Up shifting smoothly

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Vyse

Original Poster:

1,224 posts

123 months

Monday 21st July 2014
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Ever since I went from driving a manual a few years back to then driving an auto my driving technique has become a bit suspect. I will freely admit my gear up shifts aren't always perfect. But during the journey home today I purposely changed my technique to suit my current car (the old technique worked quite wheel during my first stint at driving a manual).

Old technique: Depress clutch to the floor while removing my foot off the throttle completely in a smooth manner, change up the gear. Press the throttle gently while bringing the clutch up to the bite point. At this point my right foot stays in the same position and the clutch gets released completely. Within this technique my current car jerks quite a bit mostly going from 1st to 2nd.

New technique: Depress clutch to the floor while easing off the throttle slightly but never letting off completely, change up, then simultaneously let the clutch out while giving a little more throttle. Ive only started doing it today but it seems a bit smoother at least and the gears seem to slot in with more ease.


I'd like to ask what you guys do to make the changes going up smooth. Is my new technique right or wrong, will it damage the components more?

7db

6,058 posts

229 months

Monday 21st July 2014
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Oh lord we're going to need more popcorn.

For me, the upchange smoothness is determined by what you do with the throttle before you disengage the gear. Coming smoothly down to a neutral throttle so that there is no significant load through the drivetrain before you disengage the clutch and gear means that you are less likely to find you have a nodding dog as a passenger.

You then want the revs to fall off a little to match roadspeed in the new gear. That probably means off-throttle but -- pick your favourite method depending on what is happening next. You might go fully off throttle and then pick up again to the right speed (helpful if you are pressing on). You might come down a little and hold at what you think it the right level (better if you are easing into a cruise). I've experimented with a blip as a trigger action. A lot will depend on flywheel weight in the car and how quickly the revs change.

While that is happening you're engaging gear according to the natural slowing of the layshaft. In it pops as the gearbox spins down to road speed in the taller gear. And then you've got the throttle in the right place, up comes the clutch.

There are four actions -- clutch out gear out gear in clutch in -- and your goal is to not have your passenger feel any of them.

Vyse

Original Poster:

1,224 posts

123 months

Monday 21st July 2014
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If you let the revs drop too low when going up the gears will the not bog down and jerk when you reapply throttle?

VinceFox

20,566 posts

171 months

Monday 21st July 2014
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JUST CHANGE GEAR.

R_U_LOCAL

2,676 posts

207 months

Tuesday 22nd July 2014
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A few years ago Reg said:
The most important aspect of changing up correctly is what you do with the accelerator pedal. A lot of drivers will press the clutch and completely release the accelerator pedal whilst they change gear. They will then release the clutch prior to re-applying the accelerator. This technique will usually result in the car jerking forward when the clutch is released because the engine speed doesn't match the road speed for that gear. This jerk is more pronounced in lower gears than it is in higher gears.

The way to avoid this jerk is to release pressure on the accelerator before and during the gearchange, but not to release it completely. I'll talk you through it.

Lets assume we're about to change up from 2nd to 3rd in an average car, at about 40MPH. In this imaginary average car, the engine will be doing 5000RPM at 40MPH in 2nd gear, and 3000RPM at the same speed in 3rd.

Before you start to change gear, ease off the accelerator slightly so the rate of acceleration slows. Then press the clutch and change gear as described previously. Whilst you're changing gear, ease the accelerator back until the revs have dropped from 5000 to 3000, and then hold the revs there whilst you release the clutch. Once you've released it, squeeze the accelerator, and continue accelerating. Allowing the revs to drop correctly will remove that jerkiness from the up-change, and you'll notice the difference immediately.
From "Zen and the art of changing gear"...

www.pistonheads.com/gassing/topic.asp?h=0&t=36...

TheInsanity1234

740 posts

118 months

Tuesday 22nd July 2014
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Good to know that Reg feels the need to properly advertise his post by posting it 3 times! hehe

R_U_LOCAL

2,676 posts

207 months

Tuesday 22nd July 2014
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Don't know what happened there.

Nothing to see here. Move along now.

7db

6,058 posts

229 months

Tuesday 22nd July 2014
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Vyse said:
If you let the revs drop too low when going up the gears will the not bog down and jerk when you reapply throttle?
Yes. Don't let them drop too low.

All of the car's motion should be controlled by your sensitive right foot, not your clod-hopping left. The gentle feathering off to neutral prior to the disengagement of the clutch. The matching of revs to engine speed before the reengagement. These are right-foot activities.

Also - faster is usually better. A slow up-change requires accuracy which is lovely to see demonstrated but it is a bit harder to do.

jaf01uk

1,943 posts

195 months

Wednesday 23rd July 2014
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As explained previously changing gear from acceleration will always result in "noddy dogs" in passengers, the best way as described is to ease off the gas prior to changing gear so the car is just maintaining speed on a partial throttle, this is when you stick the clutch in but the important part (and counter intuitive bit) is to keep the gas pedal exactly where it is, once explained to me as "if you take your foot off you cut off the fuel supply to the engine thus when you go back on the gas you get a rush off fuel back in and that's what causes the jerk" By keeping your foot on the gas pedal at what will effectively be a "fast idle" you keep the fuel flowing and the rush of fuel back in is not noticeable. As also mentioned changing up the gears too quickly can "beat" the revs going into the next gear and result in the clutch coming up while the revs are too high for the next gear giving a surge as the clutch is released... happy motoring
Gary

Vyse

Original Poster:

1,224 posts

123 months

Wednesday 23rd July 2014
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That does make a lot of sense. I only experienced jerkiness from 1st to 2nd and sometimes 2nd to 3rd. I guess its because the torque difference is the largest at the lower gears right?

jaf01uk said:
As explained previously changing gear from acceleration will always result in "noddy dogs" in passengers, the best way as described is to ease off the gas prior to changing gear so the car is just maintaining speed on a partial throttle, this is when you stick the clutch in but the important part (and counter intuitive bit) is to keep the gas pedal exactly where it is, once explained to me as "if you take your foot off you cut off the fuel supply to the engine thus when you go back on the gas you get a rush off fuel back in and that's what causes the jerk" By keeping your foot on the gas pedal at what will effectively be a "fast idle" you keep the fuel flowing and the rush of fuel back in is not noticeable. As also mentioned changing up the gears too quickly can "beat" the revs going into the next gear and result in the clutch coming up while the revs are too high for the next gear giving a surge as the clutch is released... happy motoring
Gary

jaf01uk

1,943 posts

195 months

Thursday 24th July 2014
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Vyse said:
That does make a lot of sense. I only experienced jerkiness from 1st to 2nd and sometimes 2nd to 3rd. I guess its because the torque difference is the largest at the lower gears right?
Yeah the difference is more noticeable 1st to 2nd, once you get used to easing off the acceleration prior to changing it doesn't take long to ease back, clutch in, clutch out and back on the gas and will be silky smooth...

Tiggsy

10,261 posts

251 months

Thursday 24th July 2014
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VinceFox said:
JUST CHANGE GEAR.
thank god. thought i was on my own!

davepoth

29,395 posts

198 months

Thursday 24th July 2014
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Timing is the key - getting the shift just right so that you are engaging the clutch just as the revs have fallen to where they should be for the next gear. You shouldn't need to slip the clutch under throttle at all.


R_U_LOCAL

2,676 posts

207 months

Friday 25th July 2014
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Tiggsy said:
VinceFox said:
JUST CHANGE GEAR.
thank god. thought i was on my own!
There is nothing wrong with revisiting the simple actions that we normally carry out without any conscious thought. Like every aspect of driving, there are poor, rough, badly timed, jerky gearchanges and there are smooth, controlled, well timed and mechanically sympathetic gearchanges.

If you're a driving god and every one of your gearchanges is silky smooth and perfectly timed, then there are plenty of other threads for you on this forum.

Knocking someone who has asked a perfectly valid question with the intention of improving their skills makes you come across like a certain Sniff Petrol character.

http://sniffpetrol.com/2014/06/12/yet-more-ask-a-t...

MagneticMeerkat

1,763 posts

204 months

Friday 1st August 2014
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Something to add, possibly, when it comes to the all important first to second gear shift is that it's more difficult than the others.

The old Roadcraft manual used to teach first gear should only be used for getting the car rolling, overcoming the inertia. Then an immediate shift to second was required at the lowest possible speed prior to any acceleration.

Now I'm sure that was fabulous in a straight six Van Den Plas or whatever but times have changed. Modern engines are much revvier but lack the old-school motor's ability to chug - by which I mean generate reasonable torque from almost idling speed. Most of the old three speed cars will accelerate from about 1 mph in second gear; a modern car won't.

So where does this leave the modern world? I guess applying such a technique in a newish Euro Shopper hatchback isn't going to work. Changing first to second at the lowest possible speed isn't going to be smooth; simply because doing so will overload the engine briefly. Just think, the engine isn't at a stage on the rev counter where it's capable of doing much work so gets bogged down. Effectively you take the car out of the pulling away phase then put it straight back there - the engine, owing to the increased torque demands of second gear, has to work harder. Some drivers smooth this out by revving it and introducing a little clutch slip during the upshift. But one really ends up pulling away twice, if that makes sense.

Best to speed up a little more, say 10-15 mph in first gear and then shift. Better for the car, and the passengers. At that speed it becomes a straight gearshift, rather than a compound shift and move off!