rev-matching question

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vw10
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rev-matching question

Post by vw10 » Wed Nov 12, 2014 10:58 am

when rev matching do i need to blip the throttle while moving the shifter knob to the lower gear or is it ok to blip it after i have selected the lower gear ??
Also i think we can hold the throttle instead of a blip as long as we don't keep the rpm too much over what they need to be (as it will be hard for the clutch to drag down the engine speed while we are feeding it with accelerator) so if at right rpms or lower it is perfectly fine right ?
Another one ... when up shifting is it important to use the throttle while at catch point or can we also do it before releasing the clutch ?

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RITmusic2k
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Re: rev-matching question

Post by RITmusic2k » Wed Nov 12, 2014 11:45 am

As long as we're not discussing a double-clutched shift, then the only thing we're trying to do is make sure the two sides of the engine/drivetrain interface are spinning as close to the same speed as possible at the time in which they make contact with each other. Meaning: "at the moment you're bringing the clutch pedal up to the friction point". The only difference between (1) blipping while moving the shift gate, (2) blipping after selecting the gear, (3) holding the revs steady, or even (4) blipping poorly and missing the mark, then taking your foot off the gas and waiting for the revs to fall, then trying again... is simply how much time you spend completing the process. Whatever you do before the spinning parts are touching each other doesn't matter. It won't matter until the parts are touching.

So in practice, you may take a little bit of time to get a feel for blipping your engine to the right RPMs. If you're only comfortable separating out each step at first, that's fine... just realize that you may have to adjust the size of your blip to account for the fact that the car is coasting down and changing road speed the whole time you've got the clutch disengaged. Eventually, though, you'll become more comfortable with overlapping the steps and blipping while moving the shifter, simply because it's faster to do so, and we naturally improve at tasks with repetitive practice.

Regarding your other questions about feeding throttle and being at the right RPMs or lower on downshifts, or using throttle before engaging on upshifts...

Again it doesn't matter how fast or slow things are turning before the clutch is engaged... just that engine speed and road speed are appropriately matched for the gear you're entering into at the point of re-engagement. Here's the other thing: overshooting your target RPMs and undershooting them are the same kind of error from a mechanical sense. Being 200RPMs too high and being 200RPMs too low will incur the same amount of wear on your clutch ("not much at all" in either case, by the way).

Holding throttle steady is actually a good way to do it; I generally disengage a gear and re-engage gear under partial throttle because it de-loads the whole drivetrain (force not feeding from the engine to the wheels, nor from the wheels to the engine). If you're rolling at a steady speed in gear, your engine will be turning at a certain speed... If sitting still and revving in neutral, there's a certain amount of throttle required to hold the engine at that same speed. This is the amount of throttle I try to apply when shifting out of gear - I'll know I've done it correctly if after disengaging the clutch my RPMs don't rise or fall. After I select my next gear (higher gear or lower gear depending on that I'm doing), then I have a new target engine speed based on how fast the engine will be spinning in that gear once the clutch is engaged... I raise or lower the engine speed accordingly, then let off the clutch.

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Re: rev-matching question

Post by AHTOXA » Wed Nov 12, 2014 3:06 pm

I think I end up blipping during the shifter movement. It's basically one motion of moving the shifter into desired gear and blipping.
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Re: rev-matching question

Post by daleadbull » Thu Nov 13, 2014 3:06 pm

As long as you have the clutch pedal down, you can blip before, during or after moving the shifter. It doesn't matter but blipping during is obviously the fastest.
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Ewilon1988
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Re: rev-matching question

Post by Ewilon1988 » Mon Mar 28, 2016 9:59 pm

I've been struggling with rev match downshifts. I've been driving my manual for about 3.5 months now. I think it's the blip part that I can't seem to get down and I get frustrated, so instead when I need to downshift(like taking a turn) I clutch out (while giving some gas). My smoothness doing that isn't great either. Any help with a beginner trying to rev match properly would be greatly appreciated.

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Re: rev-matching question

Post by Teamwork » Tue Mar 29, 2016 12:20 am

Ewilon1988 wrote:I've been struggling with rev match downshifts. I've been driving my manual for about 3.5 months now. I think it's the blip part that I can't seem to get down and I get frustrated, so instead when I need to downshift(like taking a turn) I clutch out (while giving some gas). My smoothness doing that isn't great either. Any help with a beginner trying to rev match properly would be greatly appreciated.
Hey Ewilon,

I can try and be of some assistance here. What is the specific scenario are we talking about when rev matching a down shift? I'm 7 months in now and I still sometimes flub my rev match when down shifting from a high to low gear when taking a 90 degree turn. I kind of get anxious when I see head lights behind me but I try and blip successfully regardless. Even if I miss by a little- usually letting out the clutch slowly smooths out everything. When it comes to rev matching a down shift chronologically on the open road though I seem to have that down a lot better (when not under pressure). So where do you usually feel like you're going wrong?

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Re: rev-matching question

Post by Ewilon1988 » Tue Mar 29, 2016 12:34 am

The times I try to blip I feel like I didn't get it close enough to where it needs to be so its a Bucky transition.

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Re: rev-matching question

Post by Ewilon1988 » Tue Mar 29, 2016 12:40 am

I also don't know the proper sequence as to rev matching. What's the best way to do it? Is it clutch in, downshift, blip, then release clutch? What's the proper order and is it done before or after the turn?

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Re: rev-matching question

Post by potownrob » Tue Mar 29, 2016 2:36 am

Ewilon1988 wrote:I also don't know the proper sequence as to rev matching. What's the best way to do it? Is it clutch in, downshift, blip, then release clutch? What's the proper order and is it done before or after the turn?
the sequence you mention is the correct sequence for a single-clutch downshift. you can also try double-clutch downshifts which just add a couple of extra steps but may help you get smoother downshifts. you can also let the clutch out a little slower after blipping the throttle, slowing through the engagement zone to ensure a smooth shift. ideally, you will want to downshift before the turn, but it is generally ok (though not as fun) to downshift after the turn too.
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Re: rev-matching question

Post by Ewilon1988 » Tue Mar 29, 2016 3:01 am

I'm going to practice what you said. i just hope I can get the "blip" part down. I'll definitely update after some practice runs

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Re: rev-matching question

Post by potownrob » Tue Mar 29, 2016 8:55 am

Ewilon1988 wrote:I'm going to practice what you said. i just hope I can get the "blip" part down. I'll definitely update after some practice runs
just remember it's more about sound and feel than numbers (as in amount of gas to add). It's more about trial and error and finding what feels and sounds right than watching the tachometer. Hope you catch my drift. Watch some YouTube downshift vids to get an idea of what it should sound like.

http://youtu.be/AGCXFDYXSXE
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Re: rev-matching question

Post by theholycow » Tue Mar 29, 2016 10:35 am

Ewilon1988 wrote:I also don't know the proper sequence as to rev matching. What's the best way to do it? Is it clutch in, downshift, blip, then release clutch? What's the proper order and is it done before or after the turn?
Your sequence sounds fine. Do it before the turn if you want to be in that gear during the turn; do it after the turn if you want to be in the previous gear during the turn or coast declutched. I generally do it when my speed and acceleration needs call for it, which could be before, during, or after the turn. (You might be saying "During? Isn't that verboten?"...yeah, if you're on a race track at the edge of losing control and you must shift harshly. On the road with other cars where you must always leave some safety margin in your traction and you prefer to shift smoothly anyway it's fine. A smooth shift won't upset traction, nor will a harsh one when there is traction to spare.)
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Teamwork
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Re: rev-matching question

Post by Teamwork » Tue Mar 29, 2016 12:48 pm

Ewilon1988 wrote:I also don't know the proper sequence as to rev matching. What's the best way to do it? Is it clutch in, downshift, blip, then release clutch? What's the proper order and is it done before or after the turn?
I usually follow that order of operations and I'll do it right before the turn. I usually wait to the last possible second because I'll need to typically catch 2nd gear for 90 degree angle ones (3rd sometimes if I'm carrying enough speed, safely) so I usually wait at the point where I'm carrying the least amount of speed leading up to the turn so I don't have to blip to a higher rpm to match revs. Depending on what amount of speed you take 90 degree angle turns "safely" you should see where your revs are at that speed in 2nd gear (if that's the gear you use). For my vehicle: I know if I'm taking caution and taking it slow at around 13-15 mph I will only need a short, quick stab in order to match the revs for 2nd gear. If I'm carrying a little more speed and want to get out of the hole faster at say 17-20 mph I will typically need to apply more pressure and sometimes I won't even stab the throttle (a quick on and off motion) but even apply gas to have the revs rise to the correct amount because I'm not great at matching a large amount of revs with a quick stab.

Hope this helps! But definitely understanding at least roughly where the rev's have to be at a certain gear/speed will aid this greatly.

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Re: rev-matching question

Post by Ewilon1988 » Tue Mar 29, 2016 3:14 pm

Very good video and the responses I received are appreciated! I'm going to keep practicing today. Is it okay to over or under rev by a little bit?

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Re: rev-matching question

Post by theholycow » Tue Mar 29, 2016 5:49 pm

Yes, it is ok. It's better to try to always improve your accuracy, of course. How far off are you talking about?

You can practice fine throttle control using some exercises that I describe in the meta-sig link in my sig.
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