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Thread: Retaining braking component of the ASC system only

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    Retaining braking component of the ASC system only

    1/1995 540i6 with an S62 swap. Running the S62 DME.

    I'm trying to sort out my ASC--in a nutshell, I'd like to have as much of it as possible. This car is driven year-round, and we do get snow here. The LSD is not enough.

    Of course the throttle plate is gone, so there cannot be any throttle, er, throttling. That being said, I'd like to retain the wheel-braking component of the ASC system. All my wheel hardware is the same, I still have the ABS computer. Long shot, I know; Is it possible to reprogram it, perhaps, to only effect the braking part of the ASC?

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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    You're driving an S62 E34 during salt season? For shame.

    LSD makes it harder - gets you moving but not necessarily in the direction you want to go. My 544iT was a lot less of a handful with an open diff than with an LSD.

    I deleted my ASC to retain ABS only, but you're talking about retaining the rear braking function? I'd avise against it; the secondary throttle and rear braking are designed to work together, and you may get poor results with an S62 allowed to do its thing while the rear brakes are doing their own thing at the same time. If you want to try, keep all the ASC hardware including the secondary throttle plate with its own throttle position sensor. Mount them securely somewhere. The system pulls a throttle cable and checks for results via the secondary TPS. If it also checks for results from the ECU, you're out of luck, but it may not do that.

    For that matter... ABS and ASC both talk to the ECU. Did you wire up the S62 ECU to keep those signal wires? Does ABS work? Its warning light is separate from the ASC's light; are either on?
    Last edited by moroza; 07-06-2018 at 09:48 PM.

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    Thanks for the reply. I drive all my cars year-round. I rustproof and clean them obsessively, and it's worked pretty well for me. Truth be told, there's no point in having a nice car if you only drive it for six months of the year.

    My ASC light is on. Insofar as I can tell, the S62 ECU does jive with the ABS (no problem with that system, no ABS warning light but I have not yet tested it). Your point about the braking while the engine still delivers power is well taken--but as I understand, the '95 system had a 'development mode' that allowed just that. Truth be told, the reason I want the rear wheel braking is specifically for winter, where black ice patches can spin a car very easily (been there, done that) with no warning. It has saved my bacon in an E39 a time or two.

    I guess the question becomes, where does the ASC get its data? And, perhaps, is there a way to program it to remain in that 'development mode' or something akin to it where it doesn't look for a secondary throttle?

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    moroza is offline MORΩN ΛABIA BMW CCA Member
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    I hear you on the "meant to be driven" concept, but there's also the concept of "right tool for the job (road conditions, in this case)". Anyway...

    Where'd you read about this "development mode"?

    Like I said, it gets at least some of its data from the secondary TPS, in addition to the wheel speed sensors. It may also get data from the ECU, or it may not. If it doesn't, a dummy throttle setup should fool it - it'll still close the throttle but that won't do anything to the engine if mounted elsewhere, and it'll still work the brakes like normal.
    Last edited by moroza; 07-07-2018 at 06:38 PM.

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    When I did my swap from the m60 to m30 I disconnected the ASC actuator and found out I still had the ABS part working just fine.
    demet

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    Quote Originally Posted by demetk View Post
    When I did my swap from the m60 to m30 I disconnected the ASC actuator and found out I still had the ABS part working just fine.
    Wish I'd known that 9 years ago, before splicing an entire ABS harness to keep ABS but get rid of ASC. But OP wants to keep not only ABS but also the automatic individual rear braking that's one part of what ASC does, while disabling engine throttling, the other part.

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    I don't understand how you can have ABS controlling wheel lockup in a sudden stop and at the same time have the rear brakes controlled by ASC. How is that done and why would you want it?
    demet

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    Simply put, the ABS releases brakes (as needed) when the brake pedal is pressed. ASC applies them (as needed) when the brake isn't pressed. The ASC unit and ECU live on the ABS unit (whose ECU is in the ebox). I suspect I need to bypass something in the ASC ECU.

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    FWIW dedicated snow tires and LSD have served me well in Chicago's winters. I find the ASC too intrusive on the wife's E39 and shut it off, she prefers it as any lateral motion scares her. A little controlled wheel spin never hurt anybody.
    Granted, you have more ponies but the same principles apply.

    If you can leave two black stripes from the exit of one corner to the braking zone of the next, you have enough horsepower. - Mark Donohue

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    Quote Originally Posted by ross1 View Post
    FWIW dedicated snow tires and LSD have served me well in Chicago's winters. I find the ASC too intrusive on the wife's E39 and shut it off, she prefers it as any lateral motion scares her. A little controlled wheel spin never hurt anybody.
    Granted, you have more ponies but the same principles apply.
    Fair enough. I guess the next question would be, how to eliminate all the warnings? (I can remove the bulb, but what about the ASC error message on the OBC?)

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    Quote Originally Posted by tantumaude View Post
    Fair enough. I guess the next question would be, how to eliminate all the warnings? (I can remove the bulb, but what about the ASC error message on the OBC?)
    Can't you just short the pin out on the Check Control Module?

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    Quote Originally Posted by XAlt View Post
    Can't you just short the pin out on the Check Control Module?
    Honestly, I don't know.

    (hoping for someone knowledgeable to chime in)

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    Will any part of ASC work if any other part is throwing error signals? If not, you may as well rewire to ABS like I did.

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    I'm confused. I see what you're trying to do though. I thought the later ASC systems only had the second throttle body for the ASC system. When I removed the ASC+t system from my 94 530i, it had that secondary pump that applied the rear brakes if the ABS detected wheel spin. That was a very early (4/93) car though.

    95 540i6 M Sport - 95 525it S52/OBD2 - 433k E36 328i5 - X5D that hit a pothole - IG: @justinmurray95

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    No, mine definitely has the rear wheel braking. I've noticed it working a couple of times before the swap.

    I think the 1995 system was different. Pre-95 had regular ASC (throttle only) or ASC+T (both systems). 95, as I understand it, has the ASC+T, but renamed ASC and simplified.

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