupe about 20 years back (stock) that had a non synchro transmission. Even with this, with practice, taking your time, I learned to downshift smoothly without double clutching. I double clutched for awhile until I figured out that if you take your time and match rev's you don't need to bother with this.

My .02.....

vert2go89

Double clutching was basically used when driving old trucks since they didnt have synchronizers and you had to get the gears turning same speeds to match for a shift.No it is not a racing thing as your shift would be to slow.

paso

Well on behalf of the older generation Almost all standard transmission before 1953 that did not have full synchronmesh transmissions you almost "always" double clutched between 1 st and 2nd and 2nd and third. I learned to drive that way. If you didn't double clutch on the way up you always got a little "grind" as you entered each new gear. You also double clutched going from third back to second. You "NEVER" I Mean Never went from second to "first" or your tranny was all over the road, if you did while you were still moving. When all the "old Guys" get up in the morning and read some the above post's Or when they stop laughing They will post some of their early drivers:) When the 55 Chevy came out it had a fully synco tranny for every model. Not sure what the 53 Vette had but I had a 53 Chev and I had to double clutch. they also had Very weak tranny's went thru probably 5 In my early teens. Not sure if it was weak tranny's or early teens that wrecked them.:) :lol:


[Modified by paso, 10:15 PM 1/5/2002]

Chuck Harmon

Quote:
________________________________________ ________________
No it is not a racing thing as your shift would be to slow.
________________________________________ ________________

For racing it's done, "heal toe"

Bad L88,
Single blipping makes the shift more comfortable and is easier on the clutch, double blips are easier on the synchros. I used to drive an old dump truck without synchros. And yes, I did double clutch down into 1st too. Smoothness is the key, very easy to twist the tranny in half. Transmissions are always weakest in first gear. It is the greatest torque multiplication within the case. Smoothness is also the key in winning races. Parts last much longer if you treat them well. Road courses need a smooth touch to get around the fastest and to stay going 'round the track.

Chuck

ddn

Right it's not a drag racing thing. Wrong, it's very much a road racing thing.

96z71: The layshaft is the shaft in the transmission that has the gears on it.

BAD-L88: It's partly in your head, and it's partly real. Matching the speed of the engine to the speed of the car will obviously make for a smoother shift, and you will do this with blipping the throttle. It however doesn't change how much the synchros have to work, because you're not changing the layshaft speed. Keep doing it! :)

BAD-L88

Thanks for clearing that up. So just matching the revs does make for smoother driving.

I have been trying AskJeeves.com lately and am finding it rather informative. Here is an article that covers transmissions, double clutching, synchros, and has some great diagrams.


Go to http://www.askjeeves.com and type in "how does a transmission work"


[Modified by BAD-L88, 11:57 PM 1/5/2002]

marky mark

I watched the DVD version of "Bullitt" the other night and Steve McQueen double clutches in all his upshifts during the chase scene. The other driver (the "Bad" guys in the Dodge Charger) does not. I don't know if it has any positive affect while upshifting though. Perhaps Mr. McQueen, an accomplished racer himself, did it to add to the excitement and sound of the chase scenes, which still are great 30+ years later. FYI.

Speaking of the "Fast & Furious", I had to laugh a bit when the Vin Diesel character speaks in awe of his deceased Dad's Charger and says he doesn't drive it because he's too scared of it. That was a bit rich coming from a guy who's driving 10 sec 1/4 mile ricers throughout the movie!:lol:

Regards, Mark :flag :chevy