Project: RS2 ABY

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  • Dan
    S2Forum Extremist
    • Jun 2008
    • 1242
    • Country: United Kingdom

    #1126
    Originally posted by driftin jo
    Bigger turbos make the same power with less boost, thus 1.9 bar does no
    equal X HP, it is turbo dependent.
    Possibly a stupid question, but how does this work?

    Surely x bar in the inlet manifold is just x bar, no matter where it came from?

    I know that if the engine is ported to increase flow, you can make more power with less pressure -- since the reason for the drop in pressure is that more air is being supplied, but more of it is flowing though -- but with the same engine, how does said engine care about the size of the turbo, beyond what boost pressure it's getting pushed into it?

    1993 ABY Coupe | BMW R1200 GS
    A6 3.0 TDI Quattro (aka Sonic's 'ring support/cargo vehicle )

    Comment

    • djh
      S2Forum Extremist
      • Jun 2011
      • 1622
      • Home: United States Current: United Kingdom

      #1127
      as I understand it

      smaller turbo making x power at 1.5 bar boost flat out

      bigger turbo making same power at 1 bar of boost not even breaking into a sweat.

      Comment

      • Rocco
        S2Forum Zealot
        • Aug 2007
        • 6393
        • Country: Spain

        #1128
        Colder air?
        RED Mitsubishi Lancer Evolution VI TME nº 16 of 250
        BLACK Mitsubishi Lancer Evolution VI TME nº 189 of 250
        LWB Audi Sport Quattro project

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        • EspenW
          S2Forum Extremist
          • Apr 2007
          • 1534
          • Country: Norway

          #1129
          Yes, colder air and (much) lower backpressure.
          1995 RS2 on Alcohol (6.8sec 100-200km/h)
          1994 80E Avant
          1986 2L Golf 2 on Alcohol

          Comment

          • driftin jo
            S2Forum Fiend
            • Sep 2007
            • 2222
            • Country: United Kingdom

            #1130
            The smaller turbo makes less power due to overall flow, a small turbo running 2 bar
            for instance may make 500hp but a bigger one could make 500hp at only 1.7 bar, this is because there is much less restriction to exhaust flow from the bigger turbos turbine.
            Think of a power in terms of pressure differential between inlet pressure and exhaust pressure.

            Put simply, as above,

            Mostly down to much lower back pressure and yes the bigger turbo will have
            lower charge temps for a given boost pressure, lower temps equal more air mass thus more fuel can be burned.

            Comment

            • Dan
              S2Forum Extremist
              • Jun 2008
              • 1242
              • Country: United Kingdom

              #1131
              Aha. That makes sense. Thanks guys.
              1993 ABY Coupe | BMW R1200 GS
              A6 3.0 TDI Quattro (aka Sonic's 'ring support/cargo vehicle )

              Comment

              • Sonic
                Administrator
                • Jul 2006
                • 5514
                • Home: United Kingdom Current: England

                #1132
                The car is undergoing some final prep for it's ring trip next weekend... Will has done a brilliant job of replacing and cleaning up some parts - now with new wishbones and solid subframe bushes.



                The brake carriers also required a little maintenance.

                S2Forum.com Administrator

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

                  #1133
                  What cams have you got in there Sonic? You need to do a spec sheet

                  Comment

                  • Sonic
                    Administrator
                    • Jul 2006
                    • 5514
                    • Home: United Kingdom Current: England

                    #1134
                    Originally posted by Jamo
                    What cams have you got in there Sonic? You need to do a spec sheet
                    I think i'd find that handy as well, there has been so much done to this car that i regularly forget things, particularly when it's out of sight, out of mind.

                    It's running ABY inlet and RS2 exhaust... i'm aware 7A would be better, but i had the RS2 cam from when i was intending to go RS2 spec with turbo, and figured i should use it.
                    S2Forum.com Administrator

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

                      #1135
                      I dont subscribe 7A is better, all cam combos have a trade off think RS2 with a KKK turbo variant is the best fit

                      Comment

                      • Sonic
                        Administrator
                        • Jul 2006
                        • 5514
                        • Home: United Kingdom Current: England

                        #1136
                        Apparently 7A would give more upper-end without any noticeable decrease low-end by removing the rs2 cam.
                        S2Forum.com Administrator

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                        • Sonic
                          Administrator
                          • Jul 2006
                          • 5514
                          • Home: United Kingdom Current: England

                          #1137
                          Rear subframe done as well, just having ARB brackets made.

                          S2Forum.com Administrator

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                          • BorisShakhov
                            S2Forum Addict
                            • Feb 2009
                            • 224
                            • Country: Russian Federation

                            #1138
                            Originally posted by Sonic
                            The car is undergoing some final prep for it's ring trip next weekend... Will has done a brilliant job of replacing and cleaning up some parts - now with new wishbones and solid subframe bushes.



                            The brake carriers also required a little maintenance.

                            Is it 8,8 strength bolts on the carriers?

                            Comment

                            • prj
                              S2Forum Zealot
                              • Mar 2010
                              • 6308
                              • Country: Estonia

                              #1139
                              Originally posted by Sonic
                              Apparently 7A would give more upper-end without any noticeable decrease low-end by removing the rs2 cam.
                              No.
                              http://tuner.ee - http://www.facebook.com/tuner.ee

                              Comment

                              • Sonic
                                Administrator
                                • Jul 2006
                                • 5514
                                • Home: United Kingdom Current: England

                                #1140
                                Originally posted by prj
                                No.
                                Must have got lost in translation then

                                What was it that you meant with 7A cams?
                                S2Forum.com Administrator

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