Turbocharger, Intercooler, Diverter/Blow-Off Valve

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  • A good explanation of "turbo surge":
    "Typically, surge occurs immediately after the throttle plate is closed while the turbocharger is spinning rapidly, such as between shifts or when decelerating. During surge, air pressure increases between [the compressor and throttle body], which reduces the air flow at the compressor. If the air flow falls below a certain point, the compressor wheel (the impeller) looses its "grip" on the air. Consequently, the air in the compressor stops being propelled forward by the impeller and is simply spinning around with the wheel, which is still being rotated by the exhaust gas passing through the turbine section. When this happens, the pressure build-up at the discharge opening forces air back through the impeller causing a reversal of air flow through the compressor."
  • Another explanation of "surge":
    "Surge is the situation when the compressor "spits out" more air than the engine can swallow, which causes a backup of air at the intake and it actually creates reverse-flowing pressure waves that can be very damaging to the turbo."

  • Pic of a busted diverter valve from a 2006 MkV GTI:
    Busted diverter valve IMAGE 00027.jpg

  • Stock (top) versus Neuspeed (bottom) turbocharger discharge pipe:
    Stock ic discharge pipe vs NS.jpg
    Stock (top) versus Neuspeed (bottom) turbocharger discharge pipe's flange.
    Stock ic discharge pipe flange vs NS.jpg


  • How to remove the noise pipe [vwvortex] in a MkV GTI:
    • Remove the 5/16" bolt 5/16 hex bit) on top of the radiator cover]:
      How to remove noise pipe IMG 0647 Medium.JPG
    • Remove the T27 Torx screw inside the engine bay below the washer fluid resevoir:
      How to remove noise pipe IMG 0648 Medium.JPG
    • Loosen metal clamps: on top of the pipe by the firewall, and by the oil dipstick:
      How to remove noise pipe IMG 0649 Medium.JPG
    • Remove noise pipe:
      How to remove noise pipe IMG 0642 Medium.JPG