How do you safely accelerate hard with a MT?

My BMW is the first manual transmission car I've owned. When learning to drive it, mostly out of a desire to treat it as gently as I could, I paid special attention to always shifting smoothly. I've gotten pretty proficient at it, and both my up and down-shifts are usually undetectable (except for the unavoidable brief loss of acceleration).

A side effect of this is that I _always_ rev-match when up/down-shifting, no matter how hard I want to accelerate. But this seems rather...stupid, especially in the lower gears, because revving to 6500 in 1st means a looonnnng pause until the engine drops to whatever the appropriate RPM is in 2nd. Especially when merging onto the highway from a dead stop, the delay this produces is irritating.

The problem is, I always feel like I'm damaging something when I try to shift quickly, and just drop the clutch immediately once the shifter is in gear (rather than waiting for the RPMs to fall). But reading on this message board and others, it seems like lots of people (perhaps most) accelerate like that with their cars daily, with no ill effects.

So, my question is: how bad for the car is it to upshift in the manner I described (by not waiting to for the revs to fall)?

You'll find that it's not too hard to ease the clutch out as a means of decelerating the engine.

Slow disengagements of the clutch result in more slippage which results in more wear. Learn to shift and engage quickly, but smoothly. There shouldn't be much of a lurch, especially when upshifting to gears 3-6. You'll obviously need to be a bit slower on the engagement for first and a bit for second. Everything else you should be able to flick off. If you are downshifting, then learn to double-clutch downshift to smooth the engagment with a quick clutch release.

In the end, the quicker shifts are better for you clutch disc.

Also, after rereading your post, don't worry about rev matching on the upshifts. Shifting faster will automatically take care of that because you'll catch the next gear before the revs drop too much.

Originally Posted by xspeedy

Slow disengagements of the clutch result in more slippage which results in more wear. Learn to shift and engage quickly, but smoothly. There shouldn't be much of a lurch, especially when upshifting to gears 3-6. You'll obviously need to be a bit slower on the engagement for first and a bit for second. Everything else you should be able to flick off. If you are downshifting, then learn to double-clutch downshift to smooth the engagment with a quick clutch release.

In the end, the quicker shifts are better for you clutch disc.

Breaking the tranny is better than breaking the clutch?

Originally Posted by Nick325xiT 5spd

Breaking the tranny is better than breaking the clutch?

A typical manual gearbox is very robust. The transmission is for the gear selection. The engagement is all clutch / driveline.

Besides, most BMWs have the CDV, which softens the engagement anyway. No point in adding any more slippage.

Originally Posted by xspeedy

A typical manual gearbox is very robust. The transmission is for the gear selection. The engagement is all clutch / driveline.

Besides, most BMWs have the CDV, which softens the engagement anyway. No point in adding any more slippage.

If you're going to sell the car befor ethe warranty runs out, your way is better. However, your method basically involves shifting like SMG. Guess what? I broke my tranny at 4K. And this is NOT uncommon. I know of one guy who broke THREE trannies in his M3.

Originally Posted by xspeedy

Slow disengagements of the clutch result in more slippage which results in more wear. Learn to shift and engage quickly, but smoothly. There shouldn't be much of a lurch, especially when upshifting to gears 3-6. You'll obviously need to be a bit slower on the engagement for first and a bit for second. Everything else you should be able to flick off. If you are downshifting, then learn to double-clutch downshift to smooth the engagment with a quick clutch release.

I can already upshift and downshift smoothly, heel-toe, rev-match, double-clutch, and all that. That's not what my question is about.

Also, after rereading your post, don't worry about rev matching on the upshifts. Shifting faster will automatically take care of that because you'll catch the next gear before the revs drop too much.

That was the point of my question - is it bad to catch the next gear before the revs drop enough? When I say I rev-match my upshifts, I don't mean I blip the throttle to keep the RPMs up because I shift so slowly they've dropped by the time I get the shifter into gear, I mean I wait until the RPMs have dropped to the right point before letting the clutch out.

Basically what I'm saying is that currently, every time I engage the clutch I try to have the RPMs exactly where they should be, so that there's no clutch wear at all. Except when getting moving from a dead stop, I treat the clutch almost as on-off switch - I never slip it. What I'm asking is how bad it is to slip the clutch on upshifts, rather than waiting for the revs to drop enough (because that takes forever, especially in lower gears).

Slipping the clutch is fine. Banging the gears may lead to premature transmission failure. Clutches are cheap, transmissions are not.

Originally Posted by avalys

Basically what I'm saying is that currently, every time I engage the clutch I try to have the RPMs exactly where they should be, so that there's no clutch wear at all. Except when getting moving from a dead stop, I treat the clutch almost as on-off switch - I never slip it. What I'm asking is how bad it is to slip the clutch on upshifts, rather than waiting for the revs to drop enough (because that takes forever, especially in lower gears).

Yep, some slippage is fine. That slippage is mimimized with your on-off technique.

Originally Posted by avalys

Basically what I'm saying is that currently, every time I engage the clutch I try to have the RPMs exactly where they should be, so that there's no clutch wear at all. Except when getting moving from a dead stop, I treat the clutch almost as on-off switch - I never slip it. What I'm asking is how bad it is to slip the clutch on upshifts, rather than waiting for the revs to drop enough (because that takes forever, especially in lower gears).

Hahaha Avalys, I was going to say that you sound like an engineer, then I look up and see you're at MIT. Try thinking of the clutch as an inverter. In an ideal world it would be on/off. But in reality, that will never happen, there will be a transition period where both transistors are on (ie clutch slipping). Yeah some extra heat is wasted, but it's ok for both the clutch and the transistor. Just don't keep the clutch slipping for long periods of time. It'd be like having both transistors in linear region, burning crazy amounts of power, but not doing a whole lot of the rest of the circuit.

End Nerdy discussion here!

IMO, don't pay attention to the revs dropping on upshifts -- "just do it"! It seems like you might be trying too hard to perfect the whole shift scenario...

You seem to have pretty well mastered all the basic mechanical functions....now just try executing them in a crisp, faster manner, but without being overly forceful. Don`t be concerned about premature clutch wear....it`s not gonna happen. Unless your faster shifts elicit rude noises from the trans, you`re doing everything OK.

Regards,
Bob

Originally Posted by Nick325xiT 5spd

Slipping the clutch is fine. Banging the gears may lead to premature transmission failure. Clutches are cheap, transmissions are not.

Hi, I know next-to-nothing about this stuff. If I understand your post, when I downshift from 6th to 4th on the highway, I should use the clutch to smooth out the downshift?

Thanks

Originally Posted by avalys

I can already upshift and downshift smoothly, heel-toe, rev-match, double-clutch, and all that. That's not what my question is about.

Excuse me.. but if you have already mastered those advanced techniques, why do you need to ask such a seemingly simple question?

No matter what you do, clutch slippage will always occur to create a smooth shift. That's from my experience. The CDV makes sure of that.

People who rev up to 6500rpm and drop their clutch are the ones who "burn rubber" on the shift. From my understanding, slipping the clutch to ensure smooth delivery of power will result in quicker speeds.

Lastly, I don't think a manual can ever be as smooth as an automatic. Trying to be that smooth is unnatural.

Hi avalys

It sounds like you are light years ahead of others in learning smooth shifting this early with a manual. This is especially laudible considering the E46 drive by wire throttle and clutch delay valve make old timers lurchy at times.

I agree that using full torque and full revs and then wasting over what seems like much more than a second shifting to 2nd gear seems silly - why push so hard if you aren't going to use the time "saved" accelerating hard?

I find my 330i way more difficult to drive balls out and smoothly than my 96 VR6 Passat. With the Passat I just let the clutch out quickly and smoothly to drop the revs faster after shifting and open the throtte wide just as the clutch is completely coupled. There is no lurching, no shock; just a short pause while out of gear declutched.

Most of my spirited driving with the 330i involves shifting at about 4500 RPM with shift and clutch timing that is gentle yet just long enough to catch the revs for perfect matching without any shock or even the need to blip the throttle to get the revs back up. When revving out to 6000 RPM in first wide open, the revs do take too long to drop, but if you just took a gap in traffic and don't want to get rear ended you haver to get back on the power sooner and just have to let the clutch out more deliberately.

The links to the videos below show video of gentle, moderate and agressive launches. Most of my driving is like the moderate launch and shifting shown unless boxed in by traffic and gentle is all there is room for. Hard launches and shifts shown in the "agressive" video are OK for the race track, but seem a little too abrupt for every day street use, but it certainly gets you moving in a hurry:

Introduction page
http://www.bmwm5.com/greg/school/

Video menu page
http://www.vidload.de/script/kategor...&sort=filename

Moderate launch
http://www.vidload.de/script/load.php?fileid=7

Agressive launch
http://www.vidload.de/script/load.php?fileid=8

Gentle launch
http://www.vidload.de/script/load.php?fileid=6

Enjoy!

Originally Posted by allaboutme

Excuse me.. but if you have already mastered those advanced techniques, why do you need to ask such a seemingly simple question?

His question is valid, I think, and I've wondered about it myself.

Restated: How should one make the shift from 1st gear at high rpm (6500+) to 2nd gear (~3500 rpm), balancing shock/wear to the drivetrain with acceleration time? Specifically, how bad is it to let the clutch out quickly without waiting for revs to drop, compared to letting the clutch out a little slower without waiting for the revs to drop?

FenPhen, I didn't mean to tone the post so maliciously. The fact is the person claimed to know heel-toe and double clutching which are basically the advanced techniques in driving a manual. He posed a question that seemed either unnecessary or was exaggerating what he could do with his car.

Anyway.. I, too, have noticed this 1st to 2nd problem. Indeed, I do have to pause momentarily to let the revs drop but it doesn't seem too long with some practice. Like I said, I would slip the clutch and they will hook up providing a nice constant thrust of acceleration even with the pause. And when I say slip I mean a quick yet smooth. Otherwise you can just completely drop the clutch and let the drivetrain take care of the stress and tires handle the rest.

Upon rereading his post, I surmise he looks at the tachometer too often. Go with the flow, I say.

Originally Posted by stephen05zhp

Hi, I know next-to-nothing about this stuff. If I understand your post, when I downshift from 6th to 4th on the highway, I should use the clutch to smooth out the downshift?

No, rev-match: clutch in, use the gas pedal to quickly bring the engine revs to a higher speed that matches the lower gear while you do the shift, clutch out. Let the clutch out slowly to minimize shock from a missed match. As you get better at rev-matching, you can let the clutch out faster.

Be very careful downshifting into 4th: make sure you're going into 4th and 2nd. Whenever you shift into 4th or 3rd, don't push the stick left at all and don't touch the stick from the right side. Let the gear selector center itself in front of 3rd/4th and you supply just the vertical force.

I have never put this much thought into shifting.

My advise is to do what "feels" right.

Originally Posted by stephen05zhp

Hi, I know next-to-nothing about this stuff. If I understand your post, when I downshift from 6th to 4th on the highway, I should use the clutch to smooth out the downshift?

Thanks

I would not recommend that. You should double clutch to help in rev matching. Shift into neutral and let go of the clutch pedal. Then blip the throttle (how hard depends on how big the downshift and your road speed), and then engage the lower gear normally. You'll have to be decently fast about everything to keep the revs from dropping too low.

Originally Posted by xspeedy

I would not recommend that. You should double clutch to help in rev matching. Shift into neutral and let go of the clutch pedal. Then blip the throttle (how hard depends on how big the downshift and your road speed), and then engage the lower gear normally. You'll have to be decently fast about everything to keep the revs from dropping too low.

Double clutching is completely unnecessary in today's cars.

Just rev match with the clutch pedal in.

Originally Posted by allaboutme

Excuse me.. but if you have already mastered those advanced techniques, why do you need to ask such a seemingly simple question?

I've had the car since November of 2003 - that's what, about 16 months? I already knew the basics of how to drive stick before I got it.

I've put about 30,000 miles on the car since then, so I've had plenty of time to practice...but all my practice has been by myself, and I've had no one to tell me the finer points of what the "proper" way to drive a manual is. I heard about double-clutching, heel-toeing, etc. on this message board, but more subtle stuff (like this topic) is harder to pick up online.

Like I said, I've always assumed that clutch slip = bad, and tried to minimize it as much as I could.

Originally Posted by allaboutme

Upon rereading his post, I surmise he looks at the tachometer too often. Go with the flow, I say.

Hah, you're right. I know I do. But like icemanjs4 says, I'm an engineer - I have a hard time ignoring any sort of number, gauge or readout.

The drop in gearing between 1st and 2nd is large which causes most of the problem, if you think it's bad with the 5MT you'll be surprised to know it's even larger with the 330's 6MT. Just keep practicing and getting the feel of it. You can do an instant shift at redline in 1st by declutching, pull the shifter to 2nd and instantly let the clutch up and floor the gas at the same time. This will put some wear on the clutch, and if you're not careful you will put the most stress on the drivetrain. Or you can pull the shifter into second, and smoothly but quickly let the clutch out and give it a little gas at the same time to maintain momentum, but make sure you don't give the car any significant throttle until the clutch completely hooks up, or wait until the 3K rpms drops and then engage the clutch for second. I usually use the rev-matching method to reduce wear, but if I have to accelerate harder I will use any of the first two methods depending on the situation. The thing to remember is you don't want to bang the clutch, and you don't ever want to be giving the car a lot of throttle while the clutch is slipping. Most of all just drive by feel, eventually you will be able to do this. And also work up to this, just get used to driving normally, then increase your speed and acceleration little by little, take your time and it will become second nature. Also, the 330i is really geared more for high speed highway driving, it's not a good drag racer. Once your rolling the 330i is good and the shifts from 2 - 6 should be easy to do and fast if you desire, but the 1st - 2nd redline shift from a complete stop is tricky, takes practice and like I said, don't forget you're driving a 330 and not a Corvette or Mustang.

Edit - If you have a CDV remove it, doing that will make the clutch behave more consistently.

edit - I realized you have a 325 but what I said about the 330 also applies to your car.

Originally Posted by avalys

Like I said, I've always assumed that clutch slip = bad, and tried to minimize it as much as I could.

Generally, slipping the clutch is bad, but it can't be avoided. Even starting in first the clutch will slip, right?

To make the transition from 1st to second I redline then clutch in.. pause.. revs will begin to drop.. pull into second..feed a modicrum of gas to maintain momentum and rpm and ease the clutch out in one smooth motion... yeah i can feel the clutch slipping through the pedal but then its for such a brief period... like someone else said, don't worry too much about it.. you could always switch up to second around 5000rpm so the rpm drop wont be as severe.. and in second gear you'll still be in the optimum range so you're good to go.. i doubt most people will at that instant merging onto a freeway will be drag racing you up...