Double Clutching

[vivalaham]

im in an argument with my friend about the double clutching method.
he believes that double clutching will increase top end speed
i believe otherwise


which one of us is right and can you give a brief explanation why?

thank you
ty

[KiwiBacon]

How could double clutching affect top end speed?

For the vehicle to attain any speed, your foot must be off the clutch. How you change gears only matters to acceleration.

[AudioGuy93DelSol]

Double clutching is for down shifting. It's to speed your transmission up to where you're RPM's will be in the lower gear to make it easier to go into gear. This was necessary on old, unsynchronized transmissions but can be helpful if your transmission is old has has trouble going into gears. Double clutching on up shifts actually makes it harder to go into gear because it keeps your trans spinning close to red-line RPM, then you try to slam in the next gear which is significantly lower on the RPM band. Either way, Kiwi's right, it's got nothing to do with top speed. Unless you mean a higher trap speed, in which case it will decrease it.

[GreyGoose006]

it is useless in anything but a 1930's mac truck

[ShadowWulf2K]

Double clutching means: stop getting your info from The Fast and The Furious. Why didn't anyone say this already?

But seriously, double-clutching is a downshift technique you wouldn't use on a production car anyway.

[beef_bourito]

heel-toe is used to allow smoother downshifting but that's only usefull in a racing situation (as in a track, not a straight line) and that's about as close you'll get to double clutching with a modern vehicle.

[KiwiBacon]

Originally Posted by GreyGoose006

it is useless in anything but a 1930's mac truck

Trucks, tractors, anything with either a heavy duty gearbox or worn out synchros.

Definitely a dying art.

[bobss396]

Originally Posted by KiwiBacon

Trucks, tractors, anything with either a heavy duty gearbox or worn out synchros.

Definitely a dying art.

I don't know, I know a lot of people that supposedly know how to drive a stick, but they must have learned on school buses. They shift like somebody's grandmother. I had to teach my sister inlaw, she hadn't driven a stick in years and was doing bizarre things.

Bob

[BeteNoir]

Double clutching or more properly double de-clutching is an obsolete techique that is no longer used in racing. Prior to synchromesh transmissions it was necessary to match engine speed to drive shaft speed in order to engage the transmission gears during a down shift without grinding them. With a synchromesh trans the technique is no longer necessary and increases the time necessary to downshift.

Heel and toe is another out of date technique that is no longer necessary. What is necessary is to properly match the engine speed to the drive shaft speed as the clutch is engaged. This can be done very quickly without the convoluted ankle twisting required by the heel and toe technique.

In modern race cars, sequential gear boxes are used and no clutch is necessary. In many cars a paddle shift allows the ignition advance to be retarded momentarily while the gear shift is made to reduce stress on the gears.

A really good race driver can shift a non-synchro trans without the use of a clutch simply by properly matching speeds. So can most semi drivers.

[Black Lotus]

Originally Posted by BeteNoir

Heel and toe is another out of date technique that is no longer necessary. What is necessary is to properly match the engine speed to the drive shaft speed as the clutch is engaged. This can be done very quickly without the convoluted ankle twisting required by the heel and toe technique.

Really.
How do you propose doing that without blipping the throttle for a downshift?
I'd like to know since my Lotus is sort of a bitch to heel and toe (no room in there).

[Moppie]

Originally Posted by Black Lotus

Really.
How do you propose doing that without blipping the throttle for a downshift?
I'd like to know since my Lotus is sort of a bitch to heel and toe (no room in there).

You must have bloody big feet, I remember an S4 Esprit being one of the easiest cars to heal and toe. Mind you the wheel was on the proper side in the ones In driven.......

[Moppie]

Originally Posted by BeteNoir

Heel and toe is another out of date technique that is no longer necessary. What is necessary is to properly match the engine speed to the drive shaft speed as the clutch is engaged. This can be done very quickly without the convoluted ankle twisting required by the heel and toe technique.

In modern race cars, sequential gear boxes are used and no clutch is necessary. In many cars a paddle shift allows the ignition advance to be retarded momentarily while the gear shift is made to reduce stress on the gears.

A really good race driver can shift a non-synchro trans without the use of a clutch simply by properly matching speeds. So can most semi drivers.

As BL said, how exactly?
And not all race cars use sequential gear boxes, in fact the vast majority still don't. Its still very expensive technology relegated to a limited number of single seater classes and WRC.
Heal and Toe is by no means an out dated technique, and is often used with sequential gear boxes. Have you seen some pedal box camera footage of a WRC car?

Engaging the clutch does one thing, it disengages the drive to the wheels.
It is generally done to facilitate gear changes, but has other uses.
For example stopping the car from stalling, stopping the engine from compression locking the drive train, or reducing applied torque to limit wheel spin.