I've searched but did not find an answer...so here goes!


What is the proper sequence for downshiftng to reduce jerking (for a car with synchros):

1st) clutch out, lower gear in, blip, release clutch (faster to execute, I think)

or

2nd) clutch out, blip, lower gear in, release clutch (slower, but more conventionnal)

My guess would be that the result is the same (no jerking, as input and output are matched), but that in the 1st scenario it would be that the synchros are doing more work.

any pros and cons to each?

Thanks

 

Try this:
Depress clutch, downshift gears, blip throttle and release clutch at the same time. (as described in scenario 1) is best and fastest in my opinion.
If you use scenario 2, you better have a very fast right hand as your throttle blip will have lost a lot of revs by the time you drop the lever into a lower gear.
If you can execute scenario 1 properly, you wont need the synchros, as the engine is doing all the work to allow a smooth gear change, so the synchros are not doing more work as you put it.

 

Thanks a lot. This is exactly the way I am doing it (scenario 1). It is just that most of the threads I could find about the subject on this forum mention scenario 2 as the way to do it. I tried, but was not able to do it properly, because of the fast falling revs. It helped, but was not as smooth (or fluid) as scenario 1 for me.

 

use method two when you're double clutching. i give it a second blip if the revs drop too low. method 1 when you're not.

 

I respectfully disagree. OK, you depress the clutch, then, without rev matching, you downshift? Even with the clutch still depressed, wouldn't the synchros have to work overtime to allow the transmission to be shifted to the lower gear???

I've always believed that you should depress the clutch, blip to rev match, downshift to the lower gear at a synchronous speed - hence little need for the synchros - and then ease the clutch pedal out.

Who's correct? Inquiring minds want to know....

WayneTN

 

So you guys are saying to blip with the clutch still pressed down? I don't see how that does anything helpful . I always double-clutch to downshift and it works just fine.

 

Scenario 1 as described by KY350 is the best way to do it. Double clutching is completely pointless w/ newer cars, as well as time consuming, but each to his own!

 

You can still rev-match without fully double-clutching and achieve some pretty smooth shifts. I do it all the time. Its a little harder on the clutch, but its still easier on the tranny...

 

I also found THIS LINK that confirms your conclusion.

WayneTN

 

great link and article...thanks for sharing.

so in conclusion, scenario 1 for regular driving with a street car equipped with synchros and scenario 2 for a race car or if you plan on ever driving one (with a real race tranny that is).

Happy to know I was doing it (and always have been) right. Took me so much practice to do it right and perfect. I would have hated to have to start again!

 

WayneTN - I couldn't access the link you posted so I don't know what was in it.
I believe that you can throw the lever into any gear at any speed, just don't let out the clutch before rev matching though. The syncros only work when you release the clutch. I am not a mechanic, so if I have told any porky pies, please correct me.

 

No, the synchros are put to work when you move the shifter into the lower gear's gate, before you pull out the clutch. That's the "whine down" sound you hear.

Here's a helpful and informative link.

 

Thanks for the link James. I think I've got it now.
When you downgear from 4 to 3 say, the syncho has done its think, before you let the clutch back out. Therefore, I should rev match before shifting to 3 to help the syncho do its job, then let the clutch out. This all happens in a short space of time, so that I don't lose revs.
Sorry about the earlier bumstear Scratchy / Wayne TN et al.

 

number one

 

I keep trying to think mmmmm, what do I do and I can't think of what I do. All I know is I drive the hell out of it..........lol

 

Here are the main steps that were outlined when downshifting through a curve and accelerating out (begin quote from article):

• Lift the right foot from the gas pedal and press the brake pedal
• Just before the braking is done, the left foot depresses the clutch pedal
• The right hand downshifts (the left is still on the steering wheel)
• The right foot is still applying, but easing up on the brake pressure, then rotates so the heel is above the corner of the gas pedal
• The right heel gives a quick push of the gas pedal to rev the engine quickly (the ball of the foot is still on the brake easing up even more)
• The left foot releases the clutch, the right foot rotate off the gas
• The right foot completes the braking
• The right foot slides over to the gas pedal to assume the normal position only to maintain some pressure to sustain the vehicle speed through the first part of the corner. Then accelerating out of the turn.

"The whole sequence above from the second bullet to the last takes less about half a second. This takes quite a bit of practice to get right. The whole idea is to transition between braking and accelerating with absolutely no delay, and with perfect smoothness. Done correctly, there should be no jerking of the car during the downshift and transition back to acceleration."

If you're really serious, you can buy special pedals that have wide extensions to help with the heel-toe execution.

hth,
WayneTN

 

1.

Like everyone has said, its such a quick thing, that it makes a hard thing a bit easier if you have it in the lower gear before blipping.

If the revs drop before you let the clutch out, it is totally pointless. It should be one complete rev, up to down. You are just about letting the clutch out while you blip, its a fraction before.

I am just getting the hang of it. I'd recommend at first to practice just braking and blipping while you downshift, don't worry about the timing part straight away. Get that heal toe action mastered first. Then comes the hard part, figuring out what speed/rpm to downshift at, how much to blip etc etc...but it's well worth the effort.