double clutch?

[fiznat]

Do you guys double clutch alot when you drive? I swear I love to do it.. every time I upshift I give it a little blip in neutral to bring it to where I need to be and it's all smooooth like butter. A friend of mine said, though, that it is sorta bad for the engine- and that "there is no sense in putting excess demand on the engine when the transmission is cheaper to replace if you screw it up.." I donno I just love doing it too much... I try to heel and toe upshift around corners while breaking down and all that... I donno Im kinda teaching myself as I'm driving around town. What kind of techniques do you guys use, and what do you think about double clutching as causing undue stress on the engine?

[C-Kwik]

For what reason would you be doing a heel-toe upshift? Sounds like you are describing a heel-toe downshift though, perhaps you are just using the wrong terminology. Downshifting is going to a lower gear, upshifting is going to a higher gear. In either case, double clutching is not necessary in a modorn car with working syncros. Double clutching was used originally just to be able to shift without a grind in earlier transmissions that had no syncros. The engine wear would be negilgible from doing it since it will not be loaded. Some argue that it will extend the life of your syncros, but why even have syncros then? I consider the transmission a wear item anyways...but that's just me. I heel-toe just about all the time. 50,000 of my driving on this car and I have noticed no wear in the syncros. I do it all the time to try and keep my skills sharp for the track.

[MAXIMUS Nismo]

i learned heel and toe from initial D. Tell me more about this double clutching please. how tos would be welcomed.

[C-Kwik]

i learned heel and toe from initial D. Tell me more about this double clutching please. how tos would be welcomed.

Car in gear moving, you press the clutch in like normal, movee the gear shift into neutral, pop the clutch out and back in quickly, put the car in the next desired gear, release the clutch again. This is for upshifts. For downshifts, you would blip the throttle somewhere in there...

[fiznat]

you're right, C-K... I meant downshift.. I get those mixed up sometimes cause "upshift" to me says "up-RPM.." but yeah that's wrong... my fault.Yeah I like to do the heel to toe/double clutch anyways, despite the syncros. I dont really care about keeping them perfect, it just seems like a better way to drive the car... it is smoother, and I feel like you can get better torque driving in that good RPM range... cool though, glad to hear other people do the same thing.

[MAXIMUS Nismo]

thanks for the info fellas. I got some practicing to go do.

[themadscientist]

you don't do it to save syncros, it's done to keep the engine RPMs in a sweet spot while you are shifting. If you don't they can drop below the ponit where the engine is making maximum torque. In a close race it can make a difference. I do it all the time out of habit.

[themadscientist]

why do you say that? That is is exactly why I do it and exactly what it does.

[themadscientist]

yeah you could try supporting the statement! To hard for you?

[themadscientist]

I am not contendin the synchro thing, I blip the throttle to keep the RPMs up so when the clutch comes off I am still in the sweet spot. It works, whether you chose to acknowledge it or not has no bearing on that.

[themadscientist]

and your alternate method would be? Your suddenly so talkative please share.

[themadscientist]

As I wrote yes it is, I should have said "why I do it", I claim only marginal typing abilities. Now would you not agree that blipping the throttle between shifts keeps engine RPMS up. If you have a better way say so, I would honestly like to know. I have a CA18DE with no grunt, and a lightened flywheel with big 16" wheels and winding it out is the only way to keep it from bogging on the 1-2.

[themadscientist]

who is deleting my threads? why?

[C-Kwik]

Not too hard, too pointless. You're asking me to prove that the sky is blue.

Double clutching serves one purpose: To reduce wear on your syncros. The fact that you happen to be shifting in the engine's sweet spot is irrelevant.

This statement is not true on older cars that do not have syncors or cars where syncros are completely shot.

But all in all, if you have good syncros, K-car is right. Plus it's slower. You can upshift and heel-toe downshift without double clutching. They are two different things. It's faster not to double clutch. Frankly, double-clutching is like shifting twice. So you lose all that time accelerating. And as far as heel-toedownshifts, I row through gears quite quickly on a track. I care not to dilly-dally with pressing the clutch twice just to extend my syncros life. Why even have them then. When they take a crap on me, maybe I'll consider it.

[WhtTrshPunk]

Quote »Now would you not agree that blipping the throttle between shifts keeps engine RPMS up[/quote]

Of course it does, but you don't need to double clutch to do it, you can blip with clutch in between gears. Double clutching just takes more time and puts you between gears longer, and when you're not in gear, you're not gonna go any faster

[Bubba1]

I'm with C-Kwik. Double-clutching a fully synchronized 240sx is unnecessary. As long as you're not beating the living crap out your car, you're not significantly helping your synchros by doing it. But you're also not really hurting them either. So if you want to feel like a racer, do it and have fun. Just realize you would be quicker if you didn't do it.

[issanni]

"On the racetrack where you're operating close to the tires' limit of adhesion, a downshift without a blip (either by heel-two, or double clutch methods) can use up all the traction of the rear tires and spin the car in the straight-line braking zone. Even for a car with a synchronized transmission, a blip before clutch release is mandatory." Furthermore, "In shifting gearboxes with synchronizers, the function of the blip is to smooth out the clutch engagement after moving to the next lowest gear. Since most racing transmissions do not have synchronizers, the blip not only cushions the clutch engagement, it also allows you to synchronize the speeds of the input and output shafts."

-Carl Lopez, Skip Barber racing school instructor and author of "Going Faster, Mastering the art of race driving"-

Not saying anyone is right or wrong, but that's straight from authoritative sources. But in their own way, both K_car and themadscientist are correct in their statements. Basically those two statements I quoted are saying that for normal street driving, 'blipping' the throttle is not necassary, but it is necassary on the track. Also, I don't know where people are getting double clutching for upshifts. I mean, yea, it was mentioned in that fast and furious movie (that right there should raise the ol' BS flag), but the whole principle behind double cluthcing is to blip the throttle..therefore raising RPMs....why would you want to raise the rpms on an upshift? As in if you shift at 4000rpm, then blip the throttle, then egage the clutch at 5000rpm??? why? Double clutching is a downshifting method.

[not_a_porsche]

"On the racetrack where you're operating close to the tires' limit of adhesion, a downshift without a blip (either by heel-two, or double clutch methods) can use up all the traction of the rear tires and spin the car in the straight-line braking zone. Even for a car with a synchronized transmission, a blip before clutch release is mandatory." Furthermore, "In shifting gearboxes with synchronizers, the function of the blip is to smooth out the clutch engagement after moving to the next lowest gear. Since most racing transmissions do not have synchronizers, the blip not only cushions the clutch engagement, it also allows you to synchronize the speeds of the input and output shafts."

-Carl Lopez, Skip Barber racing school instructor and author of "Going Faster, Mastering the art of race driving"-

Double clutching is a downshifting method.

"Double clutching is a downshifting method. " is not what the above paragraph is saying, you are extrapolating that.

It is primarily used during downshifting, but if you want to be gentle on your transmission you can do it on either up or down shifts.

[Bubba1]

Not a porsche: Carl Lopez IS talking specifically about downshifting in a track environment. Read the first line. There's no reason to double clutch an upshift in any car, even an unsynchronized one, unless perhaps if you blew the shift. All it does is waste time.

[not_a_porsche]

I fail to see in that paragraph where it says ONLY for downshifting.

[Bubba1]

What makes you think he was NOT talking about just downshifting? His first sentence did discuss "downshifting", not general gear changes, not upshifting. Perhaps you could explain why one should double-clutch an upshift?

[themadscientist]

I continue to notice errors in what I said on my initial post, no coffee, calling in my get of jail free card. After thinking about the way I drive I don't double clutch at all. I keep the clutch down and blip the throttle as I am engaging the next gear and release the throttle. I don't think that could be called "double clutching".

[issanni]

Perhaps you could explain why one should double-clutch an upshift?

That's what I'm trying to get at. Maybe I worded it incorrectly by stating "double clutching is a downshift method", but I just don't see any reason whatsoever to double clutch on an upshift. I would think that if you double clutch on an upshift, the input shaft would be spinning faster than the output shaft since the car is accelerating...at least when you double clutch to downshift, you are slowing down. Not sure if I explained what I mean correctly, but anyone may correct me as they see fit.

[APEXi240]

Actually, I was told (isn't this how every wrong response starts out) that cars that use cable shift linkage, as opposed to a rod type should double clutch on high speed upshifts because the cables in the shift linkage may have a tendency to get tangled.

However this would not apply to 240s.I like the scientist just rev-match on downshifts and do not double clutch. Why be an a**hole pushing the clutch down constantly when you have syncros? You payed the money for them, use them.