Powertrain Rejuvenation: The Rules are the Limit (ASP)

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  • I have made it abundantly clear, because I am too honest when it comes to racing, that I’ve installed a lighter-than-stock flywheel in my WRX. This makes me ineligible for the stock, or even STX SCCA classes, and relegates me to A-Street Prepared (ASP). My car is woefully outgunned in this class, but luckily a good opportunity to change classes has arrived. When I pull the motor to do the refresh that I’m planning, I can swap back to my stock flywheel! However, for due diligence, let’s take a look at all the things I can do to my engine based on the ASP rulebook.┬áThe notes below are compiled from the 1/17/2017 release of the SCCA ASP rule set, which can be found here.

Oil Pan/Engine Lubrication

  • MUST retain standard type lubricating system (no dry-sump)
  • Any oil pan/baffling/windage tray is acceptable
  • Oil cooler is acceptable if positioned in the opening of a permitted “spoiler”

Thermal Control

  • Heat shields are allowed (and that’s all it says about that)
  • ANY radiator such that:
    • The core is no smaller in any dimension than the OEM radiator
    • The radiator must use the stock mounting locations
    • Radiator capacity and dry weight may be no less than stock
  • Stock fans can be removed, electric fans of any variety can be added
  • ANY transmission cooler is allowed


  • Any intake manifold is accepted, consequent throttle cable mods are allowed
  • Air cleaners may be modified or removed
  • Any size and configuration of intercoolers is accepted, but the body and chassis may not be modified in order to install the intercooler setup of your choosing
  • NO changes to the turbo (not bigger, not greater quantity, nor any mods)
  • NO changes to the wastegate (neither location, quantity, nor size)
  • NO changes to blow-off valves
  • ANY compressor bypass valve is allowed
  • Otherwise electronic or mechanical boost regulators are allowed
  • Intake water injection systems are allowed
  • Intake manifold openings may be matched to intake ports


  • ANY fuel lines under 1/2″ I.D. and any fuel pump
    • A return line is allowed and may serve no other purpose
    • All lines must only be as long as necessary


  • ANY exhaust manifold and muffler system is allowed, such that it is “quiet” and terminates behind the driver
  • Stock exhaust heat shields may be removed (#WeightReduction)
  • Manifold openings may be matched to exhaust ports


  • ANY engine or transmission mount, as long as it is mounted in the stock location
  • “A bolt-on torque suppression system may be used”… Can we play with the pitch stop?
  • No mounting plates may be used


  • ANY metallic flywheels is allowed
  • ANY nonmetallic clutch friction material is allowed
  • ANY hydraulic line is allowed
  • ANY clutch slave cylinder is allowed
  • ANY mechanical shift linkage is allowed
  • LSDs and welded diffs are allowed, as well as housing mods required for the installation of the limited slip differential


  • Max cylinder over-bore = 0.0472″, and associated oversized piston is allowed… No wear allowance beyond this however
    • Oversized pistons must be same as stock in the following areas:
      • Mass
      • Dome shape
      • Ring configuration
      • ie: No trick pistons!
  • Rotating and reciprocating parts may be balanced by not lightened
  • Heads may be decked to manufacturer’s spec or 0.010″ max if not specified
  • ANY crankshaft damper or pulley is allowed
  • ANY ACCESSORY belt or pulley is allowed
  • NO trick cam shafts.. standard unless required to change timing, and only for timing


  • Plastic engine cladding may be removed (#WeightReduction)
  • Cruise control system may be removed in its entirety

As you can see, ASP is a big bite out of the modifications apple! Certainly a maxed out ASP WRX would well exceed my budget for the year. Next I’ll take a look at the STX rules to confirm my next move.

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