ScienceofSpeed Return Fuel System Conversion - S2000, 2006-09


The 2006-09 factory returnless fuel system design is limited to approximately 150 L/hr (approximately 425 BHP gasoline or 280 BHP E85 at the engine, 10-15% less at the wheels) of fuel flow even when the in-tank fuel pump is upgraded. As fuel pressure drops off, the injectors can no longer flow enough fuel to support power above these limits and fuel delivery becomes unstable and unsafe for the engine.

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.

The chart is a data log from a turbocharged engine producing 10 PSI of manifold (boost) pressure). The chart demonstrates the dramatic difference of fuel rail pressure between the factory 2006-09 returnless fuel system (blue) and ScienceofSpeed return fuel system (pink).

  • Fuel pump: is not included, and is required for installation. Walbro 255 L/hr, AEM 340 L/hr, or Walbro 450 L/hr pumps are compatible.
  • Fuel injectors: Injectors made for 2006-09 S2000 are not compatible with the smaller diameter 2000-05 S2000 factory fuel rail ports. Injectors should be purchased for a 2000-05 model. If 2006-09 injectors have already been purchased, the factory fuel rails can be machined to accept the 2006-09 fuel injectors (option offered below). Available with purchase of return fuel system conversion only.
  • Fuel rail: The factory fuel rail is the only option available at this time.  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 aftermarket fuel rails. (Currently not available)
  • Fuel pressure regulator: For applications greater than 320 L/hr, the factory fuel regulator can not bypass enough fuel. The included 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.
  • Fuel pressure setting for aftermarket regulator: 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, a sensor connected to the engine management system (if supported), or a simple gauge like this one


  • 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 permanent modification to vehicle.
  • Uses high-quality factory parts where possible.
  • High quality AN fittings.
  • Uses factory feed and return pipes for transfer between front and rear of car. The smooth inner diameter of hard pipes flow better than loose hose.
  • Includes high-quality Teflon stainless braided front & rear high-pressure feed hoses and rear return hose featuring larger than factory diameter.
  • 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).
  • Utilizes factory high flow feed & included return hard pipes with custom made brackets allowing factory hardware to be retained - no drilling required!
  • AN fittings & hose for feed & rear return.
  • Mounting brackets, retainer clips, & hardware for hard pipe & fuel rail.
  • 3D fiber reinforced nylon fuel hose clamp, designed to replace factory clamp, is designed for the included larger hoses.
  • Factory fuel rail & hardware (can be upgraded, see below).
  • Factory fuel pressure regulator & hardware.
  • Factory fuel pump carrier terminals (allows E85 fuel pump wires to be terminated in factory connectors rather than using butt connectors).
  • 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


machine factory fuel rail ports for 06-09 injectors