Hey guys, im pretty new here and i had kind of a easy question. What exactly is double clutching, and what is the point of it. I just power shift when im racing, but i have heard of people double clutching. Thanks guys

 

Do you mean double clutching?

 

if u mean double clutching, only time ive used it is when, the gear had bad synchros and i couldnt get it in, so if you double clutch it helps the gears match up better for shifting. And i know some heavy duty trannys you have to double clutch i believe, im not positive.

 

synchros do it for you. ricers talk about it cause its 'cool'.

 

i usually do it when downshifting more than a gear

you put the clutch in and put the car in neutral
rev up the engine
push the clutch in and put the car in the lower gear

it gets rid of the jerk say if u were to just downshift from 6th to 3rd at 65mph

 

I heard this double clutching thing also. But never really knew what it was or if it was useful. So your sayingt hat its the samething as Rev matching?

 

I saw it on The Fast and the Furious, then that big ole ugly American car burnt rubber and popped a wheelie but luckily the Supra had NAWZ and he double clutched so a train almost hit them both and the Supra won.

The End.

 

I thought it was an RX7?

 

No the RX-7 was Vin Diesels older car. Paul Walker had the 10-second Supra remember it was all burnt up then they rebuilt it. These guys live their lives a 1/4 mi at a time.

Back to your regularly scheduled program.....

 

Rev matching is part of double clutching. Clutch in, neutral, clutch out, rev match, clutch in, shift, clutch out. Seems like this topic comes up every month or so.

 

Can't you just push in the clutch and rev match while you downshift. Me personally I just give her hell, never did have an automatic vehicle.

 

If you do that you only get half the benefit. You're engine will be at the right speed, but the input shaft will be moving too slow so you'll still be making it hard on synchros.

 

Oh yeah you're right. I think the RX-7 should have raced the Supra...I wonder how much NOS that movie sold?

DamanZ28 I think most of the time heal & toeing will accomplish the objective but double clutching is kind of fun if you have the time before entering the corner.

 

When you are driving a tractor trailer with no syncros in the transmission. Or if you are driving an import with lots of stickers, NAWZ, and Boost.

 

The T56 can be a bear to get into second when cold; that is the only time I do it. It just allows you to get it in to gear useing less force by matching the input and output speeds of the gears.

 

If you do that you only get half the benefit. You're engine will be at the right speed, but the input shaft will be moving too slow so you'll still be making it hard on synchros.
>>>>

How will it be moving to slow, once the clutch is disengaged the clutch disc will no longer be spinning at the engine rpms anyway?
So the input shaft speed will be slowing down everytime you depress the clutch.
No matter how many times you clutch it.

Clutch in = slow disc speed = slow input shaft speed.
clutch out = clutch disc speed = engine RPM = input shaft RPM.

The only time the input shaft speed can be increased is when the clutch is out.


I rev match my auto for quick downshifts and tight high speed corners.

Who says autos can't be fun?

 

Let's say you're downshifting from 6th at 2000 rpm to 4th at 4000 rpm. You push the clutch in, shift to neutral and release the clutch. Now the engine/flywheel/clutch disc/input shaft are all locked together. Now you rev to 4100 rpm and push the clutch in. The clutch disc/input shaft are no longer locked to the engine speed, but in the time it takes you to shift they only fall back to 4000 rpm, or very close to it. You let the clutch back out and the engine/flywheel/clutch/input shaft/output shaft/driveshaft are all spinning at 4000 rpm like they should be.

If you had just rev matched instead of double clutching, the synchros would have had to accelerate the input shaft and clutch disk from 2000 to 4000 rpm before it finally goes into gear. By reving to 4100 rpm instead of 4000, you allow time to push the clutch in while the input shaft slows down.

 

Rev matching an auto? That cant be good. I can kinda guess but could you explain how and why you do this?

 

I see, but, instead of "double clutching" you should be able to "throttle up" or "rev match" the engine rpm with the accelerator and raise the rpm up to make the down shift smooth and silky instead of just being hard and jurky.
I do see your point, maybe it would be easier (lol) to goto "neutral" with no clutch depressed and then rev match it for the gear of choice.
That way you bypass the double clutching.

You should try driving around in a M6 car ( or just a manual trans ) and not using the clutch at all after first gear by rev matching the rpm for the gear up or down shift.
Try getting a manual car to move without using the clutch ( gotta use the starter to get it to roll and fire the engine then it's all fun from there.

If you can get that down in a manual then the auto is very easy.

I've had clutches go out on me a few times ( different cars ) and had to use this method of shifting just to make the trip home.

Down shifting without the clutch would be my favorite thing for a manual trans.

You have to know where the engine rpms needs to be for the given gear selection you make based on the mph your going. ( lots o practice, not going to make you any faster though ) Big fun!

Yes, upshifts and down shifts can be made without using the clutch.
Using the clutch will and can help speed up the up shift as you will have to wait for the engine RPM to drop for the next shift to "sync" the gear and rpm without using the clutch or grinding the gear.

 

8-Pack:

here is the link if you want to read all 3 pages...
https://ls1tech.com/forums/showthrea...=292644&page=3


Basically, here's your answer. ( cliff notes )
If it's good or bad on the trans I have no idea.
Maybe someone else can add some better info as I'm not really a ( auto trans guy lol )
BTW, I don't do it unless I need more control.

I'm the second owner of my car, I got it with 21K on the OD and I have no idea how it was driven before I bought it.
At 30K the trans bought the farm and I was just leaving a 4 way stop ( just normal driving ) and BANG.
No more forward gears.
I really didn't do much "rev matching" before it blew.
The trans was rebuilt ( OEM warrenty ) and I "rev match" the downshifts several times a day now, mostly for fun and the tighter "feel".

Got me, I just know sometimes I like it to work like a manual trans that I'm used to driving when I need it.
>>>>>

Originally Posted by darrensls1formula
I would think whenever you have a track that has twists and turns the manual cars will do better because you can downshift for a turn and not have to wait for a computer to kick the transmission in the right gear after the turn when you go WoT again. It may feel just as fast but I'll bet a clock would tell a slightly different tale. I'm no autocross/road racing expert so that's just a guess as to why they are better.

I don't think sixth gear helps them that much in road courses but it definately gives them better gas mileage on the highway getting to the road course.



I would think whenever you have a track that has twists and turns the manual cars will do better because you can downshift for a turn and not have to wait for a computer to kick the transmission in the right gear after the turn when you go WoT again.
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I see, but I have noticed if you rpm ( use the throttle ) match the gear for the downshift ( just as you would in a manual for heavy decel ) mph you don't have to "wait" for the computer to make the downshift. It just goes into the gear acting very much like a stick would do.
It will bypass what the computer "will do" and just downshift the gear instead of "waiting".
Maybe it's just my trans or the way I drive/shift/throttle it

I did have the trans rebuilt and the guy did say he put a shift kit in it but I think he was full of it because a friend of mine said it would shift alot harder if it did have a kit.

I do know what your talking about when you say "wait" because it will take "time" if you let the computer make the downshift without rpm matching the gear.
Mine will bypass what the computer "will do" and just downshift into the selected gear ( depending on mph and gear selected, obviously if I select 1st gear at 70 MPH the computer won't let it go into 1st until the mph is within the mph that I can get out of 1st gear at or below redline ) if I "punch" the gas as I downshift the gear manualy.


computer to kick the transmission in the right gear after the turn when you go WoT again
>>>
You can hold the manually selected gear or shift up (manually) as needed for the corners.

I see what you mean about 6th unless the M6 is running a really high rear gear then it could utilize 6th.

Maybe my car/driving style is just nutz.

I don't know, But I know I have a headache now lol.