rev matching

[gundamz2001]

Hi all,

I have a question about rev matching during down shifting. Do I tap on the gas while I'm shifting (like when the stick is around the neutral position), or when the stick is on the desired gear.

Thanks for any input !

[AHTOXA]

Any time between clutch disengagement from the current gear to between clutch engagement into new gear. The motion of switching to new gear and rev matching is rather fluid. The throttle blip starts somewhere during the arm movement as you shift to a few gear.

[potownrob]

what tony said . keep in mind you need to be somewhat quick with the pedals to have the right amount of gas there when the clutch reengages. that's not to say you should necessarily be quick with adding gas and clutching while practicing, but rather that you might have some botched downshifts until you get the movements down. there are also at least 2 ways to downshift, single-clutched and double-clutched. Single-clutch downshifts are where you put the clutch in and move the stick directly to the lower gear and add gas somewhere in between when you clutch in and clutch out; for double-clutched downshifts you clutch in, move the stick to neutral, let out the clutch, add gas, move the stick to the lower gear and then let the clutch out. the second one sounds harder than it is but, once you get the movements down (and it becomes natural feeling), it's really not any harder (maybe more tiring though). that said, i usually stick to single-clutched shifts.

[gundamz2001]

thanks for the quick reply ! I am currently doing adding gas after stick in the desired gear position, while still clutch in. Besides this is slower than adding gas while moving the stick, does it hurt the clutch ?

[potownrob]

thanks for the quick reply ! I am currently doing adding gas after stick in the desired gear position, while still clutch in. Besides this is slower than adding gas while moving the stick, does it hurt the clutch ?

at what point you add the gas, in and of itself, has no effect on the clutch, so long as the clutch is fully disengaged (pushed in). now, if you let the clutch out slowly or otherwise botch the rev-match and slip the clutch into the lower gear with not enough gas there (something i refer to as braking with the clutch), yeah, the clutch is gonna feel it (though it can take the abuse in moderation unless it's already on its last legs). pretty much, if you don't get the rev-match right and timed right (which just takes time and practice), either the clutch is gonna feel it, or the rest of the driveline (engine, mounts, suspension, axles etc.) is gonna feel it. You will eventually get it down at least decently smooth, where there's some sort of balance between clutch wear and shock to the driveline. The clutch is designed to be one of the weakest links in the driveline to keep the rest of the parts from falling apart. that said, it's also designed to take some abuse.

[tankinbeans]

My opinion, and it took me awhile to teach myself, is that it feels better to do what you're doing - clutch in, move shifter to desired gear, blip gas, clutch out - because it ensures that you don't grind your synchros.

When I was trying to learn I'd try to blip the gas before the shifter was in gear, but my other leg would automatically come up on the clutch and engage it. Then when I went to put the shifter in the gear I wanted I'd get the grindy bit. Not a pretty sound.

I'm at the point where close is good enough for hand grenades, horse shoes, and downshifts.

[bk7794]

Sometimes I blip the gas right as I begin clutching out of the "dead zone" and right when I hit the biting point the engine either has a few hundred rpms to go or is dead on...but I make sure I am already in gear. Its hard to do that but when I time it and rev match perfectly the downshift is unfelt.

[theholycow]

I'm at the point where close is good enough for hand grenades, horse shoes, and downshifts.

This. However you prefer to do it is fine among the options discussed in this thread. There's no need for precision. Of course it can be fun to try to improve your precision but there's no need to agonize over it.

Sometimes I blip the gas right as I begin clutching out of the "dead zone" and right when I hit the biting point the engine either has a few hundred rpms to go or is dead on...but I make sure I am already in gear. Its hard to do that but when I time it and rev match perfectly the downshift is unfelt.

That's how I roll (except when double-clutching). I want to go straight to my target RPM without wasting time mucking about with other RPMs. I don't want to go vrooooOOOOoooomm, I want to go vroom. Minimal drama/noise, minimal wasted fuel, minimal wasted time; just straight to business and get back to what I was really planning on - accelerating.

[bk7794]

Sometimes I blip the gas right as I begin clutching out of the "dead zone" and right when I hit the biting point the engine either has a few hundred rpms to go or is dead on...but I make sure I am already in gear. Its hard to do that but when I time it and rev match perfectly the downshift is unfelt.

That's how I roll (except when double-clutching). I want to go straight to my target RPM without wasting time mucking about with other RPMs. I don't want to go vrooooOOOOoooomm, I want to go vroom. Minimal drama/noise, minimal wasted fuel, minimal wasted time; just straight to business and get back to what I was really planning on - accelerating.

Exactly what I was thinking! Also minimize the amount of heat the clutch has to disperse away.

[gundamz2001]

thanks for everyone's input! You guys are great.

It looks like it doesn't really matter when we blip the gas, as long as the clutch is in. But then why is double-clutching better ? I thought the difference between the two is that

for single clutch case, blip whenever the clutch is in

for double clutch case, blip when the clutch is out, and gear is in neutral, then clutch in again and move into gear.

If blipping the gas while clutch in doesn't hurt the clutch/synchro, why do we need to do the extra step for double clutch ?

Thanks again!

[tankinbeans]

Double clutching isn't "better" it's just different. Double clutching is more or less required for vehicles without synchros such as big rigs. Big rigs don't have synchros because they're too powerful and put too much strain on synchros. It can be helpful in a car with weak synchros, but it comes down to preference as to which you use. Depending on my mood I'll use either.

I know there are more specific reasons why one would need to double clutch, but the Spark Notes version is helpful too.

All the best.

[bk7794]

I double clutch when I am going into first and my speed is a bit too low for second.

[scionkid]

I usually ease into the gas as soon as the clutch goes dow and hold the gas down until the rev gets to where it needs to be. Blipping works for low speed downshifts. But for those times when I'm grabbing 2nd at high speed or shifting to first on the fly, where precise rev is required, I'd waste a little more gas to get my rev just right; blipping is kinda like shooting in the dark and hoping for the best.

[theholycow]

If blipping the gas while clutch in doesn't hurt the clutch/synchro, why do we need to do the extra step for double clutch ?

Double-clutching can get you into gear faster when you're doing a very big downshift, where you might have to wait a few seconds for the synchros to do their job with a single-clutch shift..

It can also be fun to practice. The skill can be useful if you ever drive a dog box (transmission with no synchros as found in big rigs and some race cars), a regular transmission whose synchros have been damaged, or if you ever need to shift without the clutch due to a clutch malfunction.

[Roger]

I prefer rev matching later rather than early, I usually rev match as the shifter enters the lower gear. When you rev match early you have to raise the RPMs higher to account for the drop in RPMs.