Sorry if we're redoing this, we'll come up with some new stuff to talk about soon

I'm going to have to get out and try these techniques to appreciate them so the descriptions are definitely helping.

 

[QUOTE=f1_fanz,Oct 4 2007, 08:49 AM]Sorry, I should have said 4-3-2, not 4-2 directly.

 

I don't have any problem with revisiting old topics. If we didn't revisit old topics we really wouldn't have very much to talk about.

 

[QUOTE=f1_fanz,Oct 4 2007, 09:49 AM]I've tried just braking and downshifting without dc and the car chirps and and lurches.

 

i'm pretty sure that on an upshift, the input shaft has to slow. for example, you're running to redline in 1st gear, the engine speed is matched to the input shaft when the clutch is engaged. you shift to 2nd because you're out of revs, so you want to be at a lower engine speed, which translates into a lower input shaft speed after the shift is complete and the engine & input shaft hooks up.

on a downshift, you get the opposite. your engine speed after the shift will be higher (thus blipping the throttle to rev match). double clutching lets you rev match the transmission input shaft to the desired engine speed which will both be higher than before the downshift.

Red_MX5, i also don't see how double clutching can transfer power from the input to the output shaft, unless we're talking about friction. so i guess the drivetrain (or more specifically transmission) loss is transferred to the output shaft? it couldn't be very much , because if you rev the car in neutral you won't get anywhere (but i guess static friction and inertia is much more to overcome than kinetic friction). i don't know, that's the only thing i can think of.

 

Great article that explains the basics of heel-and-toe & rev-matching:

http://www.edmunds.com/advice/youngdrivers...93/article.html


And basics of driving a manual tranny:

http://www.edmunds.com/advice/youngdrivers...20/article.html


I found this very true:

"Nowadays, driving a stick shift has become a lost art form as more and more people opt for the convenience and ease of an automatic. Unfortunate, considering how fun driving a manual transmission car is; you really get a sense of man-and-machine symbiosis when you master the manual transmission. And there's nothing like some good heel-toe action." -- Edmunds.com

 

^^ I don't even double clutch on the S2000 unless I'm shifting down to 1st gear. I just roll through each gear when I need to downshift ...

 

 

You don't even need to do that.

 

This has turned into a very interesting thread.

On an upshift, the engine speed drops after the shift, so the transmission input shaft need to be slowed to match the new engine speed. Double clutching doesn't help because the transmission input side slows naturally and isn't fighting the synchro's attempts to slow it down. On a downshift, the engine speed will be higher after the shift, so the input shaft of the trans has to be accelerated to the higher speed, either by the synchros, or by engine speed and a double clutch.

The required action for a double clutch is the same as for a rev match. For an upshift you don't need to worry because things slow down naturally, but on a downshift it takes a substantial stab at the throttle to get the revs up to match engine speed to the lower gear ratio.

Does that make more sense?