Accelerating before clutch fully up
Discussion
Since changing car I have noticed if I shift into 3rd gear for example then lift the clutch up fully ( even slowly ) before accelerating I get a slight jolty movement.
The only way I can counter-act this is by accelerating just before the clutch is fully up, so say about 85% of the way up
Is this bad practice or not ?
I notice some slight vibration in my clutch pedal but that may have always been like that. ( Car has done 22,000 miles )
Thanks
The only way I can counter-act this is by accelerating just before the clutch is fully up, so say about 85% of the way up
Is this bad practice or not ?
I notice some slight vibration in my clutch pedal but that may have always been like that. ( Car has done 22,000 miles )
Thanks
Edited by MakaveliX on Saturday 12th November 14:24
Well yeah you need to match the engine speed to the shaft speed so that when they're mated, it doesn't jolt. Maybe your new car has more rev drop (less inertia or its held less during the shift) so you need to counter that.
It's not bad for the system to match. If anything it's better (to an extent you're not burning the clutch).
It's not bad for the system to match. If anything it's better (to an extent you're not burning the clutch).
The clutch shouldn't be let out on a closed throttle whilst changing up so, assuming that's what the OP is talking about, nothing is being done wrong. The sequence, generally, is: clutch in, let off throttle, change gear, gently depress accelerator and let clutch out. The reason for depressing the accelerator is to counter the rapid drop in engine revolutions brought about by putting the clutch in and closing the throttle at the same time.
What one wants to do, ideally, is re-engage the clutch with the engine turning at the right number of revolutions for road speed and new gear. If that isn't done, there will be a noticeable shock to the driveline as the revs are raised by the clutch re-engagement. The transition from deceleration to acceleration will also be felt more keenly.
What one wants to do, ideally, is re-engage the clutch with the engine turning at the right number of revolutions for road speed and new gear. If that isn't done, there will be a noticeable shock to the driveline as the revs are raised by the clutch re-engagement. The transition from deceleration to acceleration will also be felt more keenly.
Accelerating before the clutch is fully engaged will cause premature wear = bad
When changing up you need to blip the gas so the revs are close to wear they will be when the clutch comes up, eg
Eg 4th at 50mph is say 3500 rpm
3rd at 50 mph is sat 4500 rpm
Changing 4 to 3 at 50 blip the gas hard enough eg to 4800/rpm so by the time the clutch comes up the revs are falling to about 4500
Changing up eg 3 to 4 - either time it so the clutch is coming up by the time the revs get to 3500 or maintain a bit of gas so they don’t fall too low. Some engines spin down quickly, others take longer so exactly what you do depends on the car - also depends on where you’re changing from - to
Eg 3rd to 5th , or 3rd to 6th the revs have much further to fall, so timing is all that is needed.
When changing up you need to blip the gas so the revs are close to wear they will be when the clutch comes up, eg
Eg 4th at 50mph is say 3500 rpm
3rd at 50 mph is sat 4500 rpm
Changing 4 to 3 at 50 blip the gas hard enough eg to 4800/rpm so by the time the clutch comes up the revs are falling to about 4500
Changing up eg 3 to 4 - either time it so the clutch is coming up by the time the revs get to 3500 or maintain a bit of gas so they don’t fall too low. Some engines spin down quickly, others take longer so exactly what you do depends on the car - also depends on where you’re changing from - to
Eg 3rd to 5th , or 3rd to 6th the revs have much further to fall, so timing is all that is needed.
When changing up you will be blending the clutch out and the throttle in. They will overlap and this is necessary for a smooth ‘take-up’ of drive.
However you do need to limit this overlap so that you’re not slipping the clutch for an excessively long time. Once used to the vehicle it should be literally just a second or less that you are still on the clutch after you have begun to open the throttle.
Functionally the a way this is done is that fractionally before you reach the clutch biting point in the higher gear you want to have a little bit of throttle on so that the engine doesn’t drop all the way down to idle.
It does take time to commit this to muscle memory in each vehicle you drive. The best tool you have at your disposal is your ears. Turn the radio off or crack a window if it helps you hear. You want to hear the revs coming down as you depress the clutch to initiate the gear change and then the revs climbing again as you blend the clutch out in the higher gear.
If you have a jolt you are probably using too much throttle and/or you’re being too sharp and not progressive enough with the clutch .
Hard to explain this last bit really so it either helps or it doesn’t, but my driving instructor used to describe the action on the clutch pedal as ‘dragging the clutch up’- with the clutch, the job isn’t done until the pedal is all the way up. It needs to be a smooth and progressive action all the way.
However you do need to limit this overlap so that you’re not slipping the clutch for an excessively long time. Once used to the vehicle it should be literally just a second or less that you are still on the clutch after you have begun to open the throttle.
Functionally the a way this is done is that fractionally before you reach the clutch biting point in the higher gear you want to have a little bit of throttle on so that the engine doesn’t drop all the way down to idle.
It does take time to commit this to muscle memory in each vehicle you drive. The best tool you have at your disposal is your ears. Turn the radio off or crack a window if it helps you hear. You want to hear the revs coming down as you depress the clutch to initiate the gear change and then the revs climbing again as you blend the clutch out in the higher gear.
If you have a jolt you are probably using too much throttle and/or you’re being too sharp and not progressive enough with the clutch .
Hard to explain this last bit really so it either helps or it doesn’t, but my driving instructor used to describe the action on the clutch pedal as ‘dragging the clutch up’- with the clutch, the job isn’t done until the pedal is all the way up. It needs to be a smooth and progressive action all the way.
I assume this is shifting down? Others have already provided information on rev matching to prevent this. However, I want to add that it doesn't matter if you rev match or not, especially in your everyday car. The extra wear is negligible when you're just pondering around.
If you're driving a performance car with a ton of torque though, shifting down a gear while already at a high RPM could result in your rear wheels skipping along or straight up breaking traction all together. A good way in ditching your car on a bend if you try to shift down and accelerate out of the bend.
If you're driving a performance car with a ton of torque though, shifting down a gear while already at a high RPM could result in your rear wheels skipping along or straight up breaking traction all together. A good way in ditching your car on a bend if you try to shift down and accelerate out of the bend.
PGN said:
Sounds like it's caused by the clutch delay valve - hateful things!
Yeah basically if I shift up and then lift the clutch too quickly it will jolt a bit, me old Toyota never did this.As said the only way to counteract this is by lifting the clutch up really slowly, or accelerate just before the clutch is fully up ( is this what "rev-matching" is ) ?
The jolty movement you are experiencing when shifting gears and lifting the clutch up fully before accelerating is likely due to a problem with the clutch or transmission. The fact that you have to accelerate before the clutch is fully up to prevent this jolty movement is not a good practice and could be damaging your transmission over time.
The vibration you are noticing in the clutch pedal could also be a sign of a problem with the clutch, and it may be a good idea to have it checked out by a qualified mechanic. A worn or damaged clutch can cause poor performance and damage to the transmission.
It's recommended to get the car inspected by a professional mechanic as soon as possible to find the root cause of the issue and fix it, it could be a worn clutch, a problem with the transmission or a problem with the engine mounts. Avoiding this problem can prevent major damage and costly repairs.
The vibration you are noticing in the clutch pedal could also be a sign of a problem with the clutch, and it may be a good idea to have it checked out by a qualified mechanic. A worn or damaged clutch can cause poor performance and damage to the transmission.
It's recommended to get the car inspected by a professional mechanic as soon as possible to find the root cause of the issue and fix it, it could be a worn clutch, a problem with the transmission or a problem with the engine mounts. Avoiding this problem can prevent major damage and costly repairs.
DickyC said:
Practice changing gear without using the clutch. Pull it out of gear, match the revs in neutral, push into the next gear. It's not as hard as it sounds. And it helps with your concentration when driving too.
I do this from time to time - I wouldn't necessarily say "push into next gear" so much as offer the gear up... As you say, it's not as hard as it sounds.Starting place is to rev to higher RPM than required and gently hold it against the correct gear and it'll suck it in when the revs are right.
As you get better at it, it becomes easy to do.
I have a 2015 Mazda 3 SP25 GT - like most drive by wire modern cars the accelerator is not immediately responsive (as the MGB I once had!). Squeezing your toes in your shoe during a shift up works better than trying to push the gas pedal down. Same method works well to get a smooth drive in a Nissan Leaf with ePedal activated.
Brassblaster said:
DickyC said:
Practice changing gear without using the clutch. Pull it out of gear, match the revs in neutral, push into the next gear. It's not as hard as it sounds. And it helps with your concentration when driving too.
I do this from time to time - I wouldn't necessarily say "push into next gear" so much as offer the gear up... As you say, it's not as hard as it sounds.Starting place is to rev to higher RPM than required and gently hold it against the correct gear and it'll suck it in when the revs are right.
As you get better at it, it becomes easy to do.
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