Bottom end advice

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  • 20Vcqdriver
    S2Forum Maniac
    • Jun 2007
    • 829
    • Country: United Kingdom

    #1

    Bottom end advice

    Well I am expecting to start gradually building up a new 3B bottom end for my Cq over the next few months (last part of the car not overhauled) and intend to build it to withstand the proposed 380bhp and subsequent torque. Having spent a lot of time searching for whats best and not getting a 100% answer I thought it would be easier to just ask what are the best components to use for this. I.E. type, spec and company to buy from etc. There seem to be plenty of rod options but sizes seem to vary by a mm or so.
    Looking to rebore block and use appropriate oversize pistons if these are available and hope to be still able to use the standard metal ADU headgasket with it. Thanks.
    1986 Coupe q - 2281cc 3B, chargecooler, 2.75" exh & downpipe, ported head, water injection, CGR box, modified MD357 turbo, 440cc injectors, high power coil.
    2004 A4 2.5TDi convertible, re-mapped to 180bhp
    2011 A5 sportback 3TDi-Backbox delete, remap
  • Error404
    Super Moderator
    • Mar 2007
    • 19789
    • Country: United Kingdom

    #2
    You don't need to over-bore and have new pistons unless the bores are out of spec, you should be fine with a rehone and new rings maybe?
    I'm doing the same are you with a 3B bottom end really, and just looking at stronger rods and uprated bearings
    Panthero Coupé quattro 20vt
    Indigo ABY coupé
    Imola B6 S4 Avant

    Comment

    • Flat on my back
      S2Forum Fiend
      • Jan 2007
      • 2449
      • Country: United Kingdom

      #3
      .

      3 thou is the top wear limit then you'll need a re-bore, believe there is a Wossner set that starts at 81mm.

      My donor 7A block was measured at 1 thou wear on the worst bore, so get this checked first.
      Carlos.

      On the look out for less bits for my s2 saloon project. Now supporting myself by shooting for my food. www.airgunforum.co.uk

      Comment

      • 20Vcqdriver
        S2Forum Maniac
        • Jun 2007
        • 829
        • Country: United Kingdom

        #4
        Originally posted by Flat on my back
        3 thou is the top wear limit then you'll need a re-bore, believe there is a Wossner set that starts at 81mm.

        My donor 7A block was measured at 1 thou wear on the worst bore, so get this checked first.
        So whats the next size piston after the original and what should the bore be machined too to suit? Original bore being 81mm. Will find out what the wear is once the spare block arrives in a few weeks time... Where is the best place to get proven reliable rods in a balanced set.
        1986 Coupe q - 2281cc 3B, chargecooler, 2.75" exh & downpipe, ported head, water injection, CGR box, modified MD357 turbo, 440cc injectors, high power coil.
        2004 A4 2.5TDi convertible, re-mapped to 180bhp
        2011 A5 sportback 3TDi-Backbox delete, remap

        Comment

        • Flat on my back
          S2Forum Fiend
          • Jan 2007
          • 2449
          • Country: United Kingdom

          #5
          .

          In the olden days a standard rebore was a 20 thou increase, any less really didn't increase the capacity much and that was the point.

          But now a 10 thou increase can be made cos some piston manufacturers have made these sizes available, Mahle i believe has been mentioned.

          Wossner do the set K9201D050, ...100, ...150, ...200, ...250 ranging from 81.5mm to 83.0mm. Take your pick. Personally i'd go for the biggest cc increase i can, therefore 7A block...

          From my the 3B engine manual:-

          Size Piston Cylinder bore
          Standard 80.98 81.01
          1st oversize 81.23 81.26
          2nd oversize 81.48 81.51

          Try 'aronmatic2' for the rods, or again Wossner as they do a set of pistons/rods for £900/1000.

          Regards other bits PM Aelred as his prices are always very good.

          Anything else Sir...
          Carlos.

          On the look out for less bits for my s2 saloon project. Now supporting myself by shooting for my food. www.airgunforum.co.uk

          Comment

          • Rusty
            Super Moderator
            • Jun 2004
            • 18953
            • Country: United Kingdom

            #6
            What turbo? RS2?

            Aronmatic has H section rods going at the m @ a good price.

            As for the rest of it, a good balace at BDB and some new shells, bolts and some ARP goodies will easily match expectations.

            As above, speak to Aelred for parts if you're unsure.
            Cheers'en, AndyC
            1994 ABY Coupe - Projekt Alpinweiss

            Comment

            • 20Vcqdriver
              S2Forum Maniac
              • Jun 2007
              • 829
              • Country: United Kingdom

              #7
              Originally posted by Rusty
              What turbo? RS2?

              Aronmatic has H section rods going at the m @ a good price.
              Anyone using these rods in there car without issue. Father in law always used to say 'if it's cheap it'll break'
              1986 Coupe q - 2281cc 3B, chargecooler, 2.75" exh & downpipe, ported head, water injection, CGR box, modified MD357 turbo, 440cc injectors, high power coil.
              2004 A4 2.5TDi convertible, re-mapped to 180bhp
              2011 A5 sportback 3TDi-Backbox delete, remap

              Comment

              • Rusty
                Super Moderator
                • Jun 2004
                • 18953
                • Country: United Kingdom

                #8
                Aron is, they're supposed to be the same as Scat too, plenty using those, no problems.
                Cheers'en, AndyC
                1994 ABY Coupe - Projekt Alpinweiss

                Comment

                • Flat on my back
                  S2Forum Fiend
                  • Jan 2007
                  • 2449
                  • Country: United Kingdom

                  #9
                  .

                  Well if yu dont want 'cheap'...

                  get a set of Carillo, Cosworth or Arrow...to name a few!

                  Oh...and be sat down...
                  Carlos.

                  On the look out for less bits for my s2 saloon project. Now supporting myself by shooting for my food. www.airgunforum.co.uk

                  Comment

                  • Jamo
                    Retired OG Mod
                    • Mar 2004
                    • 21750
                    • Country: United Kingdom

                    #10
                    The main difference is the weight and balancing, their all good if you get a nice set within 1g of each other.

                    I was going to run Scat then I had Pauters in the diesel block

                    Comment

                    • Rusty
                      Super Moderator
                      • Jun 2004
                      • 18953
                      • Country: United Kingdom

                      #11
                      When I spoke to Aelred, he was happy to check a set of the H beam rods over before I used them, in case they weren't useable, very helpful chap
                      Cheers'en, AndyC
                      1994 ABY Coupe - Projekt Alpinweiss

                      Comment

                      • Flat on my back
                        S2Forum Fiend
                        • Jan 2007
                        • 2449
                        • Country: United Kingdom

                        #12
                        Originally posted by Jamo
                        The main difference is the weight and balancing, their all good if you get a nice set within 1g of each other.

                        I was going to run Scat then I had Pauters in the diesel block
                        And they would have been abit short...

                        Arrow 129S5 set, for you a cheap £1020...
                        Carlos.

                        On the look out for less bits for my s2 saloon project. Now supporting myself by shooting for my food. www.airgunforum.co.uk

                        Comment

                        • 20Vcqdriver
                          S2Forum Maniac
                          • Jun 2007
                          • 829
                          • Country: United Kingdom

                          #13
                          Originally posted by Flat on my back
                          And they would have been abit short...

                          Arrow 129S5 set, for you a cheap £1020...
                          Probably don't sell many at that price!
                          1986 Coupe q - 2281cc 3B, chargecooler, 2.75" exh & downpipe, ported head, water injection, CGR box, modified MD357 turbo, 440cc injectors, high power coil.
                          2004 A4 2.5TDi convertible, re-mapped to 180bhp
                          2011 A5 sportback 3TDi-Backbox delete, remap

                          Comment

                          • Jamo
                            Retired OG Mod
                            • Mar 2004
                            • 21750
                            • Country: United Kingdom

                            #14
                            Originally posted by 20Vcqdriver
                            Probably don't sell many at that price!
                            Wanna bet

                            Ti rods cost even more http://www.pauter.com/titanium.htm

                            Comment

                            • 20Vcqdriver
                              S2Forum Maniac
                              • Jun 2007
                              • 829
                              • Country: United Kingdom

                              #15
                              Ok It's been a while but money shortages and tests on present engine to see what i could get have delayed the start of the spare block overhaul.
                              Firstly the block I have is a 7A and came with crank but no pistons/rods (not an issue as I'd have to have replaced them anyway), so now need to know what others on here recommend/use for Pistons as been told some produce more piston slap when cold than others , i.e. clearances vary between makes, So recommendations and best places to buy from please. Oh and also been told the type of rings I use also decide the type of hone hatch I get, so advice on this too.
                              I have a lot to do as this block needs work before I get anywhere near fitting pistons, see pics. Cheers.
                              Attached Files
                              1986 Coupe q - 2281cc 3B, chargecooler, 2.75" exh & downpipe, ported head, water injection, CGR box, modified MD357 turbo, 440cc injectors, high power coil.
                              2004 A4 2.5TDi convertible, re-mapped to 180bhp
                              2011 A5 sportback 3TDi-Backbox delete, remap

                              Comment

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