Charles at CJ Motorsports pointed out to us that many forced induction cars including the 370z/G37’s big brother the GTR uses a return fuel system. In his words, the advantages are numerous and compounding. He further stated that having the external regulator in the engine bay allows a 1:1 vacuum reference line. The regulator can increase fuel rail pressure at the same rate boost climbs. This is important because the boost pressure in the intake manifold will work against the fuel pressure in the injectors. This allows for the effective fuel pressure to remain steady against the boost. It also makes the best use of the fuel injectors.
It’s Charles’ belief that there are no solid power limits to a particular fuel system component or layout but any forced induction VQ engine should have a return system as it will provide more consistent tuning than a returnless system. On his own car Charles would want a return fuel system at the 400-450 wheel horsepower mark. We take this as good advice from a guy who has a 370z that runs the quarter-mile in 9.9 seconds at 142mph.
For fuel injectors we’re running Injector Dynamics 1050x fuel injectors. Both Charles from CJ Motorsports and Omar at UpRev recommended using these motorsports grade injectors from Bosch. The corrosion-resistant internals for the 1050x allows this injector to be used with hygroscopic fuels like ethanol. The nominal flow rate for these injectors is 1065cc/min at 43.5 psi. CJ Motorsports ran their twin-turbo Z up to 670 wheel horsepower with these injectors and figure we figure this will be a good stopping point for us.
To get the fuel to the injectors we chose an Aeromotive 340 stealth pump (part #11542). CJ Motorspots used this pump in their Z up to 580 whp. While they didn’t hit the flow limits of the pump it was unclear how much more flow was possible. The stealth 340 flows more than 340 lph at 40 psi allowing for more flow for those using factory lines. Part of our upgrade with the S1.SE system is upgrading the fuel lines for even more flow. Due to the superior flow characteristics, the 340 is a good candidate for forced induction applications as fuel pressure drops as boost pressure increases. The Aeromotive Stealth 340 is also e85 compatible.
With more fuel flowing it also means we’re putting added stress on the factory electrical system. CJ Motorsports recommended upgrading the fuel pump wiring with their DeatchWerks wiring kit (p/n 900.0050). The power cable is 12ga and 15′ long with a 25-amp inline fuse and a 40 amp relay and socket. We also opted for the center pump strainer p/n 900.1225 and note that this is not a replacement for the factory fuel filter as stated it’s to strain any objects that may be in the fuel tank. This pre-filter (strainer) is enough to protect the fuel pump but not enough to protect the injectors.