OVERVIEW

The Radium Engineering DFPR (Dual Fuel Pressure Regulator) was designed specifically for custom fuel systems that use both direct injection and port injection. The DFPR permits independent fuel pressures for each system while using 1 fuel feed input. Furthermore, the architecture suppresses the aggressive pressure spikes created by the mechanical (positive displacement plunger-type) HPFP pump used for direct injection. FPR1 is used for direction injection and FPR2 is used for port injection.

MOUNTING

As shown below, an anodized aluminum bracket and M6x1mm hardware are provided.

Reference the dimensions below to confirm fitment in the vehicle.

The flat head stainless steel screws permit the DFPR to be flush mounted to a flat surface.

PLUMBING

The DFPR is designed to be plumbed upstream (before) the HPFP and port injection fuel rail(s).

PUMP IN

• Threads: 3/4-16" (8AN ORB)
• This port is the only inlet. The low pressure fuel pump (LPFP) outlet should be plumbed to a low micron fuel filter and then secured to this port.

FPR1 OUT

• Threads: 3/4-16" (8AN ORB)
• This port should be plumbed directly to the high pressure fuel pump (HPFP) inlet.

FPR2 OUT

• Threads: 3/4-16" (8AN ORB)
• This port should be plumbed directly to the port injection fuel rail(s). Plug the opposing end of the fuel rail(s). NOTE: If the engine does not have port injection, this port can be plugged with no affect to FPR1. For FPR1 to work efficiently, spin the FPR2 knob fully counterclockwise.

RETURN

• Threads: 3/4-16" (8AN ORB)
• This port should plumb directly to the fuel tank (or fuel cell). NOTE: If there is no return port on the fuel tank, these barbed hose adapters may be an option to return fuel into the filler pipe.

AUXILIARY SENSOR PORT (FPR1)

• Threads: 1/8"-27 NPT
• To monitor FPR1, this ports can be used for gauges, sensors, etc. A plug is included.

AUXILIARY SENSOR PORT (FPR2)

• Threads: 1/8"-27 NPT
• To monitor FPR2, this ports can be used for gauges, sensors, etc. A plug is included.

FUEL PRESSURE ADJUSTMENT

RA-series regulators feature the first tool-less pressure adjustment. A jam nut and set screw are no longer required. With a simple turn of the knob, pressure will be increased or decreased. Additionally, there are no inherent air (vacuum/boost) leaks through the threads that traditionally a smoke detector would pick up.
To aid in adjusting pressure, there are incremental detents that provide haptic feedback to the user. Every detent permits 1psi (+/-0.5psi) of adjustment depending on current fuel pressure.

NOTE: FPR2 pressure will always be equal to or less than FPR1 pressure. It cannot physically be higher.

FUEL PRESSURE STABILITY

With years of track and bench testing data, the RA-series regulators have been refined to optimize pressure management. A newly designed single stainless steel return orifice generates laminar flow that enhances stability control.

• Minimum Pressure: 18.5psi (1.3bar)
• Maximum Pressure: *N/A

*This is rhetorical. The maximum pressure is dependent on the relief valve inside the pump or the maximum current the fuel pump controller allows. 

1:1 RISING RATE VACUUM REFERENCE

NOTE: If FPR2 is 1:1 boost referenced, FPR1 pressure will increase accordingly to match FPR2.

1. Barbed Fitting: A black zinc-plated 3/16" (5mm) barb machined from high strength steel that is compatible with the following vacuum hoses: 5/32" (4mm), 3/16" (5mm), and 7/32" (6mm).
2. 3AN Male Fitting: A black zinc-plated adapter machined from high strength steel that is compatible with 3AN hose ends.
3. Push-To-Connect: A nickel-plated brass fitting with Buna-N O-rings that is compatible with hard plastic 1/4" OD tubing.
4. Vacuum Plug: A black oxide stainless steel screw that is used to maintain a constant (non dynamic) fuel pressure. Beginning in the mid 1990s, vehicle manufacturers started transitioning to returnless fuel systems to lower EVAP emissions. To keep temperatures lower, these regulators are mounted inside the tank and do NOT have the ability to be vacuum referenced. This plug would be required in this scenario.

NOTE: When installing the vacuum fitting, it is recommended to use a wicking medium-strength threadlocker.

RA-series regulators feature a 360 degree swiveling vacuum reference port that is double O-ring sealed. This is the first in the industry. It permits the installer to quickly point the vacuum fitting in any direction with no tools required. There are 4 interchangeable 10-32 threaded vacuum port fittings provided to cover all scenarios.

FUEL COMPATIBILITY

All RA-series regulators are suitable with all gasoline types including unleaded, leaded, oxygenated, and pre-mixes. Furthermore, they are compatible with alcohol blends of fuel including methanol, ethanol, and E85.