match RPMs on *up*shift?

[drobbins]

What exactly are people talking about when they mention matching RPMS on upshifts? When downshifting I understand the concept of blipping the throttle to have a smooth shift and not upset the car when downshifting - but upshifts?

-Daniel

[tomauto]

Basically, it is letting off the throttle when you have the clutch pushed in so that the motor's revs will drop to the appropriate level before the higher gear is engaged.

[drobbins]

Aha. Thanks.

That's generally the way most people shift, isn't it? :)

[tomauto]

Yeah, basically...I don't know what all the fuss is about. It is just natural to let off the gas when shifting...

What is the alternative? Keeping the gas pedal floored and letting the motor bounce off the rev limiter? I think people are getting their ups and downs mixed around...

[physicns]

People do a thing called powershifting, where you basically keep the gas floored as you shift. You get a little power bump when you drop the clutch and can chirp the wheels, but it's pretty damaging to the synchros, clutch, and diff.

[meat]

With real powershifting you don't use the clutch.....

[repiv]

I don't know what all the fuss is about.
If I may elaborate..........................

There has always been discussions about how certain shifts are "notchy" or "crunchy" or even grinding when shifting. Lately, there has been a resurgence of this topic. "Matching revs" should not be confused with "Rev matching". Rev matching is almost always and traditionally associated with downshifting, while matching revs can apply to both down and upshifting.
Matching revs on an upshift is not always intuitive nor is it always a simple matter of taking your foot off the gas pedal and allowing the revs to drop. Timing is also key to a smooth shift resulting from a good match of revs. If you are driving sedately, you are likely able to let the revs drop to near idle at the time of the shift to the next higher gear. Also, it makes a huge difference whether or not the drivetrain is cold or up to operating temps. If you are driving briskly and are revving up to or near redline, then the revs that will match precisely to the next higher gear selected WON'T be at or near idle. It will be somewhere near VTEC range. If you allow the revs to drop to near idle in this circumstance by being too slow in the shift, then the shift will be rough, clunky and very unprofessional looking and sounding.
Each type of driving situation, be it normal, sedate driving or one that is more spirited or one that is all out "pedal to the metal" acceleration will demand a different level to rpm to match revs properly. I hope this illustrates that there is a bit of fuss, particularly if we are trying to convey the concept of smooth shifting to someone who is new to manual or someone who is having a hard time with our close gated, short throw, 6 speed transmission, which cannot be equated to most other manual transmissions that most people have ever driven.

[drobbins]

Repiv,

Good points.

OK, so let me make sure I've got this. I understand that between shifts, the engine RPMs are dropping. What you're saying is that if you shift at too low RPMs and/or too slowly then the RPM drop can be significant and result in a bad shift. Higher in the RPM band it's less risky.

OK. Think I got it.

Do you have any tips or examples of how you personally factor this into your shifting technique for sedate as well as spirited driving? I'd be interested in hearing an anecdote or something or habits you've formed to apply this knowledge. Or is it more of a "if you're doing it right, you'll get a good shift with no lurch or lag"-type thing?

[equinoxiq]

matching the revs on an upshift does not necessarily equate to spirited shifting. whenever i do it i feel it's very relaxed and natural. you just have to get used to the timing and then how you know you've done it right. but i never feel like i have to rush or something to make it happen. i think perhaps a systematic way of doing it would be to practice at a set speed and perform a shift let's say from 2nd to 3rd. ideally you should know what rpm's the engine would be in both of those gears and then see how long you have to wait when shifting to allow the engine speed to drop the appropriate level before you let off the clutch pedal. as you get better and more comfortable at that then you can see the differences in rpms throughout the range of all rpms

and you know you did it right when you the engine is put into the next gear and there's no sudden change of rpm as you're letting off the clutch pedal, and if that happens then you shouldn't have any 'lurch' or jolt. but let the rpm be the judge, not the lack of jolt... because you can perform a shift at all the wrong rpms and still have it be smooth if you're purposefully slow with the clutch pedal and make a seamless transition.

this is just what i've noticed from personal experience, it may or may not work for you but it's helped me be more consistent so far

[drobbins]

equinoxiq - thanks for the info, that was very helpful in understanding the practical aspects of this :) I need to look at a gear ratio chart now :)

[photodavo]

Daniel,

Check out one of Dave's earlier posts here. http://forums.s2kca.com/showthread.php?t=19625&highlight=snow+drags

They are all fun - most out playing in the snow with other S2000s but toward the end of the list he has examples of both upshifting and downshifting. I thought it might give you a better idea. :)

Hehehe - I beat Dave to linking to one of his own threads. ;)

[repiv]

Do you have any tips or examples of how you personally factor this into your shifting technique for sedate as well as spirited driving? I'd be interested in hearing an anecdote or something or habits you've formed to apply this knowledge. Or is it more of a "if you're doing it right, you'll get a good shift with no lurch or lag"-type thing?
I think you've already got the principles involved here. Now, putting them into practice requires time and just doing.
I've learned that when the engine is running just after a cold start, the colder it is out, the longer the cold high idle hangs before "kick down". During this time and the time just after this, when shifting and letting off the gas, the rpm tends to "hang" and is much slower at coming down. Depending on how you drive, you may have to alter the speed of the shift so that the rpm is just right at the moment you go into the next gear. Things change once the engine is up to operating temps. Revs don't "hang" nearly as much and they fall quite quickly. I drive by tach and by sound of the engine and exhaust. If I'm accelerating moderately and I'm getting up to about 5500 rpm in 1st, I know that when 2nd is fully engaged, the rpm will drop to about 3500. Well, I would try to engage 2nd the moment the revs fall to about 3500. Then, when I'm in 2nd and get to about 5500 and want to shift to 3rd, I know from experience that the rpm will be about 4000 in 3rd at that road speed. I try to let the revs fall to about 4000 at the moment the stick enters 3rd. The closer I can get to this rpm, the smoother the shift becomes. Of course, the clutch has to come upand gas re-applied at the same time before the revs drop too much further (that's when you get the "humpty dumps" and jerking). It's not always going to be right on, but it's something one strives to do. After a while, I don't even look at the tach anymore. I can tell by sound and feel that the engine is spinning at the right speed for the shift.
This same principle applies to a rev match downshift. With time and practice, we instinctively know just how much to blip the throttle based on what road speed we're going, what gear we're in and the revs start at to get the right rpm for the shift. It all comes with practice.

[hecash]

On shifting, if you do not lift when disengaging the lower gear, press the gearshift lever gently towards the next gear, say, with one finger, and then lightly lift on the throttle, the gear box will reach a "sweet" spot at the rev match and should slide into the next gear almost on it's own. Learn the sound and throttle feel from repitition and you've got a great shift.

Most of the beginners that I see at the track lift too much, too fast allowing the revs to fall past the sweet spot long before they try to engage the next gear.

[Hawkeye]

I think it was Jackie Stewart that discussed proper shifting technique. I recall him saying that a passenger shouldn't feel the car shift if done properly.

[whitemike711]

i have a question... and i hope im not thread jacking, but with all of this rev matching and matching revs and blah blah blah. Is it, it is not good to rev the engin? i know we do it to help "smooth" the transition on certain shifts, but is it still bad for the car?

[repiv]

Matching revs is never a bad thing. It's not quite the same as sitting stationary and revving the engine up to redline from idle with no load. Rev matching puts the load back at the height of the rev and it generally begins in the mid rpm range. Doing it right, you are only revving, at most, through about 4000 revs, as opposed to blipping the throttle at a stop light where you could be revving at much as 8000 revs and never putting a load on the motor.

[whitemike711]

so what happens when you do "sit at a light" and rev. what damage happens.

[repiv]

so what happens when you do "sit at a light" and rev. what damage happens.
When the car is operating "normally", even if it's just idling, the motor is pushing against some resistance. Forces are being applied to bearings, rods, etc in one particular direction. If you wildly rev a motor with no load, those forces begin to transfer to the opposing sides of those parts, thus putting undue and unnecessary stress, wear and tear on them.

An experiment you can conduct for yourself ............................
Go to a playground teeter-totter. Stand at one end and grab the end of the seat. Now, act like your arms are the reciprocation rods of an engine. Be careful not to smack yourself in the chin. Start bending your arms and straightening your arms to lift and lower your end of the t.t. Do it slowly at first. No problem, right? Now, speed up till you are going as fast as you can. At the bottom of the push (straight arms), the mass of the t.t. continues to go down as you change direction to come back up. This puts a pretty big shock on your shoulder sockets, doesn't it?
Next, securely tie a good amount of weight (that you can still manage) like 50 lbs to the other seat. Now go and repeat the same motion. At the bottom of the push, because there is load on the other end already trying to push against your arms, there is much less of a shock on your shoulder sockets when you suddenly change directions to come back. In the first example, you are quite able to use force to "pull" up on your end, while in the loaded example, yours arms are being assisted in coming back up. That's sort of what your engine goes through.

This is a pretty crude demonstration and I think you can find more technical and mechanical explanations on a Google search that would cover this subject far better.

[whitemike711]

no that's great. i have heard mix thoughts on this. i know sitting there and reving the engine is not good, but i just want to make sure im clear on exactly why. thanks for your help. and sorry if this was a jacking

[physicns]

On shifting, if you do not lift when disengaging the lower gear, press the gearshift lever gently towards the next gear, say, with one finger, and then lightly lift on the throttle, the gear box will reach a "sweet" spot at the rev match and should slide into the next gear almost on it's own. Learn the sound and throttle feel from repitition and you've got a great shift.

Most of the beginners that I see at the track lift too much, too fast allowing the revs to fall past the sweet spot long before they try to engage the next gear.

I'm not too sure I get what you're saying; from what I understand, when the clutch is disengaged (pedal down), the engine is not linked to the transmission; you can do what you want with the throttle, but it won't have an effect on speed of the transmission speed down. Something similar might make sense if you're doing clutchless shifting, but that's a field I have no experience in (except with 2-wheelers).