The stock fuel system of the R35 GT-R is not adequate for anything much more involved than a mild reflash. The stock fuel pump and injectors do not have much capacity headspace and even simple bolt-on mods will push them to where the engine can lean out under load with disastrous consequences. In our case, we wanted to make the most power possible with bolt-ons at this stage of the development of our car and also wanted our project R35 GT-R to be able to run on E-85 with requires at least 30% more capacity to make the same power as gasoline. This was going to require quite a bit more fuel than the stock fuel system could provide. We were going to have to go in and modify our fuel system for more capacity and while we were in there, we decided that we would do things so we could have enough fuel to reach our eventual goal of 1000 whp. To do this we used parts from Radium Engineering and Cobb Tuning.
Until recently if you needed more fuel capacity, most people crudely modified the stock Nissan fuel pump hanger assembly to take two high-volume fuel pumps. Although this worked, it left a lot to be desired from a fuel starvation standpoint, especially during track driving with a partially full tank aspect. These jury-rigged solutions did not scavenge the far side of the tank well and also let air get sucked up under hard cornering, acceleration, and braking.
To solve this cleanly and easily we used Radium Engineerings fuel hanger. The Radium fuel hanger completely replaces the factory in-tank fuel pump unit and permits up to three 39mm diameter aftermarket pumps to supply fuel to the engine. It is a total bolt-in solution and no fabrication or modification to the vehicle is needed at all. The fuel pumps are housed in an aluminum in-tank surge tank that is kept full during operation. This ensures that fuel starvation does not occur, even during aggressive driving. The fuel pumps outlet port is -10AN ORB female threaded, while the return port is -8AN ORB female threaded. The system is compatible with alternative fuels such as methanol, ethanol, E85, etc.
The top of the Radium fuel pump hanger that closes off the OEM fuel tank features custom-designed stainless through electrical studs that easily handle the fuel pumps high current demand that multi-pin bulkhead connectors lack. These serviceable connections are hermetically sealed and impervious to all standard and exotic fuels. Nonconductive anodized aluminum acorn nuts are provided to prevent any accidental short-circuiting. Electrical hardware is included for the fuel pump(s) and OEM sensors. Furthermore, the in-tank wiring is insulated with high quality chemically resistant PTFE. The factory temperature sensor and fuel level sender is reused.
The GT-R saddlebag style fuel tank uses two OEM venturi jet pumps. They supply fuel from both sides of the tank to the OEM pump bucket and are driven by fuel returning from the regulator. When the fuel pumps are upgraded, these venturi jet pumps become a restriction in the return line, resulting in elevated fuel pressures and unreliable regulator performance. By reconfiguring the venturi jet pump plumbing, Radium Engineering has kept its functions without impacting the returning fuel from the regulator. This allows the pumps to be upgraded without fuel pressure concerns.
In addition to the venturi jet pumps scavenging fuel, the pressure regulator return also keeps the large collector box filled with fuel. Additionally, the Radium Engineering system incorporates a one-way fill valve shown here, integrated to the bottom of the collector box that allows fuel in, but not out. All of the components work together to keep the collector box filled with fuel and prevent fuel pump starvation. This is a far cry from cobbling another pump into the stock plastic hanger!