• 13mm wrench or socket + ratchet
  • die grinder
  • carbide burr

  • Labor:

    The 1989-1991 Kouki FC3S turbo wastegate design is superior to the earlier 1986-1988 FC3S Zenki turbo wastegate design.  The Kouki wastegate had two holes that allowed exhaust gases to bypass both turbine passages within the "independent twin scroll" turbo.  In contrast, the Zenki turbo wastegate only bleeds exhaust gases from one passage of it's "twin scroll" turbo - this inferior design will produce boost creep from freer flowing exhaust systems!  Boost creep is BAD.  Below is a desciption of how we port the Zenki wastegate passage to promote better boost control by the wastegate system.

    FC3S Pro:  Zenki Turbo Wastegate Porting
    Zenki turbo wastegate exposed
    Notice only single wastegate passage from one of the runners.
    Also notice the vague outline where the flapper door contacts the hole.
    Kouki turbo wastegate exposed
    Notice two wastegate wastegate passages from both runners.
    If you have a Kouki turbo, we do have a Kouki turbo wastegate porting page here:
    Zenki turbo wastegate ported
    Using the outline of the flapper door, we ported approximately 0.5mm smaller than the flapper door diameter.
    Zenki turbo wastegate ported, lighted
    Using a light to highlight the rear portion of the passage, this shows the backcutting of the passage for smoother flow.
    Comparison before and after
    Before and after pics of Zenki wastegate.
    Although not to scale, the ported wastegate is about 2mm wider in diameter than the stock, non-ported hole.

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