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  • Electric power steering pumps.

    Just mulling it over...

    I know this has been discussed before, has anybody done it? is there any drawbacks with regards extra load on the alternator, or is there any issues with over assistance at speed, does it need variable voltage ? etc.

    Been looking at some options, a A class merc pump has been mentioned, but what about the BMW Mini version, (keeps it in the family...)

    What about wiring, whats the best way? could be 60-70amps at full lock, whats the best way of dealing with this, circuit breaker, solinoids, relay etc.

    How about mounting, suitable places????

    could it be an advantage on track if you switched it off ?

  • #2
    all people that i know use the MB A-class one in their race cars
    e30 M3s and e46 M3s
    maybe i am as well in the future

    Markus

    http://www.bmwm3shop.de

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    • #3
      I have fitted a few of the BMW motorsport pumps to a couple of race cars. Quite expensive(NZ$2000 for the last one) but a nice bit of gear.It is the same part fitted to the E36 and E46 touring cars. It is made by VDO, and is a complete self contained unit (pump, reservoir etc.) It only has 3 wires to hook up, ground, +12v, and alternator. Alternator wire goes to warning light terminal on back of alt. so that it only runs when the engine is.Then it is just a feed hose to the rack and a return. I can't remember the current draw, but I think it was around 30amps or so, and I didn't bother with a circuit breaker, although do so at your own risk! The operation is superb, and the momentary extra drag on the alternator, as the pump loads up, would certainly be less than the mechanical pump, and probably when it doesn't matter so much, such as slowing for a corner. I wouldn't be at all surprised if it is an OEM part, it does look like a mass production piece and may be had for less money from somewhere else perhaps? What brand is the A class pump?
      Last edited by conrod; 02-16-2006, 07:30 AM.
      sigpic

      www.m3motorsport.co.nz

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      • #4
        Marcus, do you know how the A Class pump wires in? is like above with just 3 wires?

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        • #5
          Re: Electric power steering pumps.

          Originally posted by UK215M3
          Just mulling it over...

          I know this has been discussed before, has anybody done it? is there any drawbacks with regards extra load on the alternator, or is there any issues with over assistance at speed, does it need variable voltage ? etc.

          Been looking at some options, a A class merc pump has been mentioned, but what about the BMW Mini version, (keeps it in the family...)

          What about wiring, whats the best way? could be 60-70amps at full lock, whats the best way of dealing with this, circuit breaker, solinoids, relay etc.

          How about mounting, suitable places????

          could it be an advantage on track if you switched it off ?
          There are not many switches that can handle 60-70 Amps. If the power draw is that large, and you want to switch it in and out, then you should use a relay.

          A fuse or breaker would be very wise.

          You refer to an electric power steering pump. There are also cars with electric power steering. The assist is electro-mechanical, not hydraulic. One nice feature of these is that they use strain gauges for the feedback loop, and you can easily play with the voltages to change the assist level.

          I used to think you could do the same with a hydraulic system by lowering the fluid pressure, but I'm not positive about that. From what I can tell from reading other's experiences, slowing down the pump does not necessarily reduce the assist level. I've not tried it myself.

          F1 cars use electric power steering, not sure about Sports Prototypes and Touring Cars these days, though they do seem to all use power steering of some type. Not many manual steering systems in racing these days...

          Gustave

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          • #6
            In the case of the motorsport pump, you would switch it on and off by running the alternator wire through a toggle switch, and leaving the heavy wires permanently connected. I think most electro-hydraulic pumps are wired in a similar fashion,power wires permanently connected, and lighter switching wires connected to whatever to turn the pump on and off. Some cars have speed sensitive power steering (the new 7 series?) and these vary the output pressure, according to the input signal, usually from the speedo. For simplicities sake, I would find a constant pressure pump for your use, I only have experience with the BMW motorsport pump, and it was a good setup, steering still nicely weighted, witha good amount of assist. I have seen a few electro-mechanical setups, very nice and compact, but would be an absolute mission to retro fit one into your car, as it is part of a complete steering column, so enough said I think.
            sigpic

            www.m3motorsport.co.nz

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            • #7
              I have an electric hydraulic pump fitted to my car , I have fitted it under the co-drivers foot rest inside the car , it is off a Citreon Saxo / Peugeot 106 gti over here in the uk , I have 2 aircraft trip fuses of 30amps each feeding it , it seems ok so far but I havent really driven the car properly , will be doing an auto X on the weekend so will see how I get on with it , the trouble I'm having is finding a quick rack , I would like to get something like a 2:5 turn lock to lock , after reading advise somewhere I bought an E36 3:0 M3 rack being told it was the quickest off the shelf rack , only to find out its about the slowest , been told the Z3 is the one to go for but would like one a bit quicker , if it means going to a non power rack I'll do that and fit an electric column.

              Cheers Ian

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              • #8
                Hi Ian

                I have aload of e21 quick racks, that i have been told are fittable, the other is an upside down lhd talbot sunbeam rack. I will be getting a batch of e30 racks made buti need to shift the dozen e21 kits i have first.

                The alternative is too use a steering quickner basicaly, a small in line gear box which ups the ratio.

                Jason

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                • #9
                  I am now at the third company in the UK for a Kwik rack that is non power assisted.

                  Problem is that the BMW ZF Manual Rack has a 'V' shapped drive, which all the companies are not set up for.

                  Most of the Power Racks and other manufactures Manual racks are semi circular shapped drives, but not the BMW Manual ZF.

                  So then, while that is being sorted, maybe they can do it maybe they can not, it will be 2.2 lock to lock if completed, I went and obtained a Z3 Power Rack, 2.7 lock to lock, and was going to couple that to a Merc A electric power steering pump.

                  This works, but be careful as the Merc pumps are with 2 wires and 3 wires, and to make a relay work you will most certainly require a 3 wire Merc pump from a A class.

                  Secondhand they are almost unobtainable in UK, as they sit at the front in the A Class and are prone to damage.

                  Best price new was 266.00 plus Vat from a dealer.

                  I posted a while ago about the Upside down Talbot Sunbeam Rack, but have pursued the possible 'manual' option or 'Z3' assisted.

                  Regards,


                  The Gorilla.

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                  • #10
                    Gorilla - did you find anywhere that does a power quick rack ?

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                    • #11
                      Ian,

                      In short No.

                      One said they could, but when it came down to the costs of re-tooling, well you get the picture.

                      Regards,

                      The Gorilla.

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                      • #12
                        Ian, do you happen to know the relative part numbers for the 3 wire pump?

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                        • #13
                          Mine is a 2 wire pump , just a live and neutral , with the live on 2 fuses but joined as one to the pump , I didnt wire them myself , it was all done with the loom

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                          • #14
                            Originally posted by conrod
                            I have seen a few electro-mechanical setups, very nice and compact, but would be an absolute mission to retro fit one into your car, as it is part of a complete steering column, so enough said I think.
                            It would take a bit of work yes, I agree.

                            The tough part is that an EPS (Electric Power Steering) system is ECU controlled. So you need to get the ECU, and then find out what signals it has to have and which it can live without. For instance if it won't work without a digital vehicle speed input, then you're out of luck. But you might be able to fool the ECU with some type of simulated input. It would take some playing around.

                            I have reservations about the "steering feel" that would be provided by the EPS racks that we would be able to get access to, usually from Japanese commuter cars. I really don't know if any German cars, let alone BMW's are using EPS. The steering feel issue may be part of the reason if they are not.

                            Running a hybrid system, with a hydraulic rack and just an electric pump is still attractive, just to get rid of the pump on the engine. And you still get the same steering feel as you've always had, as that is mostly a function of the rack. The pump just provides pressurized fluid (more than enough pressure, the excess is blown by).

                            Gustave

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                            • #15
                              I run the Mini system on my E36 race car, and would be happy to sell full kits to people for BMW use. The current draw is indeed up to 70 amps, and I include a 100 amp fuse as installed in the MINI. I've sold several kits. Incidentally, the reason most of these system are attached to the Alt charge light is so that they can revert to manual in the event that the alternator fails. In that case, you will not drain the battery, and the engine/car will still run, albeit with a manual steering system. This was pretty funny for me personally when I moved my alternator to the rear seat area, ran it off the drive shaft, and installed a drysump pump where the alternator had run before. It took several brake zones of "whoops??? no steering?" before I realized that my pulley combination was saving so many revs on the alternator that the built in computer in the MINI pump was interepreting the situation as "dead alternator" every time I slowed down enough to brake, and go through a turn. Devastingly funny as the system had worked fine while the alt was on the engine. Now of course, the PS system is on a toggle switch on the dash.
                              91 Z1, 94 M-Technic S54, 95 M3 LTW S54 almost in, E39 540 6 MT (32K new engine)

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