Downshifting Query

[mark_mcd]

Quick question I hope...

When attempting to downshift without needing the brakes i.e. from 5th to 3rd should I be taking my foot off the throttle when dipping the clutch? Wondering if there are any bad effects to the transmission if you dip the clutch whilst still maintaining throttle position?

Thanks in advance.

[vonhosen]

Depends what type of gear change you want to do (ie sustained revs).

[p1esk]

vonhosen said:

Depends what type of gear change you want to do (ie sustained revs).

A degree of sustained throttle more like. The revs can't be sustained; they obviously need to increase for a downchange.

The terminolgy used is sometimes imprecise, and it can be misleading to somebody who is new to these things and trying to understand what it all means.

Best wishes all,
Dave.

[Neil.D]

Rev matching (for the lower gear) is preferable for smoothness, vehicle control and stability. HTH.

[The Black Flash]

mark_mcd said:

Quick question I hope...

Questions about gearchanging are never quick in here
I can't see how you'd do any harm by not lifting off the throttle. But as everyone else says, you ideally want to match the revs for the lower gear.

[RobM77]

Personally I'd wait till the clutch is disengaged before applying throttle to rev match, otherwise you'll be dragging/slipping the clutch plates when they're pulled apart.

[BertBert]

mark_mcd said:

Quick question I hope...

When attempting to downshift without needing the brakes i.e. from 5th to 3rd should I be taking my foot off the throttle when dipping the clutch? Wondering if there are any bad effects to the transmission if you dip the clutch whilst still maintaining throttle position?

Thanks in advance.

I think it partly depends on what throttle position you had in the first place, ie what manoeuvre you are engaged in.

Eg closed throttle, reducing speed. You'd need to raise revs at some point in the gearchange to rev match.

Eg WoT accelerating in 5th, situation changes, your plan needs third...probably not sensible to depress the clutch with the throttle against the stops (slightly contrived example before anyone mentions it).

It also partly depends on your "strategy". Some people like the idea that if you are pootling in a gear with a modest throttle opening and you depress the clutch to change down, keeping the throttle in the same place, magically raises revs to the right revs for the lower gear. I don't like that approach and prefer to depress the clutch with the throttle closed.

Bert

[RobM77]

Out of interest, why would anyone sustain revs rather than blipping? Is it kinder to the engine's connected ancilaries (e.g. oil pump) or something? I just follow the standard technique when changing down of declutching, then blipping to just above the revs for the new gear as I engage the new gear, then letting the clutch pedal up again when the revs are falling past where they need to be. Really easy and I do it without even thinking.

[SamHH]

RobM77 said:

Out of interest, why would anyone sustain revs rather than blipping? Is it kinder to the engine's connected ancilaries (e.g. oil pump) or something? I just follow the standard technique when changing down of declutching, then blipping to just above the revs for the new gear as I engage the new gear, then letting the clutch pedal up again when the revs are falling past where they need to be. Really easy and I do it without even thinking.

I think it's easier to use sustained revs.

[1950trevorP]

RobM77 said:

I just follow the standard technique when changing down of declutching, then blipping to just above the revs for the new gear as I engage the new gear, then letting the clutch pedal up again when the revs are falling past where they need to be.

"standard" for whom?

[anonymous-user]

1950trevorP said:

RobM77 said:

I just follow the standard technique when changing down of declutching, then blipping to just above the revs for the new gear as I engage the new gear, then letting the clutch pedal up again when the revs are falling past where they need to be.

"standard" for whom?

I've never done it like that. Why drop the revs, then blip them (presumably beyond where they need to be) and 'catch' them on the way down? Seems a very contrived way of doing something that should be simple.

[ScoobyChris]

The two real options are the "blip and catch" or the "squeeze and sustain". The blip sounds better in most petrol cars but can upset some delicate folks who don't like "noise". The sustain requires more accurate use of the throttle to set the correct revs for the new gear before enagaging but gives you the choice as to whether you do a quick gear change or a slow one.

I'll use a mixture depending on mood.

Chris

[RobM77]

Symbolica said:

1950trevorP said:

RobM77 said:

I just follow the standard technique when changing down of declutching, then blipping to just above the revs for the new gear as I engage the new gear, then letting the clutch pedal up again when the revs are falling past where they need to be.

"standard" for whom?

I've never done it like that. Why drop the revs, then blip them (presumably beyond where they need to be) and 'catch' them on the way down? Seems a very contrived way of doing something that should be simple.

I can see your point, but to me it seems odd to learn two techniques (blipping and sustained) when one will do. Everyone needs blipping, because 90% of the time when you're changing down you're on zero throttle or braking, so what I've always done is just used that technique when changing down from a steady throttle (preparing to overtake is the only situation I can think of right now). I've always been aware of the existence of sustained rev downchanges, but just thought of them as a rather quirky and eccentric way of changing gear. In fact I think I've only tried it a couple of times. I'll have a go tomorrow

[1950trevorP]

I was taught (some would say "brainwashed") the "beginners" rev-matching method.
That is:- http://artofgearchanging.blogspot.com/

"we" then progessed to other less smooth methods when, erm, progress became the primary requirement.

There have been umpteen versions on PH of "my way is best".

In all truth, it does not matter.

Anything that is Safe. Preferably also Legal and smooth and considerate.

The "beginners" rev-matching as described is normally taught to those learning The System.
After that - choose whichever of the racing/ballerina techniques you fancy.

[SamHH]

RobM77 said:

I can see your point, but to me it seems odd to learn two techniques (blipping and sustained) when one will do. Everyone needs blipping, because 90% of the time when you're changing down you're on zero throttle or braking, so what I've always done is just used that technique when changing down from a steady throttle (preparing to overtake is the only situation I can think of right now). I've always been aware of the existence of sustained rev downchanges, but just thought of them as a rather quirky and eccentric way of changing gear. In fact I think I've only tried it a couple of times. I'll have a go tomorrow

Why would you ever "need" to use the blip method to rev match? Why can't you just get the revs to what you need them to be, then engage the gear?

[RobM77]

SamHH said:

RobM77 said:

I can see your point, but to me it seems odd to learn two techniques (blipping and sustained) when one will do. Everyone needs blipping, because 90% of the time when you're changing down you're on zero throttle or braking, so what I've always done is just used that technique when changing down from a steady throttle (preparing to overtake is the only situation I can think of right now). I've always been aware of the existence of sustained rev downchanges, but just thought of them as a rather quirky and eccentric way of changing gear. In fact I think I've only tried it a couple of times. I'll have a go tomorrow

Why would you ever "need" to use the blip method to rev match? Why can't you just get the revs to what you need them to be, then engage the gear?

I'm not sure I follow you.

Let's say you've backed off for a bend up ahead and you want to change to a lower gear more suitable to your new road speed (say, from 2k in 4th to 3k in 3rd). What I would do would be to declutch, get the revs up to just above those of the new gear (by prodding the throttle) as I select the new gear, and the let the clutch up. By timing it right (i.e. declutch at 3k) you don't even feel it. How else would this be done?

I must have mis-understood the sustained rev method, because to me it sounds really difficult. Blipping the throttle to 5k and lifting the clutch at a set number of revs for example is really easy. I was doing this as a child when I could only just reach the pedals! Raising the revs and holding them there is much much harder. It's what I have to do for noise tests each time I go on track and whilst I can do it, holding a set number of revs focuses the mind somewhat. I wouldn't want to have to do it whilst driving. Surely I've mis-understood this method of changing gear (I'm barely aware of its existence to be honest, so bear with me!)?

[SamHH]

RobM77 said:

Let's say you've backed off for a bend up ahead and you want to change to a lower gear more suitable to your new road speed (say, from 2k in 4th to 3k in 3rd). What I would do would be to declutch, get the revs up to just above those of the new gear (by prodding the throttle) as I select the new gear, and the let the clutch up. By timing it right (i.e. declutch at 3k) you don't even feel it. How else would this be done?

I must have mis-understood the sustained rev method, because to me it sounds really difficult. Blipping the throttle to 5k and lifting the clutch at a set number of revs for example is really easy. I was doing this as a child when I could only just reach the pedals! Raising the revs and holding them there is much much harder. It's what I have to do for noise tests each time I go on track and whilst I can do it, holding a set number of revs focuses the mind somewhat. I wouldn't want to have to do it whilst driving. Surely I've mis-understood this method of changing gear (I'm barely aware of its existence to be honest, so bear with me!)?

No, you've not misunderstood it. The technique I'm referring to is where you press the throttle pedal until the engine is at the correct revs, then release the clutch pedal. You could hold the revs at the correct level for as long as you want.

I find this much easier than prodding the throttle then trying to predict exactly how quickly the revs will fall from, say, 5000 rpm as in your example, and timing the release of the clutch pedal to coincide with this.

Also — and I know this shouldn't really matter — I'd feel a bit of a prat revving to 5000 rpm when I only need 3000.

[vonhosen]

p1esk said:

vonhosen said:

Depends what type of gear change you want to do (ie sustained revs).

A degree of sustained throttle more like. The revs can't be sustained; they obviously need to increase for a downchange.

The terminolgy used is sometimes imprecise, and it can be misleading to somebody who is new to these things and trying to understand what it all means.

Best wishes all,
Dave.

You wouldn't be likely to be using sustained throttle for the 5th to 3rd. You would be dipping the clutch & depressing the throttle further until it got to the required revs before steady foot to sustain those revs, then letting the clutch back up.

[RobM77]

SamHH said:

RobM77 said:

Let's say you've backed off for a bend up ahead and you want to change to a lower gear more suitable to your new road speed (say, from 2k in 4th to 3k in 3rd). What I would do would be to declutch, get the revs up to just above those of the new gear (by prodding the throttle) as I select the new gear, and the let the clutch up. By timing it right (i.e. declutch at 3k) you don't even feel it. How else would this be done?

I must have mis-understood the sustained rev method, because to me it sounds really difficult. Blipping the throttle to 5k and lifting the clutch at a set number of revs for example is really easy. I was doing this as a child when I could only just reach the pedals! Raising the revs and holding them there is much much harder. It's what I have to do for noise tests each time I go on track and whilst I can do it, holding a set number of revs focuses the mind somewhat. I wouldn't want to have to do it whilst driving. Surely I've mis-understood this method of changing gear (I'm barely aware of its existence to be honest, so bear with me!)?

No, you've not misunderstood it. The technique I'm referring to is where you press the throttle pedal until the engine is at the correct revs, then release the clutch pedal. You could hold the revs at the correct level for as long as you want.

I find this much easier than prodding the throttle then trying to predict exactly how quickly the revs will fall from, say, 5000 rpm as in your example, and timing the release of the clutch pedal to coincide with this.

Also — and I know this shouldn't really matter — I'd feel a bit of a prat revving to 5000 rpm when I only need 3000.

Thanks; I understand now. That's kind of like what I do to be honest. I change gear quite quickly and my road cars have reasonable flywheels, so I'm only really blipping about 200-300rpm over what I want. As far as I understand it, the difference between what I do and this sustained revs thing is that I wait until the clutch plates are seperated before spinning up the engine side; as it was explained above I imagined the driver seperating the clutch plates with load on them, which doesn't sound very mechanically sympathetic to me, easy to do, or portable between scenarios.

[p1esk]

vonhosen said:

p1esk said:

vonhosen said:

Depends what type of gear change you want to do (ie sustained revs).

A degree of sustained throttle more like. The revs can't be sustained; they obviously need to increase for a downchange.

The terminolgy used is sometimes imprecise, and it can be misleading to somebody who is new to these things and trying to understand what it all means.

Best wishes all,
Dave.

You wouldn't be likely to be using sustained throttle for the 5th to 3rd. You would be dipping the clutch & depressing the throttle further until it got to the required revs before steady foot to sustain those revs, then letting the clutch back up.

No, beg pardon and all that, but it doesn't matter whether you're changing from 5th to 4th, or 5th to 3rd. What matters is how much throttle you're using before you start the gearchange, and how much throttle is needed to raise the engine speed to the level required to suit the new (lower) gear.

For example, if you are climbing a moderately steep hill in 5th gear you'll have a fair amount of throttle opening, and if you maintain that amount of throttle the revs will go too high when you de-clutch, and this will be the case whether you are going for 4th or 3rd, and maybe even 2nd gear. In a situation like that you will need to reduce the throttle opening, but you need not go to a closed throttle position. You are maintaining (or sustaining) some throttle opening, but it will not be the same amount of throttle throughout the process.

Alternatively, you may be driving on a level road in 5th gear and wish to change to 4th or 3rd gear. In this case the existing throttle opening will be much less, and therefore the revs will not rise so quickly when the clutch is disengaged for the downward gearchange. In this case you may be able to maintain (or sustain ) the existing amount of throttle (or something very close to it), and if it works really nicely you should find that the revs rise gently to a level which matches the engine speed for the new lower gear. When you get that result you are entitled to feel you've made a nice sustained whateveritis gearchange.

Anyhow this is not a technique I make much use of, but I reckon that's how it works. Like most things it takes a good deal of practise, but it can give a very pleasing result when it is done well.

Best wishes all,
Dave.