Since I don't have access to the racing forums, I thought the next best place to post a shifting question about my coupe than in the coupe forum!

So, how bad is this for my transmission?

By Double clutch- I'm referring to the quick press of the clutch before shifting.

I.e. around 800 rpms before my shift, I give the clutch a quick depress get the rpms up, let go (real quick in and out) it should be just about red line, and then throw her into the next gear.

Every time I've done I'm usually pulling a lot harder in the next gear, than the fella next to me.

But.... This has to be harsh on my transmission,

Opinions?

 

double clutching is for old trucks that dont have syncros, dont necessaraly understand what ur doing

 

Yeah maybe I'm using a misnomer.

Its probably a bunch of bull anyhow.

-
I just tap the cluth at around 5.2k, the rpms shoot up, I'm just about red line then I shift normaly.

-BM

 

off topic, but I can't post on the racing forums anymore either, why?

 

What you are describing is not double clutching. Actually it's not even a real technique anyone really uses.

Double clutching involves using the clutch twice on each shift, but you press the clutch, shift to neutral, let go of the clutch and push it back in again, shift tot he next gear and release. The technique is used to match the speed of the gear to the dogs so you can actually get the car into the next gear. This technique on NOT needed or does it serve any logical purpose in a modern transmission since we use syncros now. Nor would it produce better results. An 800 RPM momentum shift is rather small. A 2000 RPM momentum shift is going to put a bigger kick into it. As long as the tires and clutch hold you'll gain a slight increase in overall accelleration. Keep in mind this kind of thing does increase driveline shock and you may end up with a transmission case full of parts one day. With 260-270 lb-ft of torque, 3500 lbs, and a 30 lb flywheel, ther ecan be a lot of driveline shock. I broke a tranny and a diff in a car with 2500 lbs, 125 lb-ft of torque and a 20 lb flywheel.

What you are describing has no real purpose as well. What you are doing is actually disengaging the mechanism that accelerates your car(the engine) momentarily. To me, this would take away some of the time you would spend accellerating. While a slight kick from the increased RPM's might make up for some of it, the law of conservation of energy would tell me it's not. There would be less torque at that RPM, and since there would be some slippage of the clutch just as you disengage and re-engage the clutch quickly some of the energy here would be converted to heat. It would seem to me you are actually wasting energy. You could just as easily get a similar effect from a single clutch activation by holding the gas pedal down between shifts. This would at least be done during the time it takes to shift anyways, and provide a slight kick that could aid accelleration.

 

Double clutching should only be used in concert with heel and toe downshifting, which is a high performance/racing technique for putting the car in the proper gear to accelerate out of a turn. But it's mainly for cars that lack synchromesh gearboxes, which the G (and pretty much all modern cars) has. I don't understand what it is you're doing or accomplishing with what you describe. Is this on an upshift or downshift? Dbl-clutching on an upshift is never necessary, and is a time waster. You can't be doing your acceleration or your clutch and tranny any favors.

 

Try driving a car with no syncros or worn syncros. It is required when shifting up or down.

 

I have driven several, including Formula Ford racing cars, and have never needed to double-clutch on upshifts. Downshifts, definitely, but upshifts, no.

 

You lads are absolutely correct. No double de-clutching on this car with its synchros is required, or even sensible. A single declutch by using the heel and toe "blip" is a good idea on the downshift when you are driving aggressively and find that in addition to braking you need to get back on the throttle hard for acceleration as you come out of the turn. But in street driving that is pretty rare. Maybe in some spirited fun on some twisty canyon roads. On the track it is standard fare multiple times per lap.
On the nonsynchro crash box you absolutely need to rev match, but even then you don't have to double de-clutch. It is smoother but you don't have to. If you are real good at matching the revs, it is faster and still smooth to do the single.
On the upshift you just upshift. No fancy anything. The revs naturally are falling as you engage the clutch and remove the power, and then upshift to the higher gear which with the higher gear's drive ratio will naturally engage at lower rpms, especially if you have a lightweight flywheel that falls off faster than a stock one. You don't want to be blipping the throttle to jack the rpms up just to drop the tranny into a higher gear!

 

Race transmissions that do not use syncros are built differently. The dogs fit much looser so they are easier to mesh without syncros. OEM trannies use very tightly fitting dogs so that it remains comfortable to drive with little noise when getting on and off the throttle. The factory cars I've driven without syncros all needed a double clutch to get into each gear regardless of up or down shifting.

 

Sounds like you used to own a Celica

 

1983 GT-S actually. Good call.