Question about rev matching

[lawnchair]

Greetings all. I have a couple questions about rev matching. A little about me: I've been driving manual transmissions for about three years; my first was a 2008 Mazda3, and right now I'm in Japan driving a 1999 Daihatsu Mira (one of the tiny 660cc engine buggers). My next car, when I return to the States in the fall, will be a Golf, probably the 2010 or 2011. While I do have experience driving the manual transmission, I have been confused about the proper way to treat one, and have found a lot of conflicting information, so I thought I would give a shot asking my specific questions here.

So my first question is about rev matching while slowing down (to a stop, to go around a curve, etc.). I have heard variously that it is completely unnecessary in modern cars because of synchronized gear boxes, that it can help relieve wear on the synchros, that it can help but can do unnecessary damage if not done perfectly, and that it is up to personal preference and will not significantly contribute to wear and tear on the transmission. What are your takes on this? I expect responses as varied as what I have outlined about, but we'll see.

My second question is about what kind of rev matching to do. Are double-clutching (clutch in, shift to neutral, clutch out, throttle blip, clutch in, shift down, clutch out) and single-clutching (clutch in, shift to neutral, throttle blip, shift down, clutch out as I understand it, never done this one) different means to the same end, or do they do different things? The reading I have done has left me uncertain on this point.

My third question is about shifting down to accelerate, either to pass somebody or because you slowed down and now have to downshift in order to accelerate again. In this case, would it be appropriate to rev match?

I've tried to be clear with what I'm asking. If there is anything in my questions that is unclear please let me know. I would appreciate any help or info or personal opinion you can provide. Thank you.

 

[Deaks2]

Q1: For smoothness and less drivetrain shock and clutch wear, always rev-match. Synchromesh alleviates the need to double-clutch, but you still need to rev-match.

Q2: Rev-match = clutch in, blip the throttle while downshifting, clutch out

Q3: Yes, rev-match for the same reasons as Q1.

In low-traction situations, such as rain or snow, not rev-matching could lead to a loss of traction and a subsequent loss of control of the car.

 

[tplociniak]

I have a question in regards to this as well, when trying to rev match a down shift, I know the purpose is to match the rpms to the gear you will be shifting to, but if you were to be off, would it be better to be high (reved above selected gears rpms) or low (not enough revs to match selected gears rpms)?

 

[BS2H]

Downshifting all the time during a drive around town would be completely exhausting. Usually I go around town in 4th gear. When coming to a stop I'll keep it in gear and let the 4th gear engine break until about 15mph (the speed that the engine will start to shutter) then I'll let in the clutch and cruise to a stop. Doing this saves brakes, and clutch from too much shifting.

On the highway? Going through EZ-Pass for example, from 60mph, let in clutch -> neutral cruise to about 15 mph, go through the toll, then blip the throttle, put it in 3rd and keep going
I find that if you try to downshift on highway speeds, you have to keep rev matching gears and by the time you downshift from 6th to 4th you are at the toll anyway...(then you have to find change for the toll) Seems more distracting.

The only time I downshift is going around corners when the rpm's are going to be too low for that gear. For example driving in 4th...going around a corner at 12 mph, I'll downshift into 3rd when the rpms are around 1k. Synco's don't need to manage much, maybe a 100-200 rpm change.

Hope this helps.

 

[Erwan1]

Downshifting all the time during a drive around town would be completely exhausting. Usually I go around town in 4th gear. When coming to a stop I'll keep it in gear and let the 4th gear engine break until about 15mph (the speed that the engine will start to shutter) then I'll let in the clutch and cruise to a stop. Doing this saves brakes, and clutch from too much shifting.

On the highway? Going through EZ-Pass for example, from 60mph, let in clutch -> neutral cruise to about 15 mph, go through the toll, then blip the throttle, put it in 3rd and keep going
I find that if you try to downshift on highway speeds, you have to keep rev matching gears and by the time you downshift from 6th to 4th you are at the toll anyway...(then you have to find change for the toll) Seems more distracting.

The only time I downshift is going around corners when the rpm's are going to be too low for that gear. For example driving in 4th...going around a corner at 12 mph, I'll downshift into 3rd when the rpms are around 1k. Synco's don't need to manage much, maybe a 100-200 rpm change.

Hope this helps.

Seems to be that you should have purchased an automatic....

Being in the right gear is very important to your safety and the safety of people around you when driving a manual. Being able to accelerate (and quickly) by just pressing the gas and not having to figure out what gear you should be in or run into the possibility of stalling is important.

Anyway, back on topic. Once you get used to rev-matching it become second nature to driving a manual as you know it. Start doing it and soon enough you won't realize it, to make it quicker you can heel-toe. Takes more practice but again once you get it its easy and will become just part of regular manual transmission driving.

It is best practice to rev-match and as stated previously will not damage your car!

 

[RacingManiac]

I think there is a difference in driving fast/spiritedly and just cruising around town at a much more relaxed pace....you don't need to heel-toe your way down to every light....

 

[Erwan1]

I think there is a difference in driving fast/spiritedly and just cruising around town at a much more relaxed pace....you don't need to heel-toe your way down to every light....

You don't need to but as I said if you start doing it you won't even notice you are after a while and its much smoother and quicker than not.

 

[Deaks2]

I agree with Erwan about being in gear as much as possible. In the UK, if you put the car to neutral while at a stop light during your driving test you immediately fail. You need to keep the car in 1st with the clutch in.

I have a question in regards to this as well, when trying to rev match a down shift, I know the purpose is to match the rpms to the gear you will be shifting to, but if you were to be off, would it be better to be high (reved above selected gears rpms) or low (not enough revs to match selected gears rpms)?

Over time you will rev match properly, however, if i were to choose higher or lower when downshifting, I'd pick higher. Higher jsut means a little more clutch wear, lower gives the car a terrible jerk that can break traction. In Canada, in the winter, that can be a very bad thing...

 

[Bruno2000]

You brain need to figure out the best gear relative to your speed to play with your nimble car easier and safer.

-Playing into the high rev (3.5k+) when accelering will give u better power when need.
-Rev-matching is essencial between each gear switch when downshifting, period. Still important in up-shifting but the process is faster and easier.
-Playing with your gears to downshift to brake the car work just a little, u downshift to get rdy to re-accelerate more that brake. U have brakes to brake Mix it with downshift is a good idea.

Never forget that any gear downshifted will direct to a +/- 1k rev

exemple;

4th gears at 3k downshift = 4k on the 3th gear. Higher is the number, higher it will brake, more crucial u need to rev-match to not break your clutch/disc transmission.
Higher rev you downshift, higher damageable it is for the engine.

U have to always be rdy to fully press the clutch and recover it with gentle to not hurt the engine.


Im using manual tranmission for a while now, im not even think about all of this when I drive now, its automatic in my brain.

Practice and it will become part of you.

 

[Bruno2000]

http://www.drivingfast.net/car-control/rev-matching.htm

Here a good link to understand the downshifting with rev-match and heel-toe technic.

Rev-match will help to not get jerky feeling between each gear change and get smooth as butter feeling when succesfully executed.

Rev-match working with the friction point and adding some little power between each change gear. It can be use to up-shift too when the acceleration is slow and u wont any jerks/stale feeling.

Good luck

 

[ghostwind]

You don't need to but as I said if you start doing it you won't even notice you are after a while and its much smoother and quicker than not.

Rev matching, absolutely, but heel-toe is pretty silly and unnecessary on the street. It's important on the track where you are braking very hard and downshifting/rev-matching at the same time, but on the street you never brake that hard. No need, and in fact you may end up doing it badly, which in turn will hurt you on track. Why? Because unless you are deep/hard on the brake pedal (which again is not on the street, unless you are driving like a hooligan, and not even then), you will learn to heel-toe with the brake pedal a bit higher than you'd do it on track. This in time will create an incorrect technique when you do get on the track r.e. pedal positions. I've seen it too many times to count. I know people think it's kind of cool and racy for the street, but really no need IMHO.

 

[Erwan1]

Rev matching, absolutely, but heel-toe is pretty silly and unnecessary on the street. It's important on the track where you are braking very hard and downshifting/rev-matching at the same time, but on the street you never brake that hard. No need, and in fact you may end up doing it badly, which in turn will hurt you on track. Why? Because unless you are deep/hard on the brake pedal (which again is not on the street, unless you are driving like a hooligan, and not even then), you will learn to heel-toe with the brake pedal a bit higher than you'd do it on track. This in time will create an incorrect technique when you do get on the track r.e. pedal positions. I've seen it too many times to count. I know people think it's kind of cool and racy for the street, but really no need IMHO.

Fair enough, I could see how it may affect technique. I guess it hasn't for me yet, and practicing on the street seems to have helped more than not.

 

[ghostwind]

Fair enough, I could see how it may affect technique. I guess it hasn't for me yet, and practicing on the street seems to have helped more than not.

I still think the best place to practice it is on the track. Also on the street, as a technique, I don't see why one would do it (unless it's just for fun - which is OK I suppose). While on the other hand, rev-matching should absolutely be done all the time. On track, both need to be done all the time. That's the difference.

Another thing is obviously car to car pedal variation and brake assist. Some cars like the GTI have a LOT of brake assist - too much so for me anyways, very mushy. At first I thought there might be some air in the lines, so I flushed the fluid which helped a tiny bit, but still too much assist. So the pedal goes down far even under "gentler" braking. On my 911, this is not the case. So yeah, there's this factor as well.

Don't know. To each his own. But yeah, I have seen over the years people coming to the track with incorrect heel-toe technique that they learned on the street. You really need some clear roads with hard braking zones and no cops!

BTW, Erwan - what's your track set-up? Stock rotors/calipers?

 

[Bruno2000]

Heel-toe technic is reserved for tracks.

Like u guys said, useless in streets.

On the track, use the brakes to slow down and the engine to accelerate. Engine braking is not as efficient, and will not slow you down quickly enough for track use. If you have time to use engine braking, you're not going as quickly as you could

 

[Erwan1]

Heel-toe technic is reserved for tracks.

Like u guys said, useless in streets.

On the track, use the brakes to slow down and the engine to accelerate. Engine braking is not as efficient, and will not slow you down quickly enough for track use. If you have time to use engine braking, you're not going as quickly as you could

Well I disagree, heel-toe isn't "reserved" for the track. You can practice the basics of it on the street, I do and I feel it helps me on the track.