No. That isn't double clutching, that is rev matching. You are fine.

 

I would not recommend power shifting i.e. not letting off the gas. You may get slightly better times, but if you plan on keeping the car, it's definately not a good idea.

Double clutching is good to know, but with the synchros today, it's not really necessary, unless you're going into first gear or something. Single clutch downshifting is fine, and for the normal driver, should be faster. Either way, just make sure to rev match when you down shift.

Here's a good thread about how to launch your car
http://forums.bimmerforums.com/forum...ad.php?t=47538

 

From a stop you will get the feel for it. You want to launch as fast as possible without tire spin. Take it to the redline and shift as fast as you can, thats about all I have to say.

 

noob here
what's rev matching? how do you match the rev to the speed?

 

I just went out for a little test drive...

I believe that the synchro shifting (downshift and pop the clutch) is actually a little faster than double clutch downshifting. Probably faster by about ~0.1 seconds.

But, double clutching is MUCH smoother, there is no jerk when you shift, and the car feels more responsive. Dunno, with some practice maybe I can get the double clutching faster.

 

you don't need to double clutch a Z!

just practice matching your revs smoothly. .. after that, practice heal-toe'n .. that will get your footwork set.

practice practice.. forget the double clutch.

 

My dad taught me how to rev match/double clutch whatever it is being called, when you bring it to neutral and rev then put in gear. He told me that older cars I assume older meaning 60's-70's you had to do this with. With newer cars, there is know need for this. Not sure if he is right, but I say just shift the car and practice, practice, practice.

 

another difference between "rev-matching" and "double clutching": double clutching will wear out the clutch twice as fast.

I really tried to figure out a way to post this w/o sounding like a smart a$$, but I came up empty.

 

Where'd you get that from? Did someone actually tell you that, or did you make it up.

This is FALSE

Go ahead and sound like a smart ***, if you're at least going to make sense.

 

seriously. When my dad was a truck driver driving semi trucks, I knew the maintainance/repair guys and they would complain about the guys that would double clutch and how they had to do work on the transmissions twice as often because they would burn the clutch faster.

My bad if the information I was given was incorrect.

 

Maybe when you mention double clutching, you're thinking about something different than I am.

Didn't mean to be harsh in my post. It's not like I know everything either.

 

double clutch - clutch in, neutral, clutch out, clutch in, in gear, clutch out. you use the clutch twice for each gearshift ergo you wear out the clutch twice as fast as rev-matching.

that's why I said I was looking for a way to not sound like a smart-a$$ (double-clutch, twice as fast)


like I said, this was just information I got from semi-truck mechanics but I imagine it would transfer over to cars.

If you thought I was talking about rev-matching wearing out the clutch, I wasn't. rev-matching is easier on the clutch and transmission as the parts don't mash or jerk together.

 

Double clutching isn't needed for modern cars, but in older cars and trucks, the synchros are either a primitive form or already worn. With these semi-trucks, if you didn't double clutch when you downshited, you wouldn't be able to get into a lower gear.

The clutch will only be excessively worn when you transmit power through the clutch or ride the clutch on a daily basis. Let me explain what I mean by transmitting power through the clutch.

When you press the clutch all the way in, you can rev all you want and not damage the clutch. When the clutch is fully engaged, when you step on the gas, the power is transmitted to the wheels. When you release the clutch and hold it at the engagement point, stepping on the gas will transmit power through the clutch and thus wear the clutch. This is why launching the car is hard on the clutch.

I'm no expert, so I hope this makes sense.

 

That's an interesting read. Thanks for the link. My favorite part:

 

With the clutch out in nuetral I don't think pressing the accelerator will be able to have any effect on the layshaft of the tranny if that's what you are saying...I'm trying to put this together in my head and found a good article:
http://auto.howstuffworks.com/transmission3.htm

The question I'm curious about is whether or not the clutch is constantly spinning while the car is in motion. I thought the clutch pedal only engages/disengages contact with the flywheel, which is always spinning at engine speed, thus the need to match revs with the tranny.

I do know that if you rev match (match the rev's of the engine to the speed of the transmission, which is being driven by the rear wheels, in the next lower gear), you cannot feel the engagement and it's smooth as silk. I've only been able to do it a few times while practicing heel-toe, but when you get it right it feels great - like when you drive a golf ball and nail the sweetspot of the club...you don't even feel it!

 

I think that just rev matching is enough. You can tell when you just pop it into gear that it's hard on everything. Even though that's what the sychros are for it's a smoother ride to rev match and I'd rather not have to replace synchros, .

 

Before you shift be sure and put some pressure on the stick in the direction of the gear you going to. For example if you are going to second from first. Pull down firmly as if going to second then when you hit the clutch it will shift very fast. Probably faster than you can let the clutch out if you are not ready. So just stab the clutch very quickly and don't worry about the gas and just leave it to the floor.

Oh yeah and don't worry it wont pop out of gear as long as you are on the gas.

 

That’s a really good way of hurting your tranny !

The synchro’s dogs are undercut (ie slanted) so that when power is transmitted thru it, it stays locked. Forcing it out like you suggest will wear the dogs and round them. Then you will get gears that pop out.

Also, the fork that will pull/push on the synchro might bend if you pull hard on it while still on the power.

More on these forks. They are basically a semi-circle that hug the synchro all the time. People who rest their hand on the shifter while driving will put some pressure on the fork. The fork will in turn rub on the synchro and basically grind them selves over time. You end up with a loose tranny with little feel.

It took me a while to figure out how a gearbox works. Something we must understand is that ALL gears are always engaged. Its the synchros that will lock the output shaft with one gear while all the others are “free wheeling” at each their respective speeds. Synchros are tiny… Be nice to them !

Double clutching is not necessary but can help. When jumping gears or engaging first or reverse.

 

Learn to rev match on downshifting. Don't power shift if you like your car. You don't need to double clutch on a Z and yes I learned to drive on a manual transmission that _had_ to be double clutched.

 

Personally I power shift when I race. That means don't take your foot off the gas and shift fast. It takes some practice...also not good for the clutch. But hey you've only raced once so give it a shot! BTW don't power shift into second it'll only slow you down.