I've taped this to my dash, temporarily...

"With-a-G is back to not having anything written after his username" (with-a-g) 06/02/2014 at 16:06 • Filed to: None

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...as a corner-of-the-eye visual aid to rev matching.

I'm determined to get this perfect.

Every time.

deekster_caddy > With-a-G is back to not having anything written after his username 06/02/2014 at 16:08

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Practice. Just practice. There's no time for this.

Here's a great way to practice - only use the clutch for starting from a stop. If your clutch hydraulics have left you completely, just stop, put it in 1st, start the car, then carefully match each gear or call a tow truck. The starter has plenty of power to get you moving.

Yes, I've been there. No, I didn't call a tow truck.

Yowen - not necessarily not spaghetti and meatballs > With-a-G is back to not having anything written after his username 06/02/2014 at 16:08

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What do these numbers represent?

davedave1111 > With-a-G is back to not having anything written after his username 06/02/2014 at 16:08

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I just do it by sound. Subconsciously, that's how I decide when to change gear anyway.

HammerheadFistpunch > With-a-G is back to not having anything written after his username 06/02/2014 at 16:09

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Nah, Im just kidding. Best of luck nailing that rev match!

davesaddiction @ opposite-lock.com > HammerheadFistpunch 06/02/2014 at 16:13

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I am so glad to have this GIF.

Louros > With-a-G is back to not having anything written after his username 06/02/2014 at 16:21

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real127 > Yowen - not necessarily not spaghetti and meatballs 06/02/2014 at 16:48

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I too would like to understand how to read this diagram.

real127 > With-a-G is back to not having anything written after his username 06/02/2014 at 16:50

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OP please explain.

Chuck 2(O=[][]=O)2 > With-a-G is back to not having anything written after his username 06/02/2014 at 16:57

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You'll have it down by ear in no time, that's for upshifting and downshifting.

tromoly > With-a-G is back to not having anything written after his username 06/02/2014 at 16:59

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You don't need to get that complicated, in my experience just blip your throttle until the revs are high enough then let out on the clutch so it catches the engine on its way down at the proper RPM. Works for me no problem.

With-a-G is back to not having anything written after his username > Yowen - not necessarily not spaghetti and meatballs 06/02/2014 at 17:52

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I did this because the ratios from one gear to the next are different between each pair of adjacent gears, so the amount of tach movement differs if I'm shifting 4->3 or 3->2 for example. I have been working on rev matching for a while, and it got to the point where I hate making the mere "pretty good" match that I can barely still feel some drivetrain shock from.

The columns visually represent the relative ratios from one gear to the next adjacent gear. (Absolute gear ratio numbers available here ) I used colored bars so I can judge the proportions (e.g "30%") easily in my peripheral vision. I added the numbers (think of them as percentages if you move the decimal) to help with precise memorization. The divided colors within each column represents ratios of RPM changes for upshifts and downshifts. The bottom two numbers add to 100%, and the top number is the same fraction of the whole as the middle number is to the bottom number. It's the same information both ways, but rescaled so that I always consider 100% to be the initial state of the tach.

For example, if I'm upshifting from 3rd to 4th, I use the third bar. My initial RPM state, whatever it may be, is the top of the green bar. I push the clutch and let off the gas, the RPMs drop 25%, which I eyeball as the tach needle dropping that analogue amount to the top of the blue bar, at which point I can re-engage the clutch as suddenly as I want and get back on the gas with no drivetrain shock.

Example 2: downshifting 4th to third, same column, only this time I'm going to need to know how much blip will yield a perfect match. My initial state is again the top of the green bar, and when I dip the clutch, I blip the throttle to get another 33% higher before re-engaging.

This is the important mode of use for me (high-RPM downshifting) because I need to eyeball the correct amount of headroom to leave below the redline before attempting the shift. The situation is very different for a 2->1 shift than for a 3->2 shift, and this keeps me off the rev limiter for that particular situation.

With-a-G is back to not having anything written after his username > deekster_caddy 06/02/2014 at 17:53

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This is not what's going on here.

Drakkon- Most Glorious and Upright Person of Genius > With-a-G is back to not having anything written after his username 06/02/2014 at 22:59

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Actually, he is right. It is what's going on here. If you are accelerating hard, and you try to pull the lever out of gear and into neutral, it's really hard to get it to let go. The gears are meshed with the backs of the gears being driven pushing against the faces of the road gears. If you lift off the gas for just a second, the forces acting on gear faces is relieved and the shifter falls into neutral with no effort. The net forces of the engine speed falling (drive gear) and the momentum of the car moving forward (road gear) are even and it slips right out.

Likewise, if you are coasting, and try to force the shifter into gear, it will grind and grind and eventually go in. This is because the grinding is (painfully) matching the speeds of the gears and they will eventually mesh. Now the faces of the drive gear are trying to mesh with the backs of the road gears, but again, the forces don't match so it will not slip in until the grinding gets all the pieces synced.

If you start from a stop with the clutch and get moving, then accelerate hard for 3/4 - 1 second, the slip into to neutral, then as the revs fall, slip the shifter into second, you will discover, they match your chart very closely. This is easier to learn gently. I have a seventeen mile commute and if the stoplights are timed in my favor, I can get through neighborhood streets, thoroughfares, interstate, back to thoroughfare, back to industrial park street and never touch the clutch.

What he means my practice is these matched forces yield the no-lurch, rev-matched downshift you are looking for. By practicing this, you will learn intuitively where that match is, how much throttle it takes to get from Third to Second in a 50mph corner as opposed to a 35mph corner. You'll drive my your ear instead of looking at your tach. You're looking for the balance of forces. Better to have your eyes on the road than the dash.

With-a-G is back to not having anything written after his username > Drakkon- Most Glorious and Upright Person of Genius 06/03/2014 at 10:28

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No. Since I'm the one driving, I know what the issue is. I am not griding gears; I am not having any difficulty starting from a dead stop. The "problem" this is trying to solve is so minuscule and nitpicky that virtually no one else would think it a problem.

I am merely trying to perfectly match the speed of both sides of the clutch disks before engaging them. I am basing the method off of relative ratios so that it will become more intuitive at every speed. I am using analog bars so that it is not distracting. This works well for me as a mental model, though it may not help anyone else.

With-a-G is back to not having anything written after his username > Drakkon- Most Glorious and Upright Person of Genius 06/03/2014 at 12:28

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Maybe the confusion is about what I am trying to optimize. This isn't track duty, it's street driving, and I want to minimize jerk. I can bang-shift when I want to, but I use my clutch so I don't break the real or metaphorical groceries in the passenger seat.

But, in more "spirited" situations, I have also had a few frights while shifting in the middle of variable radius turns and breaking my tires loose from the torque delta. This will help remedy that.

Drakkon- Most Glorious and Upright Person of Genius > With-a-G is back to not having anything written after his username 06/03/2014 at 12:50

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Process is the same, spirited, track or commute. It's calibrating the tap on the throttle to not get the lurch. When the consequence is grinding sounds coming from under the floor, you calibrate very quickly. I rev match every downshift, whether I am clutchless shifting or not. Just a habit and one that makes the drive more pleasant for everyone in the car.

and 100 more > With-a-G is back to not having anything written after his username 06/04/2014 at 11:01

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I see what you're doing; you've done the number-crunching, and this is just your mnemonic to remember what you've learned. I think people assume you're consulting the chart everytime you shift. My brother has always done stuff like this, which didn't make sense to me ( "just fucking do the damn thing, man!" ), but its a step to get from concept to rote memorization. Some people are physical learners, some are visual... you know what you're doing.

For what its worth, my brother went on to study in astrophysics (specifically, black hole theory). Dunno if that justifies your method, but its just fun to brag on my baby brother. :)

With-a-G is back to not having anything written after his username > and 100 more 06/04/2014 at 11:42

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Well I'm a physicist by training and a visual learner, so there you go.