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Last Post 06 Jun 2017 08:59 PM by  sjfehr
Need help clarifying if these modifcations would be legal for STS
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New Member
New Member

06 Jun 2017 12:28 AM

    Hi everyone,

    I apologize in advance for asking a bunch of newbie questions but I could really use some clarification here.  I have currently run a handful of events in STS with my car and I need to make some necessary drivetrain and exhaust repairs soon before I do another event. 

    First and foremost am I correct in the assumption that if the rulebook doesn’t explicitly mention it then it’s not legal for my class?

    If that is true it probably answers my other questions now but I’d like to ask for clarity sake:


    1)   Nothing is said about the clutch or flywheel at all in the Street Touring Section.  Can I assume that it means No aftermarket components are allowed?

    No component Lightening is allowed? i.e. machining OEM flywheel?

    Could I substitute a different OEM pressure plate from another build code of the same transmission family to make it more durable?  The same basic trans platform was used for 12 or 14 years.

    Can I only use a 100% OEM clutch?

    2)  It says that:

     “Exhaust manifolds, headers, downpipes, and associated EGR tubes may be replaced with alternate units. Exhaust exit may be relocated provided it meets Section 3.3.3.B.16. Relocation of the oxygen sensor on the header is permitted.” 

    Should I take this to mean that I can run an aftermarket header?

    And I’m more concerned about this:

     “E. Catalytic converters – Any catalytic converters are allowed.

    STU, STR, STX, STS, STF – Catalytic converters must attach within 6” (152.4 mm) of the original unit. Multiple catalytic converters may be replaced by a single unit. The inlet of the single replacement converter may be located no further downstream than 6” (152.4 mm) along the piping flow path from the original exit of the final OE converter.”

    So this means that I MUST have a catalytic converter and that I can only relocate it up to 6” from its OEM location on the pipe?  The only aftermarket headers on the market for my car are called “race headers” and are designed to be run without the CAT.  I’d have to see if I could even have exhaust fabed up that would fall within the 6” rule. 

    3)  The rule book states:  “G. Any mechanical shift linkage may be used.”

    Does this mean that I CAN modify the shift linkage with a weighted shift rod and short shift kit?

    Advanced Member
    Advanced Member

    06 Jun 2017 08:59 PM
    ST inherits the Street allowance for clutch disks and pressure plates: it can be aftermarket, but must remain essentially identical to the standard part (same type, size, material, etc.) You can't change the flywheel.

    You can run aftermarket exhaust headers, but you must still run a cat in about the same place as OEM. ST is still ostensibly street legal, which means keeping emissions systems street legal, too.

    And, yes, you can install a short shift kit!

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