So why not just tap the accelerator as you change gear to get the RPM up instead of dropping the clutch twice and putting it into neutral and then into gear if that makes sense?

Thanks

 

Some cars respond to this better than most, bliping the throttle going down the box.

 

Double de-clutching is the technique of bringing the gear cluster up to the speed required to synchronise the rpm of the engagement dogs. used mainly on 'crash' gearboxes ie no synchromesh (older racing boxes and old lorries!) Clutch down, gear into neutral, re-engage clutch, bring revs up to required rpm, clutch down, into the lower gear, re-engage clutch. It has to be done quickly to be effective. Needs lots of practice. Used to do it a lot in my youth but with modern synchromesh boxes, it's not really required and is a dying art.
Just blipping the throttle when changing down brings the revs to what is needed for the lower gear but of course does not synchronise the revs of the engagement dogs.

JohnD

 

Double de-clutching is not to be confused with rev-matching.

They can be used together, well in rapid succesion, giving a wonderful melody as you brake hard and down shift from 4th to 2nd for a tight curve.

Even a 'box with synchros can benefit, even if only in the lifetime of the synchro cones.

Rev-matching should NOT be a dying art! Braking hard into a corner, grabing the correct gear for the exit, if you fail to rev-match, the engine braking can/will get the back end sliding.

 

I got the two confused, sorry.

 

just learn how to heel and toe this is the best method of going down the box double de cluching as said is for your older cars.

 

Its clutch, neutral, rev, clutch and in, well thats how the army taught you

Tony

 

Double de-clutching can however help with sustained rev gear changes since it slows down the actual gear change
It isnt necessary with modern cars but can be a useful teaching aid

 

another vote for heel and toe - ive managed to get it spot on with the scoob. When you get it right its awesome!

 

Yes, heel and toe is essential for proper down changes in racing and fast road driving. Big problem is that most brake and accelerator pedals are not matched for height and distance apart when the brake is being depressed and I've found the Subaru accelerator pedal not sensitive enough for accurate revs when doing it.

JohnD

 

I think i may have been misunderstood by some. What i mean is when changing gear you can double declutch, what i'm trying to understand is how this method is anything different to just tapping the accelerator when changing gear while the clutch is disengaged. Guessin this:

"Just blipping the throttle when changing down brings the revs to what is needed for the lower gear but of course does not synchronise the revs of the engagement dogs."

Can double declutching be used on up and down gear changes?

Thanks

 

The "tapping the accelerator while the clutch is engaged" method is often called a "false double declutch".

That's pretty much it. A proper double declutch will accelerate the gearbox input shaft before you attempt to go for the lower gear. However as has been said it's a pretty pointless exercise on a modern synchromesh gearbox. Rev matching is all you need to downshift smoothly.

There's no point/reason to do it on upshifts.

 

double de clutching - whats the point if you want a fast gear change? thats for trucks!
you can double declutch but for what reason & gain?? if you really must then yes blip the throttle to aid engagement of the next gear.

heal and toe to blip the revs up on down shifts to match engine speeds- yes. I even do that in my Audi A4 diesel!

and nothing wrong with left foot braking either!!

 

Yes it can. But again, it's really only needed when thre's no synchromesh (or when the synchro is knackered - it's happened on quite a few Scoob boxes!)
Double-de-clutching when changing up brings the revs down to the reqiured figure for the higher gear ie you allow the revs to drop and not blip the throttle.
It's common with most gearboxes that trying to engsge 1st much above walking speed, is not always easy. In this instance, double-de-clutching (with a blip) cures the problem.

JohnD

 

Double declutching is rather redundant with a synchro box, still works well with dog boxes though where a simple throttle blip will not work.

 

Thanks, makes more sense now.

What year did synchromesh fade out?

 

Think you mean when did synchromesh come in

Tony

 

Yeah that's what i meant lol.

Thanks