Radium Engineering FPD-XR Inline Fuel Pulse Damper

Tame Fuel Pressure Pulses at the Rail with the Radium FPD-XR Inline Pulse Damper

The Radium Engineering RAD20-0200 FPD-XR Inline Fuel Pulse Damper is a precision billet aluminum device designed to absorb oscillating fuel pressure pulses generated by injector opening and closing events. Installed in-line on the high-pressure fuel feed line between the pump and the rail, the RAD20-0200 uses an internal vacuum and boost-referenced diaphragm to smooth fuel pressure fluctuations across the entire RPM range, reducing idle surge, eliminating lean spikes caused by rail pressure instability, and improving overall tune consistency. Unlike simpler fixed-pressure dampers, the RAD20-0200 features a 1/8 NPT vacuum and boost reference port that allows the diaphragm response to scale with manifold pressure, making it particularly effective on rising-rate fuel pressure regulator setups and boosted applications where base static fuel pressure falls between 40 and 105 PSI. The RAD20-0200 is safe for all fuel types including E85 and installs in any orientation, including upside down.

Key Features

• Absorbs fuel rail pressure pulses to stabilize fuel pressure across the RPM range
• Base static fuel pressure requirement: 40 to 105 PSI (wider range than the FPD-R)
• Vacuum and boost reference port allows proper response with rising-rate fuel pressure regulators
• Anodized aluminum housing with laser-engraved top; 2.60 inches tall
• 0.69 inch center bore with two inline 8AN ORB (3/4 inch 16 UNF) inlet and outlet ports
• 1/8 NPT female center port accepts pressure gauge, sensor, or the included plug
• E85 and gasoline-resistant internal diaphragm
• Stainless steel M6 mounting hardware allows mounting at any angle including inverted
• Compatible with all fuel types including gasoline, race fuel, and E85 blends
• Not recommended for the low-pressure side of mechanical fuel pumps
• Radium Engineering limited warranty

Specifications

What's Included

• 1x Radium Engineering RAD20-0200 FPD-XR anodized aluminum housing with laser-engraved top
• Anodized aluminum body with female 8AN ORB ports
• Anodized aluminum ORB adapter fittings (8AN size)
• Gasoline and E85-resistant internal diaphragm (pre-installed)
• Stainless steel M6 mounting bolts and nuts
• 4mm ID rubber vacuum reference hose
• Vacuum hose Y-fitting
• 1/8 inch NPT hex plug

Frequently Asked Questions

The RAD20-0200 absorbs the high-frequency pressure pulses created by fuel injectors opening and closing. Each time an injector fires, it creates a pressure wave that travels back through the fuel rail and feed line. Without a pulse damper, these waves cause momentary pressure instability at adjacent injectors, leading to inconsistent fuel delivery, lean spikes, idle surge, and tuning difficulty. The RAD20-0200's internal diaphragm absorbs these pulses and keeps rail pressure stable shot to shot, improving fueling consistency and making the tune more predictable.

The FPD-R (Range) has a base static pressure requirement of 40 to 70 PSI and a shorter 1.98 inch housing for space-constrained applications. The RAD20-0200 FPD-XR (Extra Range) has a taller 2.60 inch housing and a wider base static pressure range of 40 to 105 PSI. Radium recommends the FPD-XR for most applications where space allows, as it covers a broader pressure window and does not require a vacuum reference line connection when base fuel pressure stays below 105 PSI.

If your base static fuel pressure is between 40 and 105 PSI and you do not use a rising-rate fuel pressure regulator, the vacuum reference line is optional and the 1/8 NPT port can be plugged with the included plug. If you use a rising-rate FPR, connecting the vacuum and boost reference line is recommended to ensure the diaphragm responds correctly to boost-elevated fuel pressures. The 4mm vacuum hose and Y-fitting are included to make this connection straightforward.

Yes. The RAD20-0200 uses a gasoline and alcohol-resistant diaphragm and FKM O-ring seals, making it fully compatible with E85 and all ethanol blend fuels. It is also compatible with standard pump gasoline and race fuels. Do not use with diesel fuel.

For best results, install the RAD20-0200 as close to the fuel rail as possible on the high-pressure feed line, between the fuel pressure regulator and the fuel rail inlet. The damper is not flow-direction specific, so either port can serve as the inlet. Do not install it on the low-pressure return side or upstream of a mechanical fuel pump's inlet.

Yes. The M6 stainless steel mounting hardware allows the RAD20-0200 to be installed at any angle, including completely inverted. The diaphragm operates correctly in all orientations. Drill two 17/64 inch (6.75mm) mounting holes spaced 1 inch (25.4mm) apart on the mounting surface, insert the M6 bolts, and tighten with a 10mm socket and a 5mm Allen wrench.

Yes. The RAD20-0200 includes anodized aluminum 8AN ORB male adapter fittings for connecting 8AN hose lines. The base housing has 8AN ORB (3/4 inch 16 UNF) female ports. If you need to connect 6AN hoses or 5/16 inch rubber fuel hoses, the corresponding kit versions (FPD-XR-06 or FPD-XR-01) include the appropriate adapter fittings instead.

Yes. Idle surge caused by rail pressure instability is one of the primary applications Radium designed the FPD series to address. Many high-performance OEM engines including the Toyota 2JZ-GTE, Nissan VQ35DE, and Subaru EJ20 and EJ25 use inline fuel pulse dampers from the factory for this exact reason. The RAD20-0200 is particularly effective on builds with large injectors, high idle fuel pressure, or aggressive cams where small pressure variations cause disproportionately large fueling errors.

You will need a 10mm socket wrench and a 5mm Allen wrench for the mounting hardware, an AN fitting wrench or crow foot for tightening the 8AN ORB adapter fittings, a drill and 17/64 inch bit for the mounting holes, and PTFE paste if connecting the 1/8 NPT vacuum port. The fuel system must be depressurized before beginning installation.

Installation Overview

1. Depressurize the fuel system by removing the fuel pump fuse, starting the engine until it stalls, and then cranking briefly with the fuel pump disabled to release any residual rail pressure.
2. Select a mounting location on the firewall or engine bay as close to the fuel rail inlet as possible, away from excessive heat sources.
3. Drill two 17/64 inch (6.75mm) mounting holes spaced 1 inch (25.4mm) apart and secure the RAD20-0200 housing using the included M6 stainless steel bolts and nuts.
4. Lubricate the FKM O-rings on the adapter fittings with clean engine oil, then thread the adapter fittings into the 8AN ORB ports on the housing and tighten to specification.
5. Re-route the high-pressure fuel feed line through the RAD20-0200: connect the line from the FPR outlet to one port, and run a new hose from the opposite port to the fuel rail inlet. The damper is not flow-direction specific.
6. If connecting the vacuum reference port, apply PTFE paste to the 1/8 NPT threads and install the Y-fitting and vacuum hose, routing to the intake manifold vacuum source. If not using the vacuum port, install the included 1/8 NPT hex plug with PTFE paste applied.
7. Restore fuel pump power and cycle the ignition several times to prime the system before starting the engine.
8. Start the engine, check all fittings and connections for leaks, and verify fuel pressure with an external gauge.

WARNING: This product can expose you to chemicals including lead and phthalates, which are known to the State of California to cause cancer and reproductive harm. For more information go to www.P65Warnings.ca.gov.