Being an ancient fellow, I've been brought up to double de clutch/heel and toe.
With a new Sti, I figured that this will overcome the lag at low revs. I had some racing tuition a couple of years ago however and my tutor was very scathing about double de clutching as have others I've spoken to.
What's the consensus of opinion ?

 

AFAIK double delclutching was only used because very old car had gearboxes which had no syncromesh and you had to shift into neutral before selecting the next gear. 0-60 in 5 seconds would be closer to 10 IMHO . No point in a scoob just be precise and accurate.

 

OK, this isn't double de-clutching but is the gear change not smoother if you blip the throttle mid down-change? (i.e. whilst the clutch is fully depressed and before raising). Would that put additional wear on the clutch?

 

Andy Walsh still teaches the technique on his driving days (in conjunction with heel / toe braking). His courses are mainly aimed at improving your driving technique on the road. I would agree there is no real mechcanical need to do it, but it can make your driving much smoother - the aim of what Andy is teaching. I would recommend a day with Andy to understand from someone who knows how to do it properly. Details at 1st Lotus

Chris

 

Make the engine speed match the gear speed. Simple (in theory). This may mean blip the throttle on down change to raise the engine speed as the lower gear will need to match the engine speed.

You can move the gear lever from gear to neutral without using the clutch by just matching the engine speed (put some pressure on the lever to pull it out of, 4th for example, and just let the revs drop and it can slip into neutral easily). Doing this going up a gear is somewhat more difficult and if you get it wrong you can damage the gearbox (hence the reason for having a clutch).

BTW this applies to just about any normal manual car.

[Edited by Dracoro - 12/30/2002 9:43:20 PM]

 

Blip your throttle as you change down

Keeps the car more balanced as it stops engine braking.

 

But surely just bliping your throtle isnt double delclutching ?
I blip my throtle to keep the revs up but delclutching is used to match the gear speeds on old cars and lorries that didnt have syncromesh (as chrisp said )
I dont think that blip-change is the same as change into neutral-blip-change into gear...or is it just me ?
But i do agree bliping does help to create a smoother drive

Andy
Edited to say that looking at the posts i can see others have said that its not delclutching also

[Edited by Attu - 12/31/2002 1:22:17 AM]

 

Clutch, neutral, rev, clutch and down gear, thats double clutching.
You may find the easiest way to improve downward gearchanges is to brake then change gears as i dont seem to have any problems with my scoob doing this (but first gear can on alot of cars be a problem).

Tony

 

I teach advanced (police roadcraft) driving with the ambulance service and until about 5 years ago we taught double de- clutching but I didn't like or agree with the need for it with modern gearboxes. We now teach "sustained rev gearchanging" or blip between changes as it is crudely described above. Do the braking to the required speed then set the revs to what they are going to be for the gear you are moving to whilst changing the gear, this gets the vehicle settled and ready for the corner prior to turning the wheels with no sudden deceleration on letting the clutch up which can lead to oversteer.
Ie, if you leave your foot on the gas just holding your speed in 4th (not accelerating or de celerating) and leave it exactly where it is while you change gear the revs should be spot on in 3rd when you take the clutch up. Sorry for the long winded answer but it is difficult to explain in words on paper,

 

If you keep the throttle position constant while changing gears surely the revs will just spike when dropping a gear? Say you're at 3000rpm in 4th, keep the throttle where it is and drop to third - your revs without additional throttle should jump to just under 4000rpm (depending no how quickly you change gears of course). Or am I missing something?

 

Yeah Swan, but that is what you want the revs to be when you let the clutch out in 3rd anyway, therefore giving you a super smooth gear change.

 

I have to do it for my dogbox - after a while becomes second nature - only thing I can't really do is heel-toe breaking - but that will come along in time....

 

If you blip the throttle on downchanges (and get it right, i.e. match the revs to the target gear) then it actually reduces wear on the clutch since both sides of the clutch will be travelling at the same speed rather than the clutch transferring the momentum of the car to the gearbox to bring the engine up to speed.

Really easy to do on the scooby with a little practice, since the engine is so responsive. Some cars are a PITA to do this with, it's not so much a blip on the throttle as hold the throttle down for a sec while braking since it takes so long for the revs to pick up.

 

Isn't it brakes to slow and gears to go?
Brake to required speed then select gear to go so, in effect, you can brake from 70mph to 20mph on a dual carraigeway approach to a roundabout and then bob it straight from 5th into 2nd and plant it again

wears your pads out quicker but pads are cheaper than the strain engine breaking puts on engine/gearbox

 

In the bad old days before synchromesh had been invented it was necessary to match the speed of the dogclutch for the target gear in the gearbox with the gear on the mainshaft to allow it to engage and also to do it without the nasty noises. It was necessary to use a combination of double de-clutching to allow the engine to match the gearbox mainshaft speed by de-clutching to move the gearchange to neutral,letting the clutch in while the gearchange was in neutral and using the accelerator to control the engine speed. The clutch would then be depressed again and the gear selected. The clutch would then be engaged to continue in the target gear. This was especially necessary in commercial vehicles with big gearboxes and lots of inertia internally. as we now have baulk ring synchromesh this procedure is not necessary although many people take a pride in being able to do it and a skillful driver can change gear as quickly as a normal change, and if done properly it will save wear on the synchro baulk rings.

You can of course change gear without bothering to increase engine revs on a down change if you wish. If you are really driving hard and entering a corner close to the limits this is unwise because as you let the clutch in you can easily break the rear wheels away and it will at least de-stabilise the car. It is obviously better to increase the engine speed as you change down to avoid all this. As was mentioned it certainly will not wear the clutch out if you engage it with the engine speed matched to what it would be in the lower gear. All this used to be expected of a skilful driver in earlier days. Even now though, it is very satisfying to do a double de-clutch down change holding the revs at the correct speed so that you get a seamless gearchange using the heel and toe method and all in plenty of time to be able to enter a corner fast feeding the power on smoothly to balance the car in the bend. It is also the way to a fast lap time.

Les

 

I have always blipped on my downshifts since I learnt to drive!. Initially it was to get my Mk2 Escort to sound like a POO rally car, but after a while it became habit.

Dont do it on the track though as the brakes stop you too quick and there often isnt enough time.