Radium Engineering Barb FPD-XR Fuel Pulse Damper Inline Kits

The opening and closing of fuel injectors create pressure pulses in the fuel rail, which can lead to unstable fuel pressure. To achieve safe and consistent rail pressure, a Fuel Pulse Damper (FPD) is often necessary. The FPD's internal diaphragm absorbs the oscillating pulses and stabilizes fuel pressure. This correction can be measured across the entire RPM range and commonly helps with idle fluctuations, especially with high-flow injectors. Furthermore, a Fuel Pulse Damper can help fix erratic lean air/fuel mixture spikes, commonly perceived as "misfires," that are difficult to tune out.
Many high-performance OEM engines use an in-line fuel pulse damper from the factory, including the Toyota 2JZ-GTE, Nissan VQ35DE, and Subaru EJ20/EJ25. Using an in-line damper is ideal for applications where direct mounting to the fuel rail is not possible.
NOT RECOMMENDED FOR THE LOW-PRESSURE SIDE OF MECHANICAL FUEL PUMPS

What Makes Radium FPDs Unique?

In addition to the flexibility of using common connections, Radium Engineering FPDs use a vacuum/boost reference port that allows for proper fuel pulse damper operation even at elevated pressures. This is essential for boosted systems running a 1:1 rising rate fuel pressure regulator.

What Is The Difference Between The FPD-R And FPD-XR?

At 2 inches tall, the FPD-R (green cap) is slightly shorter than the 2.6 inch FPD-XR (black cap), allowing for use in space-constrained applications. However, the FPD-XR has a broader response range. Radium recommends using the FPD-XR if the space is available.

Which Damper Should I Choose?
The FPD-R (Fuel Pulse Damper-Range) and FPD-XR (Fuel Pulse Damper-Extra Range) have unique "static" base fuel pressure requirements:

FPD-R Base Pressure: 40 - 70 psi (static)

FPD-XR Base Pressure: 40 - 105 psi (static)

Base pressure is the fuel pressure measured when the fuel pump is running WITHOUT a vacuum line connected to the regulator.

IMPORTANT: The above ranges are for static base fuel pressure only. Any dynamic fuel pressure generated by a rising-rate fuel pressure regulator outside this range is acceptable, but only if the "static" base fuel pressure fits within these ranges and the vacuum/boost reference line is connected.

Example 1:

Vehicle: Mitsubishi EVO
OEM Static Base Fuel Pressure: 43.5 psi

Boost Pressure: 30 psi

Rising Rate Regulator? Yes

Can I use an FPD-R? Yes. Even though fuel pressure will be 73.5 psi at full boost, the FPD-R will work because the static base pressure fit within the 40-70 psi range. However, the vacuum/boost reference line must be installed.

Can I use an FPD-XR? Yes. Additionally, the vacuum/boost reference line is not required to be installed, as the maximum fuel pressure does not exceed 105 psi.

Example 2:

Vehicle: BMW E46 M3
OEM Static Base Fuel Pressure: 72.5 psi

Boost Pressure: 20 psi

Rising Rate Regulator? Yes

Can I use an FPD-R? No. The static base fuel pressure exceeds the 40-70 psi range.

Can I use an FPD-XR? Yes. Additionally, the vacuum/boost reference line is not required to be installed, as the maximum fuel pressure does not exceed 105 psi.

Features

The kit includes an anodized aluminum housing with a 0.69" diameter center bore and two in-line inlet/outlet ports machined with 3/4"-16 UNF thread for 8AN ORB fittings. Depending on the fuel feed hose size, 3 kits are available which include different male adapters (-6AN, -8AN, Barb type). These fittings seal to the housing using FKM O-rings. A 1/8" NPT female port threads into the center of the Fuel Pulse Damper. A fuel pressure gauge or other sensors are commonly used here to acquire pressure or temperature data.

With the included M6 bolts and nuts, the FPD kit can be mounted at any angle, even upside down. For best results, the damper should be installed as close to the fuel rail as possible. Like any fuel system component, the FPD kit should be kept away from excessive heat areas.

This product is safe for use with all fuel types, including alcohol blends such as E85.

Connections

The in-line dampers are offered in three different versions; selection should be made based on the hose connection type needed.

The -01 version is an excellent choice for 5/16" rubber fuel hoses. Hose clamps are required.
The -06 version includes adapters to connect -6AN hoses.

The -08 version includes adapters to connect -8AN hoses.

Package Contents:

- Anodized Aluminum/Laser Etched Cap, R=range or XR=extra range

- Anodized Aluminum Body with -8AN Female ORB Ports

- Anodized Aluminum ORB Adapters, size selectable

- Gasoline and Alcohol (E85) Resistant Diaphragm

- Stainless Steel M6 Mounting Bolts and Nuts

- Rubber Vacuum Hose, 4mm ID

- Vacuum Hose Y-Fitting

- 1/8" NPT Plug

Instructions PDF