SMG II violent jerking back and forth!

Originally Posted by Pinecone

This has NOTHING to do with shifting. And it can happen with any clutch based system. It is a throttle based driver in the loop oscillation. And most times does not occur when shifting at all.

Driver steps on the gas, car moves forward, quickly, and driver moves back in seat, lifting foot from throttle. Driver pushes more to keep accelerating, but by the time the foot moves, the car has slowed and the driver moves forward depressing throttle, combined with foot movement makes too much throttle. Driver lifts foot, but body is moving back due to acceleration and lifts, combined with conscious lift lifts too mcuh, and so on, and so on...

Just wanted to say this is a great description. This is the first time on any forum anywhere I've heard this properly described. My 330i SP 5-speed does the exact same thing. It feels exactly like there's something wrong with the engine controller -- an oscillating surging. However it's driver induced oscillation.

Anybody experiencing this can verify it by noting the conditions where it occurs. If it's most common when accelerating briskly in 1st gear and hitting a bump, that tends to confirm it. The bump jostles your foot on the accelerator, which then sets up the oscillation. It's normal and there's nothing wrong with the car. It usually doesn't happen in 2nd or higher gears. It probably happens on SMG because it's more like a manual, but it's not the SMG transmission causing it.

It happens on BMWs, esp. manual transmission sport/ZHP package 3-series and M3s, because the suspension is stiff and the engine is very responsive. The suspension increases the chance of your foot jolting the throttle. It doesn't take much to start it. It might not happen as much on an automatic transmissions, which may buffer the throttle or upshift.

There may be other additional jerkiness from the SMG under some conditions, but the above driver induced oscillation is very common.

There are ways to prevent it and ways to stop it, as have been mentioned in this thread, but no way to make you not look like an a$$ when it happens

Originally Posted by Soylent

There are ways to prevent it and ways to stop it, as have been mentioned in this thread, but no way to make you not look like an a$$ when it happens

You get a bumper sticker that says, "It isn't my fault. My iDrive is defective"

Originally Posted by rumratt

You get a bumper sticker that says, "It isn't my fault. My iDrive is defective"

Lift off the gas when shifting. Just imagine that you are super fast at shifting so it only takes a quick lift of the throttle.

This will ensure a good shift.

It's very simple really if you have experience with manuals and treat smg as a manual that you don't have to push the clutch in with your left foot. Very simple really. I had no problems with the SMG from the get go cause I drove it like a manual.

Tangent: That being said.......I don't like SMG cause you have to drive it like a manual. What? you say, yeah day to day driving I find it tiresome and not as satisfying as shifting myself. Yes, it's less physical effort than pushing a clutch in but in regular driving I just find it annoying. If I didn't want to shift myself I would just get an auto. My opinon, SMG great for racing and track work but not so good on the street. On the track it is unbeatable. But really, how often do we track our cars? I don't live near the Nurburgring anymore so no more SMG for me.....

Some of us track out cars a lot. And I like it on the street. And the 330 SMG is NOT the same thing as the M3 SMG. BY A LOT.

And this problem can occur without shifting, just by hitting a bump in the road in 1st gear.

Originally Posted by MdCar

I have ordered 650 conv and have another week to finalize any changes. Been driving a Honda S2000 6 speed and really wrestling with 6 speed vs. SMG. Unfortunately only been able to test drive a 5 with SMG around the dealer's test loop. Previous 6 speeds who moved to SMG, would appreciate your candid comments.

Hi,
I'm from NOVA and just ordered a 650 coupe four days ago. How long do I have to make changes do you think?

Now to answer your question. I have an SMG II M3. I opted for the STEP in the 650. Few rambling reasons: The SMG isn't the same. Both paddles up shift and downshift the tranny. That differs from the SMG II or III systems where the left paddle downshifts and the right paddle upshifts. I didn't want the hassle of relearning.
Really looked over the STEP tranny. It's an awesome tranny that better suits the 650 in my view. Had it been available with SMG III I MAY have gone that way.

You also save $1,300 in gas guzzler fees with the STEP and don't have to worry about some bonehead valet not being able to drive it. I rarely valet park, but two or three times a year I've been forced to. Additionally, at work our parking attendants sometimes over book, so I've had to leave it with them briefly.

This is an auto car for 95% of America. You'd better lease it if you go SMG or your going to get hammered on resale.

Originally Posted by BigHat

You also save $1,300 in gas guzzler fees with the STEP and don't have to worry about some bonehead valet not being able to drive it.

This is an auto car for 95% of America. You'd better lease it if you go SMG or your going to get hammered on resale.

Maybe there are just more of them in Texas, but I haven't found a situation where less than two valets knew how to operate it. Even the guys at the car washes know what to do.

What he said...especially the "driver" and "and" parts.

It took me 2 weeks to be very smooth with it. But when I drive with flip-flops or sandals, the bucking will undoubtedly kick in. Best to get proper driving moccasins or shoes...have your right foot be one with the gas pedal.

Originally Posted by Pinecone

AGAIN, the jerkiness is NOT caused by the tranny, but by the DRIVER and the drive by wire.

wow... i thought it was just me. i had recently bought one and have experienced the jerking motion. it was quite embarrasing pulling out of a corner looking like a newb while i was trying to pimp my new car. i know we can all fight this evil force that jerks us all. good luck to all.

Originally Posted by AJAX

Maybe there are just more of them in Texas, but I haven't found a situation where less than two valets knew how to operate it. Even the guys at the car washes know what to do.

Valets will have to pry my (M3) car keys from my dead cold hands !

It's weird but I have yet to experience the jerkiness. Maybe it's because I am used to the Cobra which has a touchy/heavy clutch. I don't know. I do know it has happened to me when driving sticks when I first learned to drive. Fighting the bucking motion actually makes it worse since you respond too late and only increase the jerking.

I have experienced jerkiness, and it takes getting used to to get rid of. I have only driven manual cars for the 10 years that I have been driving, so the SMG was a change for me. I prefer a 3 pedal manual, as I don't track the car often enough and don't get stuck in traffic where a clutch would annoy me.

The biggest pain to me is trying to get the heel-toe action down on downshifts, especially to 2nd gear...you have to hold the gas pedal down for the car to blip the throttle, not just blip it yourself, which is counter-intuitive in a 3 pedal manual car when heel-toeing.

Opinions will vary on this, but the SMG is enough to make me want to trade the car for a true manual. I have been looking at e39 540i6 cars for a little bit and I will probably go with that. Take my $.02 for what it's worth, but I would think that people who love driving 3 pedal manual transmission cars will not enjoy this transmission very much unless they must have an auto or semi-auto car [for the wife, traffic, due to a handicap, whatever reason].

My advice to anyone considering an SMG is to spend as much time in it as possible prior to making a purchase decision.

Ferrari had/has the same tendencies in the old 360F1 transmission. The last 360 I drove however was a Challenge Stradale, and it did NOT seem to have the tendency to oscillate in first gear.
The best advice that I have read in this thread is to LIFT and UPSHIFT. Works every time!

Originally Posted by VentoGT

Take my $.02 for what it's worth, but I would think that people who love driving 3 pedal manual transmission cars will not enjoy this transmission very much unless they must have an auto or semi-auto car [for the wife, traffic, due to a handicap, whatever reason].

My advice to anyone considering an SMG is to spend as much time in it as possible prior to making a purchase decision.

You obviously haven't been reading the threads.

Many of us love and have 3 pedal cars, but still love SMG II.

Originally Posted by VentoGT

Take my $.02 for what it's worth, but I would think that people who love driving 3 pedal manual transmission cars will not enjoy this transmission very much unless they must have an auto or semi-auto car.

I beg to differ.

I believe that one will derive the most enjoyment from SMG if they are proficient in a standard manual trarnsmission.

Those who expect the transmission to behave like an automatic will be disappointed.

edit: never mind.

Originally Posted by plien69

I beg to differ.

I believe that one will derive the most enjoyment from SMG if they are proficient in a standard manual trarnsmission.

Those who expect the transmission to behave like an automatic will be disappointed.

Could not have said it better. I was always a die-hard manual guy (and still am) and didn't even think about getting an M3 with SMG until I ran into an M3 that was exactly the way I wanted it except for the SMG. I then tried it out for the first time and REALLY liked it.

If I understand it correctly, the auto-clutching mechanism tries to anticipate your intention. So if you press hard on the throttle in the 1st gear and then ease off, it thinks that you are about to brake. It disengages the clutch in anticipation of the braking. However, you continue to press on the gas, and it engages the clutch again. The cycle continues....

This is indeed a problem, but something which can be easily overcome by any of the three fixes (press on it, ease of it, shift up to 2nd). And I am glad it is not just a Z4 thing. And for the record, SMG, even the Z4 version, is the best thing since sliced bread.

WHen it has happened to me, there was NO evidence of the clutch going in or out of engagement.

ANd since the car perfectly happily engine brakes,I don't think it will disengage the clutch based on throttle position while in motion (other than at VERY slow speeds).

Originally Posted by Pinecone

WHen it has happened to me, there was NO evidence of the clutch going in or out of engagement.

ANd since the car perfectly happily engine brakes,I don't think it will disengage the clutch based on throttle position while in motion (other than at VERY slow speeds).

I don't think it does either.
I don't think it disengages. You can easily copy this behaviour on a manual (and people have including myself). It's just the throttle engaging/disengaging that does this.
I have yet to experience it on the SMG.

I can understand the clutch engaging and disengaging but what do you guys mean by the throttle engaging/disengaging?
Do you mean the TBW acting up or something more? Then how does it happen with manual cars or cars without a TBW?
And the car can not engine brake from the 1st gear, can it? (and the problem occurs only in the 1st gear).

Originally Posted by BayAreaBMWFan

I can understand the clutch engaging and disengaging but what do you guys mean by the throttle engaging/disengaging?
Do you mean the TBW acting up or something more? Then how does it happen with manual cars or cars without a TBW?
And the car can not engine brake from the 1st gear, can it? (and the problem occurs only in the 1st gear).

Has nothing to do with the Throttle by wire. It is simply a motion of throttle on/throttle off done by the driver. The jerking of the car will make your foot on the throttle do this. Trying to fight this motion makes it worse since you react too late and only increase the on/off motion.

Originally Posted by rruiter

Has nothing to do with the Throttle by wire. It is simply a motion of throttle on/throttle off done by the driver. The jerking of the car will make your foot on the throttle do this. Trying to fight this motion makes it worse since you react too late and only increase the on/off motion.

OK. Thanks for the observation. That explains the series of jerks.

However, the driver input happens only after the initial jerk. What causes the initial jerk?

In my experience, it is caused typically, when you are easing off the throttle after a hard start.

Originally Posted by BayAreaBMWFan

OK. Thanks for the observation. That explains the series of jerks.

However, the driver input happens only after the initial jerk. What causes the initial jerk?

In my experience, it is caused typically, when you are easing off the throttle after a hard start.

That's because you ease off and unknowingly start the motion. Remember, at higher rpm's the car can get pretty twitchy. A slight increase in throttle after easing off will easily do this. Make sure the Throttle itself is not defective. Check with the engine off if the pedal goes down smoothly without feeling 'steps' Best done without shoes.