Is there any benefit to double clutching?

"Nauraushaun" (nauraushaun12) 11/15/2016 at 20:53 • Filed to: MANUEL

0

46

At all?

AW11 for your time - goddam these things are quirky inside!

I know that we have synchronized transmissions these days, that double clutching used to be necessary but now is not. But I don’t know if it’s beneficial at all.

!!!error: Indecipherable SUB-paragraph formatting!!! used to crunch sometimes when moving to second and fifth. I started double clutching and it stopped happening, so to this day I double clutch on every shift. I guess that means the synchros were worn - which implies double clutching might prevent them from wearing. But perhaps depressing the clutch twice as often is causing more wear on the clutch to counter-act that - I don’t know.

There’s a lot of misinformation on these topics. A combination of older folks who had techniques like this beat into them but never understood why, and people who preach things because they sound right with no formal evidence whatsoever. Much like people who tell you to engine brake to avoid wearing the brakes which is laughable.

What say you Oppo?

My citroen won't start > Nauraushaun 11/15/2016 at 20:56

3

Just put it in D

HammerheadFistpunch > Nauraushaun 11/15/2016 at 20:57

6

CB > Nauraushaun 11/15/2016 at 20:58

4

Fun fact*: dual clutch transmissions were designed with a second clutch in order to successfully mimic the benefits of double clutching with an automated system.

* This is a lie.

AntiSpeed > Nauraushaun 11/15/2016 at 21:01

3

You don’t need to double-clutch on upshifts with any modern gearbox. Probably not on any gearbox made after World War 2.

On downshifts the main benefit is that it makes your car sound like a race car. You can make your decision on whether or not it is necessary based on that.

Much like people who tell you to engine brake to avoid wearing the brakes...

Next time someone says this, tell them it’s to avoid *overheating* the brakes, like if you’re coming up to a stoplight/sign at the bottom of a very steep hill, or if you’re coasting down a hill with a very heavy load or a trailer. It’s not long-term brake wear you’re concerned with, it’s acute overheating.

Flavien Vidal > Nauraushaun 11/15/2016 at 21:01

1

No it’s not anymore. Rev-matching on downshifts and heel and toes under braking are both better for your clutch though.

Engine braking is pretty much needed if you live in mountainous parts. Nothing more fun than having your brakes overheat like crazy while going down l’Alpes d’Huez lol. How much you “use your brakes” doesn’t really matter (though you can warp your discs fairly easily which is expensive), but being able to stop and slow down does.

nermal > Nauraushaun 11/15/2016 at 21:03

3

I find double clutching necessary on cold mornings in my truck. After it warms up, no benefit.

hike > AntiSpeed 11/15/2016 at 21:04

0

Also mention how much cheaper it is to replace brakes instead of the damage from unnecessary wear to drivetrain components.

Berang > Nauraushaun 11/15/2016 at 21:06

1

Double clutching on downshifts has some benefit in saving the syncros in the lower gears, but beyond that, you’re just putting more wear on the throwout bearing and wasting time by doing it on upshifts.

MonkeePuzzle > Nauraushaun 11/15/2016 at 21:12

0

well.... i think double clutching is often confused with rev matching

modern cars need neither. rev matching though can keep the car in the sweet spot in the power curve as you shift

Jarrett - [BRZ Boi] > nermal 11/15/2016 at 21:14

0

This. I HAVE to double clutch 1st to 2nd in my miata when it’s cold.

404 - User No Longer Available > AntiSpeed 11/15/2016 at 21:14

2

On downshifts the main benefit is that it makes your car sound like a race car. You can make your decision on whether or not it is necessary based on that.

I thought that was rev matching, not double clutching. Rev match is bliping the throttle for engine speed to match, double clutch is letting out the clutch in neutral and clutching back in so the driveshaft speed sync.

TheTurbochargedSquirrel > MonkeePuzzle 11/15/2016 at 21:16

3

You still want to rev match because it saves the wear on the clutch by not forcing it to deal with adjusting the speed of the engine.

AntiSpeed > 404 - User No Longer Available 11/15/2016 at 21:19

2

I guess that’s true but double-clutching on a downshift is pointless if you don’t rev match.

Flynorcal: pilot, offshore sailor, car racer and panty thief > Nauraushaun 11/15/2016 at 21:20

0

If you ever have your brakes fade/catch fire during a race you’ll get that engine braking helps with heat more the wear, and engine braking is crucial for shifting the weight of the car forward so that the front tires bite as you dive into a turn at high speed.

It’s also good for keeping oil moving around. Engine braking: It has uses for reals 

I’ve no idea why you’d double clutch any more than why some people think shifting without the clutch at all is helpful, racing or otherwise, but some people think it’s a thing. Honestly your anecdote about using it with a failing synchro is the only use I can think of as being practical. Quite genius actually. I don’t think I’d have thought of it. I’m old (see above) but not that old.

Double clutching might be additional wear of such little margin that it’s as useful as trying to keep your brakes cool while commuting to work. I’ve got a sequential gearbox so I’ve no choice, which I’m happy about as it compliments the exhaust nicely. Brap brap, minivans!

marshknute > Nauraushaun 11/15/2016 at 21:21

1

It’s not necessary from a mechanical standpoint, but rev matching makes the ride smoother.

Useful if you’re cruising in top gear and need to downshift for an overtake but don’t want the car to slow down from engine braking.

Nauraushaun > marshknute 11/15/2016 at 22:15

0

Ah, but rev matching has no relation to double-clutching. If you do need to adjust the revs while shifting, you can do it while the clutch is in.

Nauraushaun > MonkeePuzzle 11/15/2016 at 22:15

0

I agree, on both counts. But I see the point in rev-matching - otherwise the clutch has to match the revs, which does wear the clutch. And it’s smoother and quicker to rev-match.

I don’t see the point in the double-clutch.

Nauraushaun > TheTurbochargedSquirrel 11/15/2016 at 22:16

0

That’s right, but you don’t need to, so he’s strictly correct :)

Nauraushaun > Berang 11/15/2016 at 22:16

0

That makes sense. And is consistent with what I already felt ;) Thanks.

Nauraushaun > nermal 11/15/2016 at 22:17

0

I usually find that with reverse.

cluelessk > hike 11/15/2016 at 22:17

0

That’s not how it works. Using the engine to slow you down doesn’t do anything bad.

What’s your theory?

If anything it helps with fuel mileage. No fuel getting used vs having to idle the engine while using the brakes.

Nauraushaun > Flavien Vidal 11/15/2016 at 22:18

0

Oh that’s right. I am aware that braking too much on a long steep hill is going to make them fade. Ditto with too much fast driving all at once.

Nauraushaun > CB 11/15/2016 at 22:18

0

:<<<<<

404 - User No Longer Available > nermal 11/15/2016 at 22:18

0

Same thing in my Solstice. If I left it in a parking lot at -20C for the whole day, that truck transmission is super stiff.

Nauraushaun > HammerheadFistpunch 11/15/2016 at 22:18

0

pls respect me vin i’ll do it just 5 u

404 - User No Longer Available > TheTurbochargedSquirrel 11/15/2016 at 22:18

0

I think it’s the syncromesh, not the clutch itself.

Nauraushaun > My citroen won't start 11/15/2016 at 22:19

0

What do I look like A FUCKING PLEB TO YOU?!

Nauraushaun > Nauraushaun 11/15/2016 at 22:19

2

I’ll put my D in you

Nauraushaun > Flynorcal: pilot, offshore sailor, car racer and panty thief 11/15/2016 at 22:20

1

Good point. But it’s mostly for performance driving. Unless your brakes suck or your car is shit or you’re on a huge hill you shouldn’t need to save your brakes during road driving.

It’s no genius. I don’t know why I thought of it. I was just a fresh manual driver at the time. Guess Toretto’s words really stuck with me.

Brap brap :D

404 - User No Longer Available > My citroen won't start 11/15/2016 at 22:21

1

Only peasants without a sport auto drives in D. Ds is where it’s at.

Nauraushaun > AntiSpeed 11/15/2016 at 22:22

0

Double-clutching doesn’t make your car sound like anything ;) It’s the rev matching that does it.

You’re dead on about overheating brakes. Transferring the wear from brakes to drivetrain is silly, unless you’re trying to manage overheated brakes. Then it’s a worthy trade off.

Nauraushaun > AntiSpeed 11/15/2016 at 22:23

0

I think it’s pointless anyway - you can rev-match while the clutch is in. Double-clutching gives you more time to play with the throttle, but if you need more time just keep the clutch in a little longer. Pumping the thing isn’t necessary.

MonkeePuzzle > Nauraushaun 11/15/2016 at 22:35

0

plus rev matching is cool like smoking cigarettes in high school

unclevanos (Ovaltine Jenkins) > Nauraushaun 11/15/2016 at 22:35

0

I only double clutch for reverse or put it in first gear then reverse to avoid the crunch. Reverse isn’t synchronized on mine.

TheTurbochargedSquirrel > 404 - User No Longer Available 11/15/2016 at 22:41

0

The synchromesh handles the speed between the gears inside the gearbox (i.e. if the gears for 3rd are spinning at a different speed to those of 2nd). Without synchros you need to double clutch to match the speeds inside the box. What I am referring to is if you are doing 2000 rpm in 3rd and shift to 2nd without blipping the throttle and suddenly the engine needs to be doing 3000rpm and now the clutch has to pull the revs up. It makes for jerky shifts and unnessecary wear on your clutch.

Nauraushaun > MonkeePuzzle 11/15/2016 at 23:39

0

You mean like excessive drinking?

Nauraushaun > unclevanos (Ovaltine Jenkins) 11/15/2016 at 23:39

0

I usually go 4th to reverse. Worked in the Zs but I’ve had mixed results in the MR2.

Audistein > 404 - User No Longer Available 11/16/2016 at 04:29

0

What if we go full circle and drive in ‘M’ mode?

My citroen won't start > 404 - User No Longer Available 11/16/2016 at 09:58

0

not only do I have the D and the S, I also have the G.

ateamfan42 > unclevanos (Ovaltine Jenkins) 11/17/2016 at 08:24

0

How the heck are you using double-clutching to syncronize reverse? Are you trying to shift into reverse while already coasting backwards?

ateamfan42 > MonkeePuzzle 11/17/2016 at 08:28

0

Rev-matching isn’t about keeping the engine in the “sweet spot”.

Rev-matching is about bringing the engine to the speed it will be going once the clutch is engaged, before actually engaging the clutch. This prevents the engine (turning over at slower rpm) from loading the drive wheels during a downshift. Suddenly loading the drive wheels is like jabbing on the brakes for those wheels. If the car is being driven near the limits of grip in a corner, then the drive tires are going to lose lateral grip.

Rev-matching can also make for smoother downshifts by avoiding the engine loading effect, which can be appreciated by everyone in the car.

ateamfan42 > AntiSpeed 11/17/2016 at 08:35

0

On downshifts the main benefit is that it makes your car sound like a race car.

That’s not the *main* benefit.

The main benefit is that double-clutching allows a gear change without needing the synchromesh to do the synchronizing. This is of course necessary in unsynchronized transmissions, but is also helpful in synchronized transmissions with worn synchros, or where cold oil has slowed the synchro operation, or where the driver just wants to avoid wear and tear on the synchros. The last case is particularly beneficial when making extreme gear ratio changes, like 6th->2nd.

In addition, a properly executed double-clutch downshift gives you a rev-matched downshift for free. And the benefits of that are smoother shifts, slightly reduced clutch wear, and avoiding engine braking on the drive wheels (which is particularly important when cornering near the limits of grip).

MonkeePuzzle > ateamfan42 11/17/2016 at 09:07

0

K

TysMagic > My citroen won't start 11/17/2016 at 16:47

0

shameless self plug? you betcha

https://society6.com/product/i-heart-automatics_t-shirt#s6-6120105p15a4v77a5v18a11v49

TysMagic > Nauraushaun 11/17/2016 at 16:47

0

aggressive

Nauraushaun > TysMagic 11/17/2016 at 17:50

0

I did see that at the time. Considered buying. Will reconsider.