Announcement

Collapse
No announcement yet.

RS2 Overboost and surging issue

Collapse
X
  • Filter
  • Time
  • Show
Clear All
new posts

  • RS2 Overboost and surging issue

    I am experiencing an overboosting issue. The engine boosts strong to 1.5bar up to 2nd gear but once in 3rd it overboosts to 1.8 then cuts back to 1.5 and continues to surge up to 1.8 and back to 1.5 through 4th gear and up. I've replaced the N75 valve which fixed a problem I was having with the turbo fluttering but the surging problem persists. I smoke tested the vacuum lines and replaced a few vacuum hoses that were leaking. There does not appear to be any more boost leaks.

    I've inspected the waste gate diaphragm and it looks fine.

    The main change I've made is installing a turbo back Supersprint exhaust with a straight downpipe so the cats have been removed. Could this be causing the turbo to boost to quick for the ECU to respond? The RS2 is chipped with a set of PRJ chips.

    Any ideas what the issue could be?

    Thanks,
    Dave

  • #2
    It’s possible you have a leak that doesn’t appear till pressure gets above 1 Bar, smoke is good but not as good as pressurising the inlet tract to 1.5Bar.
    Otherwise yes, removing the cats can definitely cause overboost if a chipset is mapped near the limit. I had exactly this on my RS4 (also mapped by PRJ) when the stock exhaust was changed for a full Miltek without cats.
    However, it would only overboost occasionally when I really slammed the throttle and then it would drop into limp mode.

    S2 Coupe 3B Project


    Ur quattro restoration

    S2 Avant

    Boost is the new rock and roll!
    sigpic

    Comment


    • #3
      Originally posted by newsh View Post
      It’s possible you have a leak that doesn’t appear till pressure gets above 1 Bar, smoke is good but not as good as pressurising the inlet tract to 1.5Bar.
      Otherwise yes, removing the cats can definitely cause overboost if a chipset is mapped near the limit. I had exactly this on my RS4 (also mapped by PRJ) when the stock exhaust was changed for a full Miltek without cats.
      However, it would only overboost occasionally when I really slammed the throttle and then it would drop into limp mode.
      Thanks Newsh.

      I'll retest with pressure and see what happens. If it is being caused by the removal of the cats, would a Manual Boost Controller help limit the boost to 1.5 and stop the surging?

      Comment


      • #4
        You could use a boost controller (either mechanical or electronic) instead of the ECU to set max boost, but you would lose the ability of the ECU to reduce boost if there is a fault and therefore mask a problem which might damage the engine.
        I wonder if you have a stronger than stock spring in the WG?
        Try disconnecting the WGFV (N75) and report back on how much boost you get, it should be 0.4 Bar if the WG has a standard spring.

        S2 Coupe 3B Project


        Ur quattro restoration

        S2 Avant

        Boost is the new rock and roll!
        sigpic

        Comment


        • #5
          Hi did you solve the RS2 Overboost and surging issue.

          Comment


          • #6
            Originally posted by Canadian RS2 View Post
            Thanks Newsh.
            I'll retest with pressure and see what happens. If it is being caused by the removal of the cats, would a Manual Boost Controller help limit the boost to 1.5 and stop the surging?
            Dave did you see this rear diff lock post?

            Originally posted by A80Avant View Post
            vaccum leak found!
            which also means that a boost leak is also sorted

            RS2'd 93 UrS4 5 spd sedan
            94 UrS4 V8 6 spd manual avant

            Comment


            • #7

              Comment

              Working...
              X