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JFairman JFairman is offline
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Join Date: Jul 2006
Location: S. Florida
Posts: 7,274
Originally Posted by 911st View Post
The 'synchro' can do the job of the 'first blip' of the throttle when double clutching (engagement teeth speed to the gear speed).

The 'second blip' is to match the clutch disk to the flywheel so traction at the rear wheel is not impacted.
You don't blip the throttle twice while double clutching while shifting up or down so there is never a "second blip" unless you have a problem or screwed up the rev matching the first time and have to do it again while still in nuetral.

Helical or straight cut gearset teeth has nothing top do with it. All the gearsets are always engaged with each other all the time no matter how the teeth are cut but one of the two gears in each gearset is not locked down to the shaft it's on and is freewheeling on it's needle bearings until the synchro slider is moved over by the driver and engaged with the the gearsets selector teeth, locking it to the shaft and engaging that gear.

When double clutching, the first time you press down the clutch pedal is to shift out of gear into nuetral. Then while in neutral you let the clutch out very quickly and blip the throttle at the same time so the engine, clutch, and gearset rpms speed up to the same rpms or a tiny bit higher then they will be when the next gear you're going for is selected.
Then the cluctch is pressed in again and you shift out of nuetral into that gear and let the clutch out and go.

All that is done VERY quickly and the reason a competitive race car driver doesn't double clutch in a car with a synchromesh transmission is it takes a little more time and lap times will be slower because you're not on the gas as much.

The driver will still heel and toe so he matches the rpms while braking into a corner during downshifts but that is so there is no lurch when letting out the clutch in the gear selected at the limits of adhesion entering a corner and downshifting is as smooth as possible.
Old 07-28-2010, 11:41 AM
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