Rev matching by numbers

[Slink_Pink]

To achieve optimum rev matching what is the best method - by numbers - i.e. knowing the correct revs for a given gear & speed (from memory or handbook) or by feel - i.e. (educated) guessing?

I need to improve mine as I've been tending to slip the clutch of recent but can't remember how I learned in the first place!

[TR4ffic]

IMO, I think you need to have a good appreciation initially of the change in revs required when going up or down a gear at a given speed - 500 or 750 revs, whatever it may be. That's the numbers bit... Then it's down to sensing - feel/touch and noise (I prefer to term in sensing rather than guessing!) plus lots of practice.

If your rev matching used to be OK but you've (temporarily) lost the knack, can I suggest that you go back to basics a bit - perhaps slow things down a bit or give yourself a bit more time - perhaps the time you used to give yourself but you have subconsciously 'speeded up' which is causing problems with the rev matching. Other than that, specifically go out when it's quiet and practice, practice, practice. When my son had just passed his test, I took him out on a nice, flat, empty stretch of road (we used a bit of the A5 near us - no bends to worry about either!) and we just practiced going up and down the 'box (3 > 4 > 5 > 4 >3) with no change in speed... Also, perhaps you are overthinking it a bit because you think you have an issue - it should be almost sub-conscious...

I don't want this to come across as patronising - hopefully it doesn't. If it does - apologies.

[7db]

I go by ear. There's an "interval" between gears in most cars. You can learn it fairly quickly in the opening phase of your drive -- do a dozen unnecessary change to learn the notes. I never look at the rev counter.

Feel is important too: you get a bit of feel from the first part of the change as you move the gear lever across that tells you if you're about to fluff the next bit.

It's hard to catch a falling knife so give yourself a chance and give your blip the same shape as the road speed change: Hard blips are good for slowing downchanges esp HnT. Sustain changes are better for wafty momentum-laden fixed speed changes.

Fear that you might be about to drag the clutch? Feel for it as you slowly release and compensate with the throttle if you find that you are off.

Hard blips sound better. Faster gear changes are easier.

[Mr Cholmondeley-Warner]

Knowing all the correct revs for any given speed in any gear is next to impossible. The interval method works better, although it depends on the spacing of the ratios in your gearbox. The Boxster, for example, has very different intervals between the gears - 3rd to 4th is a much bigger gap than 2nd to 3rd, and so on.

Ear works best if you have the aptitude. As 7db says, doing it faster is easier. Many people come to AD and learn to rev match better, and slow down gear changes, and thus actually make things harder for themselves by turning every gear change into a long drawn-out sustain, rather than a blip. When I start to struggle with "mechanical" gear changes, I go back to instinct and ear. Conversely, if I'm not getting it right by ear, sometimes concentrating on the proper intervals, watching the rev counter, and re-learning the engine notes, can help get back in tune. That's just me, though.

Likewise I do 7db's "feel and compensate" thing with the clutch and throttle, but I wish I didn't have to.

[jcochrane]

I don't look at the rev counter either. I squeeze the throttle a wee amount then blend for very minor adjustments if it feels I need to. I don't think about it, just do it subconciously.

If you feel you have "lost your touch" you may find practicing on a quiet flat road at a constant speed, as has been suggested, should help but in addition on the downshifts try a tiny squeeze of the throttle just ahead of dipping the clutch and keep the right foot steady throughout the rest of the change. Usually this helps to get the throttle, gear and clutch timing right. My quess is that you may be thinking too much about the change, in particular what to do with the throttle, and as a result are playing too much with throttle position and dithering with the clutch. Most of the time there only needs to be very subtle throttle movement, or none at all, from the "steady right foot" mentioned above to make neat changes.

Others have mentioned the sound of the engine may help but in some cars, like my own, it is very hard to hear the engine thus making it impossible to use this technique to help.

PS Sugestion above assumes a change down of one gear. A block change would, would of course, require more throttle. The above is an alternative to blipping the throttle and you may find it is worth a try.

[MrToad]

I have to say that having a louder car has done a lot to improve my gear changing accuracy.

The fact that you (and people in the next street) can hear even the slightest mis-match, clutch-slip or over-rev is quite a motivator to get it right.

[trashbat]

I mostly do it by sound and 'muscle memory'.

If I'm required to make a bigger leap, like downchanging two or more gears, I will use the rev counter.

It would be thoroughly daft to learn the RPM for all speeds in all gears, but you presumably know what revs you're at before the change and so can probably come up with an approximation for the new revs required.

[WhoseGeneration]

To achieve optimum rev matching what is the best method - by numbers - i.e. knowing the correct revs for a given gear & speed (from memory or handbook) or by feel - i.e. (educated) guessing?

I need to improve mine as I've been tending to slip the clutch of recent but can't remember how I learned in the first place!

Do you really mean "slip the clutch" or is it actually dragging the clutch?
Next question is what is the car and fuel type and whether a cable or DBW controlled throttle?

[waremark]

Any of timing, sound, foot position and rev counter can help. The rev counter helps to calibrate the other indicators - and can certainly tell you how accurate you were.

Rather than actually looking for a number on the rev counter, I often catch the movement of the needle in peripheral vision.

[fungus]

I never look at the rev counter and make my gear changes by ear. If only dropping one gear, I usually maintain light pressure on the throttle, but dropping two gears I usually blip or double de clutch.

[Slink_Pink]

Thanks all for the feedback. It's good to hear that others occasionally mess it up too! In more recent journeys it has been a little better so it's perhaps something I've made an issue out of by overthinking as some of you suggested. I still have room for improvement though so a little practise at some quiet point is a very good suggestion. I think that as it's a new-ish car I have just got a little less experience over the wide range of driving conditions and speed as it's mostly been used for motorway commuting.

I mostly do it by sound and 'muscle memory'.

...Most of the time there only needs to be very subtle throttle movement, or none at all, from the "steady right foot" mentioned above to make neat changes...

These ring particularly true when I reflect back so I'll try and be a little more trusting of my instincts too.

[WhoseGeneration]

From time to time I have a little "play" with gear changing. In a whatever limit that has little other traffic around, I'll try to keep at the limit whilst going up and down the applicable gears without any perceptible change of speed or that the change itself would be noticed by a passenger, apart from, perhaps, the sound of the engine related to its revs.

[Graham Wright]

I see the two benefits of rev matching as smooth gear transitions and reduced clutch wear.

However, It is now around 50 years since I had any problem with a clutch (and that was an internal link breakage in a Humber Super Snipe). How about other forum members?

Our current main car has 300,000 miles on the clock and nothing has been changed apart from a head gasket (due to incorrect coolant). Mind you, it is a Volvo!

I rev match by ear as I am an engineer and can see the sense. Consequently, my gear changes are smooth and there are no jolts.

There are no jolts either when my wife changes gear but she does not rev match. She achieves smoothness by clutch slipping and allowing the engine and transmission revs to match.

Please explain why this is unacceptable. Clutches are designed to slip - that is their main function at least when engaging the drive chain. (……and they are designed not to slip once engaged - before anyone comments!).

Stand by Fred!

[trashbat]

Slipping means increased clutch friction, friction means wear and wear ultimately equals replacement clutch.

Once driving with some degree of mechanical sympathy, whether it's meaningful in the typical ownership timeframe of a car is another question.

[Graham Wright]

Slipping means increased clutch friction, friction means wear and wear ultimately equals replacement clutch.

Happened to you?