This kit permits all previous Radium Engineering adjustable fuel pressure regulators to be converted to an RA-Series FPR. This will add all of the newest features as well as performance enhancements to older regulators

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.

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.

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

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.

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.

FUEL COMPATIBILITY
This RA-series conversion kit is 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.

The graph below shows the minimum fuel pressure the regulator can achieve as a function of pump flow rate. For example, if you have two pumps that flow 320LPH (total 640LPH), the approximate minimum pressure the regulator can achieve is about 30psi. If an OEM fuel pressure regulator sees 640LPH for instance, it will likely not be able to bypass enough fuel.