Is pulse & bleed a valid technique?

[cfg83]

landspeed -

Originally Posted by landspeed

cfg83 : I am assuming the car is a manual.

Yes, a manual.

Double-declutching is just a way of reducing the stress on the synchromesh when changing gear.

Normally, if you are coasting, then input shaft will be spinning the speed of the engine (700RPM), whereas the output shaft will be spinning at a different speed.

When you go to put the car in gear (with the clutch down), the two shafts must be spinning at exactly the right speed, or the gear cogs will crunch badly. Synchromesh makes the input shaft spin at the correct speed as the output shaft, so that they can engage properly. If the synchro is worn, then the gears crunch (even with the clutch pressed down).

When changing from 1st-2nd, 2nd-3rd, 3rd-4th, 4th-5th, you can quickly change gear (synchro will help you, gearstick will have some resistance to
going in gear), or gently do it (gently resistance, when speeds match, gear will go in).

If changing down from 4th - 3rd... Or, from neutral - 5th, the synchromesh has to do a lot of work. Double-declutching can reduce the amount of work it has to do.

examples of double-declutching

(1) Car is in neutral, coasting along at 40mph
(2) If 5th gear would be 1500RPM, then rev engine to 1700RPM, *then*
press clutch in, change gear, and it will change a lot more easily.
....

Ok, I *almost* do something like this already, because I hit the accelerator right before I press the clutch to go from Neutral to 5th, but I am not consciously trying to match RPMS, it's just a smoother way to engage the gear. I am lucky in the sense that with my car, in 5th gear, the MPH and RPM needles "line up" at the same angle, so it is easy to "match the needles" to engage 5th.

CarloSW2