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Hydraulic to Vaccum servo conversion

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  • I spoke with LhdKid about this issue and he suggested to make an excentric pedal adapter
    to maintain the same piston travel as before...because installing the pin higher on the pedal will shorten the piston travel..and i dont want this.
    Last edited by Pirvu Eugen; 25th March 2017, 12:07.

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    • I gave up on the twin servos after having so many leak in my urs4. Using an a6 single vacuum unit now.

      Sent from my LG-H955 using Tapatalk

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      • Off... yes... the dual diaphragm one is more complicated and prone to failure as the single one..
        Thank you Des for feedback!
        Last edited by Pirvu Eugen; 26th March 2017, 07:53.

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        • Are the twin ones so prone to failure when they are in their original habitat? I mean, does an S8 or RS6 suffer a lot from servo failure, or is it just when they are messed with?
          Honda CBR 1100XX Blackbird Turbo....undergoing major changes.....
          S2 Coupe... bit easier off the line...
          '03 ZX12-R daily hack.... lots of nice bolt ons...

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          • Dont think so... i searched and nothing came up. Not as the new mercedes ones.
            I think that poppet valve rubber thing is not working ok with high rod angles.

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            • Originally posted by Pirvu Eugen View Post
              Dont think so... i searched and nothing came up. Not as the new mercedes ones.
              I think that poppet valve rubber thing is not working ok with high rod angles.
              So, the answer really is to replace the standard fork which connects to the pedal with an eccentric one which can move the pivot point over the required amount to keep the pushrod going straight into the servo unit.

              Looks like its between 5 and 10mm, will measure more accurately next week and get something made.

              I wonder if just doing this will work, without having to swap the booster out.........
              Honda CBR 1100XX Blackbird Turbo....undergoing major changes.....
              S2 Coupe... bit easier off the line...
              '03 ZX12-R daily hack.... lots of nice bolt ons...

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              • I've just measured the coupe... the deflection of the rod from straight is around 1mm

                I don't think this issue affects the conversion on an S2 for example.....
                Honda CBR 1100XX Blackbird Turbo....undergoing major changes.....
                S2 Coupe... bit easier off the line...
                '03 ZX12-R daily hack.... lots of nice bolt ons...

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                • I measured now at my 200 and the rod deflection is 10mm.
                  This explains why this failure happens only in C3..C4 chassis with these servos.

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                  • This thread is a mess!!! The OP I assume, as its not stated, is converting a LHD car?? Also, multiple people taking about fitting different servos on LHD and RHD non-S2 models!!!!

                    Can someone give a parts list required to convert a RHD S2 car to vacuum servo??

                    I am assuming that servo 8a2612105a is the required part and then there is the mounting bracket, is that or not required?
                    sigpic
                    Tom C - www.rcmr.co.uk
                    Audi UR Quattro
                    Audi 100 C3 2.0 5 cyl 115ps
                    Audi S2 - 07k engine project aiming for 800ps
                    Audi B5 RS4 645ps 911nm

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                    • Originally posted by audiman View Post
                      This thread is a mess!!! The OP I assume, as its not stated, is converting a LHD car?? Also, multiple people taking about fitting different servos on LHD and RHD non-S2 models!!!!

                      Can someone give a parts list required to convert a RHD S2 car to vacuum servo??

                      I am assuming that servo 8a2612105a is the required part and then there is the mounting bracket, is that or not required?
                      When I posted this I did use the document from the US, so an LHD car which you can see from the attached pdf. I didn't follow what others wrote about the RHD process, sorry

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                      • B3 no, B4 yes, I think.

                        When I got mine for my B3 CQ20V I asked that the servo came with the bracket and any pipework to save hassle, however I didn't need the bracket, as my Coupe had one already fitted

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                        • Originally posted by Horsty View Post
                          Hi Guys,

                          sometime last year i fitted the a8 d2 brake booster and master brake cylinder in my 7A quattro coupe and i thought it might be interesting for one or the other...

                          7x8 inch brake booster combined with the 25,4mm master brake cylinder.
                          the other option would be the 26,9mm i guess. but that would be overkill.


                          adapter plate needs to be fabricated. otherwise the brake booster will be leaky.




                          a6 v6 hydraulic steering pump. quite the same pump used for a long time at audi.
                          a4 b5/b6 or B4 v6 is also the same. bolt on directly to the 7A bracket.


                          brake booster without grommet. you see these tubes coming out of the brake booster for the bolts.
                          the "tubes" are not the same level as the brake booster surface. thats the reason for the adapter plate i made.


                          adapter plate alignment.


                          difference between the hydraulic spacer (short one) and the vacuum spacer (long one).


                          adapter rod and the grommet mounted.


                          adapter plate, vacuum spacer, adapter rod and that kind of fork mounted.


                          this adapter needs to be fabricated to increase the rod length:


                          ready for installation:
                          You can not see the photos, could you upload them again? I'm interested in making the change.

                          REGARDS

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