double clutching

[lospez54]

About 4 months ago i bought and 04 grey mazda3. And I've heard people talking about double clutching, but how do you actually do it?
thnx in advance (wrc)

 

[Alpinejwl]

I don't think that clutch is set up for double clutching....

 

[toucci]

Match the revs in between shifts by letting the clutch out in neutral and revving the engine. if done properly it keeps the syncros from wearing, and also lets you downshift faster and more easily. (IE: going into 2nd from 4th at 40 mph to haul some ass)

It's often used for downshifts and is often combined with a heel-toe movement to downshift while braking, using the toe of your right foot to hold the brake and your heel to blip the throttle.

 

[Dexter]

why is it called double clutching?

 

[toucci]

why is it called double clutching?

you disengage and reengage the clutch twice

 

[Mr. Win]

Double-clutching is usually reserved for those driving trucks or high performance racing cars, but anyone with a manual transmission can perform this simple feat.

For most manual transmission drivers, the act of shifting gears is a straightforward one. First the clutch is depressed, then the shifter is thrown into the next gear, and finally the clutch is released putting the car back into gear. All of this is usually done without thinking, at least after some practice.

But double clutching adds a third step into the mix. The shifter, rather than going straight to the next gear, makes a stop in neutral and then the clutch is released. This is to allow the engine to slow down (or with a tap on the gas, speed up when downshifting) so the transition into the next gear is much more smooth. The driver then depresses the clutch again and completes the shift into the target gear, and finally the clutch is released again, putting the car back into gear. It only takes a split second for the engine speed to match the speed of the gears, so the entire action is done very quickly as a fluid sequence of events.

Most modern cars, however, are equipped with devices called synchronizers that help to synchronize the speed of the gearbox with that of the engine. This effectively eliminates the need for double clutching. Some large trucks on the other hand have so many gears that synchronizers are inefficient, while race cars can squeeze out more power without them, making double clutching a fact of life.

There are times, however, that a normal car driver may want to make use of double clutching. Many manual transmission drivers realize the advantages of downshifting in slippery conditions. Rather than brake and skid, a car with a manual transmission can make use of the engine to slow down - thereby eliminating the possibility of a skid. But even with synchronizers, a driver trying to shift from fifth gear into second could have some trouble. In this case, double clutching by pausing in neutral and giving the engine a little gas to match speeds of the engine and gearbox, can allow such a drastic shift.

Some driving purists maintain that it's still the proper way to shift, and makes for a much smoother ride. It eliminates some of the jumpiness sometimes felt in a manual transmission car, and it decreases the stress on the gearbox. In any case, double clutching a skill worth having in emergency downshift situations, and not very difficult to learn.

i can google, yes i can

 

[Dexter]

you disengage and reengage the clutch twice

i will be in gear...need to slow down/downshift, disengage the clutch, press the brakes, blip the throttle with my heel, and re-engage the clutch.

is that not the same thing or am i missing something?

 

[RallyeRedSi]

Granny shifting not double clutching like you should!


Sorry couldn't help it

 

[FunkyBuddha]

Here come the F&F quotes LOL

Heel/Toe Dexter. Double clutch .you don't press the brakes at all. More for accelerating..if you ask me. Downshifting to a lower gear to pass somebody or what not...or to be in the right gear going into and coming out of a turn (if brakes are not needed for the turn).

 

[peepsalot]

i will be in gear...need to slow down/downshift, disengage the clutch, press the brakes, blip the throttle with my heel, and re-engage the clutch.

is that not the same thing or am i missing something?

You have to engage the clutch with the shifter in neutral for it to really be double clutching. This gets the gears inside the gearbox going the correct speed before it is put into gear, the action normally provided by a synchro.

this page helped me understand how it all works inside there
http://auto.howstuffworks.com/transmission4.htm

 

[Dexter]

oh...so for accellerating, though i will press the clutch, rev up, and then downshift.i dunno, it all seems to accomplish the same thing

 

[toucci]

oh...so for accellerating, though i will press the clutch, rev up, and then downshift.i dunno, it all seems to accomplish the same thing

the only difference is with double clutching you match the revs of the entire drivetrain, instead of leaving the part between the clutch and transmission freewheeling. I never double clutch my upshifts but I do whenever I have to skip a gear on my downshift or get the revs way up. I also have to do it to get the car into 1st while moving. Using double clutching you can get the car into 1st easily at over 20 mph.

 

[Pretzellogic]

Double-clutching, unless you drive a semi or an old car without syncros, is useless. Ignore what the movies tell you.

Now heel-toe downshifting. That IS useful, and fun too.

 

[lospez54]

how do you heel toe shift?

 

[t3ase]

how do you heel toe shift?

...It's often used for downshifts and is often combined with a heel-toe movement to downshift while braking, using the toe of your right foot to hold the brake and your heel to blip the throttle.

....

 

[BrianG]

I've read this before and was wondering something, but didn't want to sound like an idiot. Instead of engaging/disengaging the clutch twice, why not simply hold the clutch in and then rev the engine a little to bring the rpms up before letting out the clutch? What purpose does the "pausing in neutral while you let go and push in the clutch in again" serve? What is the difference between that and just holding the clutch in while you rev up or whatever?

I did a little Google-ing and couldn't find a quick answer to this point.

 

[toucci]

I've read this before and was wondering something, but didn't want to sound like an idiot. Instead of engaging/disengaging the clutch twice, why not simply hold the clutch in and then rev the engine a little to bring the rpms up before letting out the clutch? What purpose does the "pausing in neutral while you let go and push in the clutch in again" serve? What is the difference between that and just holding the clutch in while you rev up or whatever?

I did a little Google-ing and couldn't find a quick answer to this point.

the only difference is with double clutching you match the revs of the entire drivetrain, instead of leaving the part between the clutch and transmission freewheeling.

_____

 

[Brian MP5T]

Just try giving a quick shot of gas on a downshift as you are about to go from gear to target gear. It makes the shift faster and smooth.

 

[Pretzellogic]

If you have big feet, as I do, you can simply put one half on the brake and "roll" it to the right to goose the gas.

 

[peepsalot]

I've read this before and was wondering something, but didn't want to sound like an idiot. Instead of engaging/disengaging the clutch twice, why not simply hold the clutch in and then rev the engine a little to bring the rpms up before letting out the clutch? What purpose does the "pausing in neutral while you let go and push in the clutch in again" serve? What is the difference between that and just holding the clutch in while you rev up or whatever?

I did a little Google-ing and couldn't find a quick answer to this point.

The clutch disconnects the engine from the transmission. So if you want to get your gears set to the correct speed before popping into gear, then you gotta engage the clutch in neutral and set the engine rpm.
Whenever you put the gearshift into gear(regardless of your clutch being pressed), your transmission will be forced to spin at whatever speed the wheels are moving. Double clutching just get those gears going the right speed before putting it into gear(the same thing that properly working synchros do).
Read the whole article on how stuff works if you are really interested, it really helped me visualize everything that is going on.

Reaons someone might double clutch:
Your vehicle is not equipped with synchros
Your synchros are pieces of s*** or broken(like my second gear)
You are shifting to an extreme rpm difference that the synchros can't handle(downshifting two gears, etc.)
You are trying to go easy on your synchros