ScienceofSpeed Return Fuel System Conversion


The 2006-09 factory returnless fuel system design is limited to approximately 150 L/hr (approximately 425 BHP gasoline / 280 BHP E85 at the engine) of fuel flow even when the in-tank fuel pump is upgraded.

ScienceofSpeed offers a return fuel system conversion which converts the 2006-09 fuel system to a return fuel system capable of flowing up to 320 L/hr (or 1330 cc/min per injector) when used with an appropriate fuel pump (or higher, when used with dual fuel pump carrier, coming soon). Includes high quality factory parts where possible and high quality AN fittings.

Chart: comparison between factory returnless and return fuel system on 2006-2009 showing proper fuel delivery based on demand (fuel pressure matches increase of manifold pressure) with ScienceofSpeed Return Fuel System Conversion.


  • Fuel pump sold separately. Walbro 255 L/hr, AEM 320 L/hr, or Walbro 450 L/hr pumps are compatible.
  • For applications greater than 320 L/hr, the factory fuel regulator can not bypass enough fuel. The factory fuel pressure regulator may be upgraded to the AEM Fuel Pressure Regulator and is recommended for applications using fuel pumps larger than 320 L/hr.
  • For applications using an adjustable fuel pressure regulator, fuel pressure must be measured to set base pressure. Use either the factory fuel pressure gauge set, or an aftermarket gauge, like this one.
  • The factory fuel rail may be upgraded. The AEM Fuel Rail adds a fuel pressure port, and is ideal for injectors larger than 1000 cc/min.
  • For applications using the factory fuel rail, the factory fuel rail cover kit including cover and mounting hardware is available separately. The factory fuel rail cover kit is not compatible with the AEM fuel rail.
  • Injectors made for 2006-09 S2000 are not compatible with the smaller diameter 2000-05 S2000 factory or AEM fuel rail ports. Injectors should be purchased for a 2000-05 model. If 2006-09 injectors have already been purchased, the factory or AEM fuel rails can be machined to accept the 2006-09 fuel injectors (option offered below). Available with purchase of return fuel system conversion only.


  • allows fuel to be supplied to the engine for high horsepower builds allowing the engine to run safer and more consistent with proper fuel pressure
  • does not require modification to vehicle
  • uses high quality factory parts where possible
  • high quality AN fittings
  • uses smooth inner diameter hard lines instead of loose rubber hose for best fuel flow
  • retains factory pulse damper
  • capable of 320 L/hr fuel flow or higher


  • fuel pump carrier (compatible w/ factory fuel level sensor)
  • front feed & return flexible hoses (allows engine to pivot)
  • rear feed & return semi-rigid tubes
  • smooth high flow feed & return hard lines with custom made brackets allowing factory hardware to be retained - no drilling required!
  • AN fittings & hose for feed
  • mounting brackets, retainer clips, & hardware for hard line & fuel rail
  • factory fuel rail & hardware (can be upgraded, see below)
  • factory fuel pressure regulator & hardware (can be upgraded, see below)
  • factory fuel pump carrier terminals (allows E85 fuel pump wires to be terminated in factory connector rather than using butt connectors) - ScienceofSpeed will install E85 fuel pump terminals if this kit and a fuel pump are purchased together - please ask
  • full color step-by-step detailed instructions
ScienceofSpeed Return Fuel System Conversion - S2000, 2006-09


upgrade: upgrade factory fuel pressure regulator to AEM adjustable fuel pressure regulator


upgrade: upgrade factory fuel rail to AEM machined billet aluminum fuel rail


factory fuel rail cover & hardware kit (not compatible with AEM fuel rail)


machine factory or AEM fuel rail ports for 06-09 injectors