Radium Engineering FPD-XR Inline Fuel Pulse Damper Kit - 5/16" Hose Barb

The opening and closing of fuel injectors creates pressure pulses in the fuel rail which can lead to unstable fuel pressure. In order to achieve a safe and consistent rail pressure, a fuel pulse damper (FPD) is often necessary. The FPD's internal diaphragm will absorb oscillating pulses and stabilize fuel pressure. This correction can be measured throughout the RPM range and can often help idle surge, especially with high flow injectors. Furthermore, a fuel pulse damper can help solve erratic lean air/fuel ratio spikes, commonly experienced as "stumbling", 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. The use of an inline damper is great for applications where there is not an option for direct fuel rail mounting.

What makes Radium FPDs unique?

Along with having the flexibilty of using common fittings, Radium Engineering FPD's use a vacuum/boost reference port which allows for proper fuel pulse damper performance even at elevated fuel pressures. This becomes essential for boosted systems that use a 1:1 rising rate fuel pressure regulator.

What is the difference between FPD-R and FPD-XR?

At 1.98" tall, the FPD-R (green top) is slightly shorter than the 2.60" FPD-XR (black top) allowing it to be used in space-contrained applications. But the FPD-XR has a wider response range. Radium recommends to use the FPD-XR if you have the space.

Which damper do I choose?

The FPD-R (Fuel Pulse Damper-Range) and FPD-XR (Fuel Pulse Damper-Extra Range) both have unique base "static" fuel pressure requirements:

• FPD-R base pressure requirement = 40 - 70psi (static)
• FPD-XR base pressure requirement = 40 - 105psi (static)
  
  Base pressure is the fuel pressure measured when the fuel pump is running WITHOUT a vacuum line connected to the regulator.

IMPORTANT: The ranges above are base static fuel pressures only. Any dynamic fuel pressure created by a rising-rate FPR outside of this range is acceptable, but only when the base "static" fuel pressure is set within these ranges and the vacuum/boost reference line is connected.

Example 1:

• Vehicle: Mitsubishi EVO
• OEM Base Static Fuel Pressure: 43.5psi
• Boost Pressure: 30psi
• Rising Rate Pressure Regulator? Yes
• Can I use a FPD-R? Yes. Even though fuel pressure is 73.5psi at full boost, the FPD-R will work because the base static pressure was set within the 40-70psi requirement. However, the vacuum/boost reference line must be installed.
• Can I use a FPD-XR? Yes. Also, the vacuum/boost reference line does not need to be installed since maximum fuel pressure does not exceed 105psi.

Example 2:

• Vehicle: BMW E46 M3
• OEM Base Static Fuel Pressure: 72.5psi
• Boost Pressure: 20psi
• Rising Rate Pressure Regulator? Yes
• Can I use a FPD-R? No. Base static fuel pressure exceeds the 40-70psi requirement.
• Can I use a FPD-XR? Yes. Also, the vacuum/boost reference line does not need to be installed since maximum fuel pressure does not exceed 105psi.