Dynamic Brake Control (DBC)

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 669

  Z3 roadster 2.2i

Dynamic Brake Control (DBC)

Post by motco » Mon 26 Feb, 2018 09:48

I have a very late Z3 2.2i Sport built in the last week of production in summer 2002. Occasionally I have encountered an awkward behaviour by the braking system and that is that when I have brake abruptly, as one might on a country lane if a car appears coming the other way carrying a bit of excess speed, the brakes have seemingly self-applied with ABS activated if I brake briskly but not excessively hard. It's as if it has taken over the brakes and stood on the pedal. Some BMW models have DBC which behaves just like this so I wondered whether the last iteration of the Z3 might have it too. Some research suggest that it may well have it. Does anyone know please, and also can it be switched off? Thanks.

mrscalex
Joined: Fri 13 Mar, 2015 09:14
Posts: 869

  Z3 roadster 1.9

Re: Dynamic Brake Control (DBC)

Post by mrscalex » Mon 26 Feb, 2018 11:25

You quite possibly mean DSC - Dynamic Stability Control.

Have a look on the passenger side of the engine bay. If you have a bunch of pipes going into a silver box with a black plastic module on top you have ASC.

If there's nothing there and a similar arrangement is contained within the brake servo area (back of the driver's side - look deep down into the area) then you have DSC.

I would probably expect you to have DSC. I don't know the ins and outs of how it works. I'd try and find a handbook PDF online and I expect it will explain it in there.
ImageImage
2001 Z3 2.2 Topaz Blue (Trudy) - Keeper rebuilt from a write-off
2002 Z3 2.2 Titan Silver (Cookies) - Keeper rebuilt having been bought with a seized engine
2002 Z3 3.0 Sapphire Black (Peanut) - Keeper awaiting rebuilding having been bought as an abandoned project
Plus Willy, Kodak & Maycee - All 2.2 Sport projects. Yes, 6 is a lot of Z3s :)
Always happy to try and help with spares :)

Bumpa
Joined: Fri 23 Jun, 2017 21:31
Posts: 45

  Z3 roadster 2.2i

Re: Dynamic Brake Control (DBC)

Post by Bumpa » Mon 26 Feb, 2018 14:20

My 2002 Z3 2.2 Sport has DSC and it has caused me quite a lot of bother. The problem with my car, which might be the same for yours, was rain water ingress soaking under the carpets. Just in front of the passenger seat (RHD car), bolted to the floor are two sensor modules to assess lateral acceleration and yaw. In theory, if these sensors detect unusual sideways movement they can apply various brakes to attempt to stabilise the car. Lord knows if it would work, but I would rather be without it. I have noticed when pressing on round twisty country roads that you can get a flash of the DSC warning light as the system thinks there is a little too much sporty driving going on. Goodness, you mustn't drive a sports car in a sporting manner!

On my car these sensors were having a nice swim in pints of water and gave errors and warning lights. The faulty lateral acceleration sensor was replaced under the warranty I had with the car, but it took weeks of effort to stop the rain getting in and drying out the foam under the carpet. Oh, and the new sensor had to be calibrated by the computer thingy in the garage of my local independent.

I hesitated about buying this car because I knew how complex the electronic systems are. And what do you know, within the first 4 months of ownership a complex electronic problem occured. I should stick to my 40 year old classics. No electronics at all! :D

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 669

  Z3 roadster 2.2i

Re: Dynamic Brake Control (DBC)

Post by motco » Mon 26 Feb, 2018 16:35

Mrscalex, I do mean DBC not DSC and further research tells me that cars with DSC also have DBC, but those with ASC do not. Dynamic brake control assesses the apparent urgency of a braking event and if deemed a 'panic' brake it will apply full brake effort until you come off the pedal completely. Having had mine operate (I now am sure that is what happened) I would really rather not have it. I do not need some girly over-servoed braking when all I might be doing is driving in a 'spirited' manner than you very much!

Bumpa, that brings me to your comments about DSC. Below is a post I made in January 2016 - it is self explanatory.
I was travelling clockwise on M25 near Reigate on New Year's Day at mid to late afternoon in my Z3 2.2 Sport. It was getting dark and the traffic was moderate (light by M25 standards) with very few lorries but lots of cars. I was on cruise at a GPS 70 mph in lane 3 of 4. On my right and to the rear was a large white car (Audi I think) gaining on me by about five to ten mph, and on my left in lane two another car (unknown make) travelling some five to ten mph slower than I was. So far, so normal on M25 with all its gantry cameras causing little speed differential across the outmost three lanes. There was nothing ahead of the lane two car for some distance and indeed not a lot immediately ahead of me because the braking distance at that speed dictates a good headway to the car ahead. As I drew alongside the car to my left he suddenly and unneccessarily started to change lane towards my nearside. This was no lane drift; this was a deliberate lane-change manoeuvre and had I not taken evasive action he would have barged me across to lane four where the Audi was now approaching alongside. Instinctively I swung the wheel quickly through about 90 degrees right and then instantly back sufficiently to regain the course in the lane in order to move the car at least half a vehicle's width towards, but not into the path of, the car in lane four. He (the Audi) must have lost control of his bowels when he saw what was apparently a small two-seater diving across his path and then, equally suddenly stopping the swerve! Doing this in some (most) cars on a damp concrete road surface at 70mph would almost certainly have resulted in a total loss of directional control, but in the Z, thanks to DSC, it did exactly what was asked of it with no more than a couple of flashes of the yellow DSC light on the dash! I am so glad I took the Z yesterday and not my Jag X Type - that has traction control and ABS but no stability control. What's more it's a bit of a heavy lump and would have been unlikely to be as nimble as the Z anyway.

Over the years I have driven in excess of a million miles and can honestly say that I have never had such a stupid driver threaten my safety.

mrscalex
Joined: Fri 13 Mar, 2015 09:14
Posts: 869

  Z3 roadster 1.9

Re: Dynamic Brake Control (DBC)

Post by mrscalex » Mon 26 Feb, 2018 18:56

DBC is one aspect of DSC. The build option is whether it has the DSC system or not and hence the DBC as a component.

If you PM me with your email address I will send you a BMW document that explains the components of the system, the sensors/inputs and how it all works.
ImageImage
2001 Z3 2.2 Topaz Blue (Trudy) - Keeper rebuilt from a write-off
2002 Z3 2.2 Titan Silver (Cookies) - Keeper rebuilt having been bought with a seized engine
2002 Z3 3.0 Sapphire Black (Peanut) - Keeper awaiting rebuilding having been bought as an abandoned project
Plus Willy, Kodak & Maycee - All 2.2 Sport projects. Yes, 6 is a lot of Z3s :)
Always happy to try and help with spares :)

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 669

  Z3 roadster 2.2i

Re: Dynamic Brake Control (DBC)

Post by motco » Mon 26 Feb, 2018 20:23

PM sent, thanks

Brian4
Joined: Mon 19 Dec, 2011 19:02
Posts: 539

  Z3 roadster 3.0i
Location: Hinckley

Re: Dynamic Brake Control (DBC)

Post by Brian4 » Tue 27 Feb, 2018 18:47

The later z3 have a slightly different DSC to the earlier ones.
Brian
3.0I Topaz Blue


2000 E36/7 Z3 3.0i
2016 F31 335d
2015 F21 118i

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motco
Joined: Tue 18 Aug, 2009 19:12
Posts: 669

  Z3 roadster 2.2i

Re: Dynamic Brake Control (DBC)

Post by motco » Tue 27 Feb, 2018 19:26

Mine was built in w/c 23 June 2002 (26th if memory serves) and production ended on the 28th - pretty late then! In what way 'different' Brian4?

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