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3-Series (E46, E90) Chat relating to the BMW 3-Series from 1999 to Current. Models include: BMW 316i, BMW 318i, BMW 318Ci, BMW 320i, BMW 323i, BMW 325i, BMW 330i, BMW 328 Ci, BMW 328i, BMW 325i/xi, BMW 330Ci, BMW 320d, BMW 330d, BMW 335d.

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Old 07-23-2004, 12:15 PM   #1 (permalink)
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(*This is regarding the SMG on the 330Ci)

I've found that when shifting from 1st to 2nd in manual sport mode, it almost "kicks" me into 2nd gear. However, when in manual reg mode, the shift is smooth. (releasing pressure from accel pedal for both modes) I read that shifting from 1st to 2nd is better at and above 3k RPM. Nonetheless, I still get an unwanted smack when shifting in sport mode only in 1st to 2nd. Should I only use sport mode when in 2nd gears and above? Or is there something wrong? I don't remeber it always being so rough. As a newbie SMGer, I'm would appreciate any advice. Thanks.
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Old 07-23-2004, 12:53 PM   #2 (permalink)
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i have a 330 but with the manual transmission, maybe i am imagining it but my shifts from 1st to 2cd also seem more rough than any other shifts used
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Old 07-23-2004, 12:58 PM   #3 (permalink)
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Interesting. Though the SMG is a different, but similar beast, at least I'm not the only one with this conundrum. Anyone else have any input? Perhaps how I can alter my driving style to accomodate for the 1st to 2nd smack? Thanks in advance.
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Old 07-23-2004, 09:53 PM   #4 (permalink)
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Well, hello. 1st post. I have ordered 04 330Ci w/ SMG as well (arriving in September . . . )

This is my 'guess' since I have not tried SMG yet.

Regular mode being smoother > in this mode, SMG releases the clutch rather slowly and therefore engine's 2nd gear output matches driveshaft speed smoothly.

Sport mode engaging abruptly > in this mode, BMW's claimed gear change time is 'less than 150ms'. 1st gear to 2nd gear change has greatest gear differential. ie. on 330Ci,

1st Gear = 4.23 (Rocking!)
2nd Gear = 2.50 (diff of 1.73 from 1st Gear)
3rd Gear = 1.66 (diff of 0.84 from 2nd Gear)
4th Gear = 1.23 (diff of 0.43 from 3rd Gear)
5th Gear = 1.00 (diff of 0.23 from 4th Gear)
6th Gear = 0.85 (diff of 0.15 from 5th Gear)
(Reference, Final Drive Ratio = 3.38)

What does all this mean in simple terms? If you are driving in 1st Gear at 4.23x1000 = 4230 RPM, when you change gear to 2nd Gear, matching engine speed should be 2.50x1000 = 2500 RPM.

Now, I am assuming all this based on what I know about 330Ci and manual speed (BTW I have been driving manual since 1989). So you are going to have to verify this yourself.

In my current Honda Civic, 1st > 2nd is about 1000 RPM. That means drivers used to typical cars may have difficulty adjusting to 4230-2500=1730 RPM drop while shifting from/to 1st & 2nd. Therefore, if you are not matching this speed perfectly, one can only assume that the clutch engagement will result in a little jolt.

That said, if you are driving hard, I would like to have engine RPM to be slightly higher than what it should be so the car would take off immediately upon engagement.

I would really appreciate it if you could try it out (sorry for asking you to be a guinea pig) and confirm my assumptions. Can't wait to try it out for myself.
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Old 07-25-2004, 04:11 PM   #5 (permalink)
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I don't mind being the guinea pig. I love any excuse to drive my car. I tried shifting at the speeds you recommended and it didn't help with the "smack" all that much. However, it did go from 4200 to 2500 as you surmised. I think there may be something wrong with my car. If not, I guess I'll just live with the kick. I personally don't mind it, but when I have passengers, it's not the smoothest ride at low speeds. I scheduled a service appointment, so hopefully they can figure it out. I also have this whooshing sound that they are going to look at. Hope all will be good then. Let me know if you need me to experiment anymore.
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Old 07-25-2004, 09:32 PM   #6 (permalink)
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1. If you could, when SMG shifts from 1st (4230 RPM) to 2nd (2500 RPM) in sport mode, does it engage the clutch immediately (at about 4200 RPM) or does it try to match 2500 RPM before engaging clutch?

2. This 'kick' you are describing, is it like a sudden short burst of thrust, or like a sudden short burst of braking? Or is it like a kick to the transmission?

3. BMW information on SMG (on both 3 series and M3) states "gear shifting without lifting foot from gas . . ." Did you keep your foot on gas during shifting or did you lift?

My understanding of SMG operation from reading numerous review of SMG fitted 3 series is that it is to be driven like a race car in Sports mode. ie. Foot to the floor type of acceleration at race track or highway on ramp.

M3 SMG also, I've read, is rather harsh (abrupt & direct) in shifting in sportier modes. However, M3-SMG has 11 different modes, 6 being manual modes of increasing 'sportiness'. 3 series SMG has . . . let me see . . . 3! Automatic, Manual & Sport. I am guessing here, but I think the BMW engineers probably have only included 2 extreme modes of manual shifting, Manual = most subdued shifting, Sport = fastest but also harshest shifting.

I would try a hard acceleration gear shift test. Personally, I would accelerate very hard and shift at 6000 RPM and re-assess the kick. Let me remind you that this is YOUR car if you decide to try it out (ie. please don't blame me . . . when something goes 'BANG'). Also, watch those speed limits . . .
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Old 08-06-2004, 09:01 AM   #7 (permalink)
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Sorry for the delayed reponse. Been busy. Anyhow...to answer your questions...

1. If you could, when SMG shifts from 1st (4230 RPM) to 2nd (2500 RPM) in sport mode, does it engage the clutch immediately (at about 4200 RPM) or does it try to match 2500 RPM before engaging clutch?

It engages the clutch almost instantaneously after I tell it to shift. Not at 2500RPM.

2. This 'kick' you are describing, is it like a sudden short burst of thrust, or like a sudden short burst of braking? Or is it like a kick to the transmission?

It is like a combination of all of the above, with a little snap. Not as comfortable as in Reg mode.

3. BMW information on SMG (on both 3 series and M3) states "gear shifting without lifting foot from gas . . ." Did you keep your foot on gas during shifting or did you lift?

I lift it from the gas pedal, otherwise the whole car "breaks" while the gears shift. You'll see when you get yours. It's as lousy as when you keep your foot on the pedal in Auto mode. You have to lift your foot, at least a little, or you feel like there is an amateur stick shifter at the wheel, just learning to drive for the first time. (minus the stalling :lol: )

I just got my car back from the dealer yesterday evening to try to fix a whooshing sound I was hearing. They did and it also seems to shift a little better now. It certainly feels better when I have to cruise in 1st and 2nd in traffic.
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Old 08-06-2004, 10:55 AM   #8 (permalink)
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Well, words can only communicate so much. I am going to have to wait another 6 weeks or so before I actually try it out myself. I won't have any chance to take the car to the track this year but it will see some track time come May '05.

Meanwhile, I don't quite understand what you mean by 'whole car breaks while the gears shift'.

Using my logic, if the SMG re-engages the clutch immediately upon upshift to 2nd gear (within 150ms) and if you are lifting your foot off the gas pedal, I would think

1. Car would suddenly lunge forward because of engine momentum at higher RPM in 1st gear

2. Car would then lose momentum very quickly and engine brake, causing the car to slow down (remember that 2nd gear is still relatively high so engine braking will be pronounced as well)

3. If you are applying gas in step #2 above, that would make the gear change very jerky.

4. You also need to consider torque availability as well. Max. torque on M54 is at 3500 RPM. Therefore if you are changing gears at 3500 RPM in 1st gear, you will undoubtedly fall into lower torque zone.

I assume your description of amateur gear shifting as being 'jerky' but in a race car with heavy clutch springs, that's what you get. The fact is, if you up shift from 1st gear at 4300 RPM up to 2nd gear with no time to bring engine speed down to 2500 RPM, there WILL be a jolt. I think the most logic to me is to maintain the gas pedal position through the gear change (it's only 150ms, you cannot red-line within 150ms).

How about keeping a mid-level throttle in 1st gear (moderate acceleration) and trying shifting to 2nd with no gas pedal movement (keeping it constant)?
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