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Thread: Experimental servotronic module ?

  1. #1
    Join Date
    Mar 2020
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    Le Mans, France
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    1991 850i individual

    Experimental servotronic module ?

    Hi

    While chasing for hig power consumption during IDLE phase (~400mA instead of 40-50mA),
    i started to check every module / connection in the car.

    I found this black box plugged in place of the servotronic module (white one).
    PXL_20230311_105914149.jpg

    Inside the black module, 2 PCBs :

    PXL_20220319_155250603.jpg

    the "BMW servotronic" board

    PXL_20220319_155348169.jpg

    and the "prozessorboard"
    PXL_20220319_155408050.jpg

    Does anybody have already seen this kind of experimental servotronic module ?

    Thanks
    Last edited by pchotard; 03-12-2023 at 04:20 PM.
    1991 850i (Servotronic - EDC - ASC-T - AHK - Alpina rims)

  2. #2
    Join Date
    Feb 2010
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    Hampshire UK
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    99 840ci Sport Indv
    Brilliant! I would suggest Hyper if it were not for the 'PROZESSORBOARD' marking which probably indicates some Russian involvement!
    Last edited by Timm; 03-11-2023 at 05:38 PM.
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


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  3. #3
    Join Date
    Aug 2007
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    San Ramon, CA
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    850Ci, M5, Model-S P85D
    That looks like a lot of work for a 1-Off prototype.
    Your 8 is in France!! wow... French Connection upgrade!!
    Based on the oldest date codes on the chips it was built in the early to mid 1990's, or at lease after 1991 from the date on the EPROM.
    So it has been a while..

    I anticipate your 8 isn't the only one that was in on the servotronic steering system upgrade effort.
    However, discovering who and what performance improvement was desired and how effective was this new module, will be the question.
    I anticipate this module could have also been installed in E32 and E34 with servotronic steering, so that would widen the search.
    Cheers,

  4. #4
    Join Date
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    '97 840CI
    OK, my turn to guess.

    Not exactly something that would come off an assembly line.
    Assuming its not a production unit, yet has the Siemens brand, that points to either engineering development or field service diagnostic equipment, with company people accidentally leaving it behind.
    Or perhaps it was a deliberate swap by a genuine BMW shop, just to get the vehicle back on line.
    ***
    I'm actually in Munich next month.
    Gives me a reason to stop by and snoop around.

  5. #5
    Join Date
    Jun 2008
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    SF Bay Area
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    Supercharged 850ci
    Wow, never seen anything like this.... and I've seen aloooot of 8's

  6. #6
    Join Date
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    850Ci, M5, Model-S P85D
    The Siemens part PN: 61361393412 is the BMW production Servotronic relay that is a retrofit/upgrade for the OE Servotronics module
    I like Timm's assumption!!
    It's the Russian's, the Russian's did it. A poor reference to Ronin!!

    My wonderment is why would you put that much effort into Servotronic Steering, i.e., speed sensitive 2-stage power steering.
    I

    The PCB plate through holes manufacturing imply the boards were professionally done, CAD design to PCB manufacturing.
    Certainly, companies offering that service emerged with FTP available, but the production cost would make it a small quantity build at a minimum.

    The real issue is being, it was built in the early 1990's making it very early if not pre-Internet Era effort.
    The real NetScape Internet Web search activities didn't occur until the mid-1990's with Win95.
    Also, file storage came at a premium back then, so it is unlikely the project design information made it into the Mass-Storage Search-Engine Internet Era.

  7. #7
    Join Date
    Mar 2020
    Location
    Le Mans, France
    Posts
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    My Cars
    1991 850i individual
    My 8 serie has been built beginning of 1991 (february to be exact).

    This car has also another particularity, it is the fourth 8 serie equipped with AHK and there is an
    additionnal 7-pin round connector in the engine bay which was not documented in the ETM and related to AHK.
    see this thread for more details

    So has this car been used for experimental test / development ? It embeds all nice 8 serie feature as EDC / ASC+T/ AHK and servotronic.
    Reading this forum since a while, it shows that this feature combination is rare for a 1991 850i and probably one of the first with this combo.
    Last edited by pchotard; 03-12-2023 at 05:08 PM.
    1991 850i (Servotronic - EDC - ASC-T - AHK - Alpina rims)

  8. #8
    Join Date
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    99 840ci Sport Indv
    Although Servotronic was not available in the US in 1991 - it was in Europe and appears on the 1991 circuit diagram, as was ASC+T and EDC - the AHK was used in the promotional video for the 8-series as it was released
    Timm..2007 E64 650i Individual Sport..1999 E31 840ci Individual Sport..ex owner of 2000 E38 740..1999 E38 740i V8 M62..1998 E38 735i V8..1993 E32 730i V8..1988 E28 518i


    My BMW Repair YouTube Channel
    My Current 840ci Sport Individual
    My Current 650ci Sport Individual
    My E31 Repair and Information Website
    My E38 Repair and Information Website
    My E63/E64 Repair and Information Website

    Chase - Heroes to a generation

  9. #9
    Join Date
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    '97 840CI
    Quote Originally Posted by Timm View Post
    ...would suggest Hyper...
    Thanks for the hat tip.

    *** OT alert !!
    Literally current project: A relay board powering a PTC heater unit retrofitted into the duct work of my van for "instant on" defrost.
    This board actually was originated to bypass the failed fuel pump relay on member Alex840's Cooper coupe.
    Btw my only board not sporting a Prozzesor.

    Hyperdrive GPR - General Purpose Relay board
    Two relays, each good for 35A.


    PTC heater, retrofitted into hvac duct, for "instant on" defrost.
    Controlled by the relay board.


    Same relay board attached to Alex840's Cooper control box, to bypass failed factory design for fuel pump power.

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