DIY : SMG gearbox maintenance

Discussion in 'E36 / E30 FAQ' started by thvdevel, Mar 12, 2016.

  1. 12 Mar 2016 at 10:52 PM #1
    thvdevel

    thvdevel Rocking a new hat

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    Hello everybody,

    I have taken the time this afternoon to write down a little DIY about SMG 1 gearbox maintenance.
    Hopefully it will help SMG 1 owners (if any), and was really worth it :)

    [​IMG]

    Please have a look in my car thread for those interessted (post#27, page 2)
    => http://forums.m3cutters.co.uk/showthread.php?t=137908


    :thumbsup:
     
    Last edited: Mar 12, 2016
  2. 15 Mar 2016 at 12:31 AM #2
    MParallel

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    Great work! I bought a new can of Pentosin too long ago. Still need to change it.

    As you say, you can't just change everything at once. So you would need a few bleed/venting sessions to get all the old oil into the reservoir.

    I also noticed you can do the venting a couple of times, with each time more and more air being removed.

    Oh man being able to do this at home at any moment you need/want to, saves so much time and money.

    I hooked mine up to DIS this weekend as well and did the readaptions. Not the bleeding as it's not needed atm.

    Did you also check the clutch? If you go into the diagnosis section and select clutch, it will tell the state of the clutch:

    "The clutch is okay"
    [​IMG]

    I checked but SMG1 has no specific clutch bitepoint adaption/learning option like SMG2. I guess it's part of the other adaption program.

    I replace my accumulator not too many km ago. yes it makes all the differences.

    I really enjoy the gearbox. It's not slow by any means. It's no DCT, but if you keep that in mind. If you floor it and don't even lift, shifts are fast.

    Do you realise that full throttle is pedal to the kickdown and kickdown switched pressed?

    I always thought it was just used in auto mode, but it actually switches to another mapping. Also when you check the TPS sensor readout in DIS, which I did last weekend. If you press the pedal down, but not the kickdown switch, it is 96% open. And with kickdown depressed, 100%.

    If you haven't tested yet, do so and be surprised at the fast shifting.

    Some guy over here, who's driving an SMG1 for over 10 years, told me the SMG1 even revmatches. I doubted as I have no documentation whatsoever that mentions this, but I have noticed in the past revs rising and that is before the clutch closed. He says the ICV is used for this. Plausible for sure.

    As you say, SMG1 has no shiftspeed button like SMG2 so you can't have lighting fast shifts when driving like a nanny. I'm not even sure that would be a joy to drive.

    I did have this brainfart. What would happen if the kickdown button was pressed, but the throttle not fully down (bridge the switch). Would it give an error or would it, and that would be a big one, go into its fast map and shift faster while not flooring it.

    If that would even work, this would in theory mean you could make a switch to switch between 2 shiftspeeds. I haven't tested this yes, but that would be one major SMG1 hack never tried before.

    Bottom line. SMG1 is great. It's a fun system and ahead of its time.
     
  3. 15 Mar 2016 at 10:59 AM #3
    thvdevel

    thvdevel Rocking a new hat

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    Yead defintely change your pentosin fluid mate !
    I'm pretty sure it's not even part of scheduled maintenance, but when you look at the color comparison between the old and new fluid I have posted, for sure the old fluid has lost some of its properties .. maybe allowing creation of air bubbles when the fluid temp is rising on hard driving. :confused:


    Good info, didn't saw this clutch test in DIS ! I will check this asap, I hope it will be fine :D

    Yes, definitely, when the kickdown is pressed on full throttle it makes a difference in shifting speed and power output. Also it's simply because when pressing the kickdown, you will have a little more accelerator pedal travel and it will open further the ITB.
    I don't know if you remember it but we had a conversation about TPS value in another thread, when I was trying to solve a power problem. I had only 82% opening with DIS on full throttle(with kickdown) before, then I adjusted the ITB stopping screw and accelerator cable, and I managed to reach your values now .. the car is considerable faster and it was confirmed on the dyno a few weeks ago :)


    You didn't noticed the rev matching ? :eek:
    Mine does always a rev match when I downshift in sport mode, you can really hear it ! It makes the down shift really smooth, and with the supersprint race it makes for sure a nice sound :D
    Maybe because of the supersprint loudness I can hear it more that you haha


    We can try your kickdown hack with a little ziptie to hold the kickdown always pressed. I'm tempted to try !
    But I think the shifting speed depends more on the accelerator pedal position than the kickdown, so I'm not sure of the result.
    If with this hack we are in maximal shifting speed all the time, even on slow driving, that would be a HUGE upgrade :eek: :D

    I have noticed the other day that my rear tyres are spinning a little on 1st to 2nd gear change on full throttle, so yeah SMG 1 performs not too bad.
    If the weather is nice, I'm going to spa-francorchamps track in a few weeks. I'm really excited to see how it performs on track. Not sure the gearbox is really adapted to this, but anyway I will drive it "gently" :p
     
  4. 15 Mar 2016 at 11:56 AM #4
    MParallel

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    Funny thing is, in the gearbox in DIS I reach 100% with pedal fully depressed (with kickdown, without it, you're at 96%)

    But in the DME section, and I actuate the throttle by hand, I only get to 91%. So not sure what is going on.

    I doubt anyone would ever fiddle with the stopscrew. Unless the ITB's are no longer synched on their axes. IIRC the stopscrew is set at the factory and it says do not touch it.

    I can imagine the kickdown map is a function of both kickdown pressed + throttle floored. But maybe the system isn't so clever and it will just go into the fastmap.

    But if it also alters injection/timing it could maybe run weird. Although it should still look at the MAF and TPS for that.

    Who knows!

    I've been to the Nurburgring more than once with the M3 and it's excellent on track.
     
  5. 15 Mar 2016 at 3:08 PM #5
    thvdevel

    thvdevel Rocking a new hat

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    I reckon that the reading is funny. Because when I was adjusting the ITB and throttle cable, I have used DIS too to check the value of "Angle-throttle valve" in gearbox live values.

    I had removed my airbox to properly set the stopping-screw, i.e. the ITB bracket was touching the screw when the valves had done a 90° rotation in their housings. By eye, you could see that this was the correct opening. I have also taken approx measurement to verify that I had the same trends like in TIS document. (distance between the valve and top/bottom of housing)

    Then I have looked what reading I had in DIS when the ITB bracket was touching the stopping-screw, and I had only 90% ! (bottom right)

    [​IMG]


    I have noticed that if I want to get close to the 100% reading in DIS, I need to screw the stopping-screw further so I can open the ITB more.
    But then the valves rotation is way past the correct 90° degree opening, and by opening them too much you reduce airflow.

    If we assume that the valve looks like this in the housing after a 90° rotation : -- , then if you try to rotate it even more you will get this : / (with exageration)


    So I know that in my case 90% reading in DIS was the correct ITB opening, not more.


    BUT then I have driven my car for 1h, and checked again DIS reading .. and without touching anything, I was close to 98% .. :eek: :roflmao:


    So .. In summary, I think that DIS regarding this "Angle-throttle valve" is not uber precise. On cold engine I had ~90% and ~98% on hot engine. I guess with the heat, the TPS reading can slightly change.

    Anyway, It's better to remove the airbox like me, and check by measurement that the ITB are correctly opened to be sure and don't rely too much on the software. :)
     
    Last edited: Mar 15, 2016
  6. 15 Mar 2016 at 3:43 PM #6
    MParallel

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    Has yes that was it. The value in INPA was 91% on mine. I thought maybe the TPS was faulty, but I do get 100% in DIS.

    Now there is also the pedal travel sensor we have. Maybe the 100% is the value of the throttle actuator!? (to make things even more complex...)

    TIS also shows that regardless of the ITB lever hitting the stopscrew, the butterflies can be adjusted on the shaft.

    But I really doubt my 52k mile car has these off. I can see how much the butterfly axle rotates when I adjust the other axle through the lever and by eye this is 90 degrees. So must be fine.

    ps, I think it's much easier if you want to test the kickdown map, but simply unplugging the connector and bridge the contacts than zipping it down.

    Would be nice to a side-by-side to see if one's SMG box shifts differently. I have two friends with both also SMG cabrio's one's been in a big project for like 3 years and the other one should hit the road again soon.

    That last guy showed me the launch control. He has a 5 puck race clutch. Damnit, that thing flew.
     
  7. 29 Sep 2016 at 1:06 PM #7
    kyrix1st

    kyrix1st Wearing official robes

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    How do you use the DIS? My 20-16pin does not let me use.
     
  8. 29 Sep 2016 at 8:42 PM #8
    MParallel

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    Don't think this is the appropriate topic to talk about DIS, whole forums sections exists about DIS and coding.

    I can't tell why yours won't let you. I just hook it up and connect.

    There are tons of cables and port combinations.
     

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