Project GD Subaru STI, High Power Fuel System Upgrades!

When last tuning our STI with Cobb’s flex-fuel system, we had maxed out our Mass Air Flow Meter, fuel pump and had our injectors going at the maximum duty cycle all on the stock bottom end.  At the time, this was ok because at 400whp we were probably a little beyond what the stock bottom end could take for very long.  Now with our new engine from IAG, we are able to safely turn up the wick and to do this we need some new components from Radium Engineering, Cobb Tuning, IAG Performance, and Injector Dynamics to see us to about 500whp.

Read all about Project STI here!

The first place that needed some serious upgrading was our fuel pump. Previously we had a stock location 340LPH pump which was more than enough with gasoline but with E85, and its required higher volume of fuel we started to see the fuel pressure slightly drop on long wide-open throttle pulls.  When trying to compensate with more injector pulse duration, we started to run out of duty cycle.  Our pump was also not rated for E85 which was probably going to seriously limit its service life as well.  Instead of just getting a bigger pump, we instead decided to really upgrade our fuel system with a Radium Engineering Fuel Hanger which is specially engineered for our car.

For the fuel pumps’ pass-through wiring, noncorroding stainless electrical studs easily handle the high current demand that compact bulkhead connectors lack. These serviceable connections are properly sealed and impervious to all standard and exotic fuels. The low-profile design keeps all wiring tucked nicely underneath the OEM cover plate. Nonconductive acorn nuts which are not shown here are provided to prevent any accidental short circuits with the car’s body. Stainless steel crimp-on ring terminals and heat shrink are provided for external wiring connections

The high-quality in-tank wiring is insulated with chemically resistant ETFE.  This resists all conventional and exotic fuels. There are terminals for 2 fuel pumps, the fuel level sensor, and fuel temperature sensors.  There are built-in provisions for the OEM fuel level sensor.

The hanger features a venturi jet pump with a new integrated pressure relief valve that is optimized for a high flow pump.  This efficiently pumps the fuel from the far side of the saddleback tank better than the stock system does.