Radium FPD-R Fuel Pulse Damper — 3/8" NPT

The opening and closing of fuel injectors creates pressure pulses in the fuel rail that can lead to unstable fuel pressure. A fuel pulse damper (FPD) absorbs these oscillating pulses via an internal diaphragm to stabilise rail pressure throughout the RPM range. This can help resolve idle surge (especially with high-flow injectors) and erratic lean AFR spikes commonly experienced as “stumbling” that are difficult to tune out.

Radium FPDs feature a vacuum/boost reference port, allowing proper damper performance even at elevated fuel pressures — essential for boosted systems running a 1:1 rising-rate fuel pressure regulator. The anodized aluminium housing offers two selectable threaded male fittings: 8AN ORB (Viton O-ring seal) or 3/8" NPT (tapered thread seal). The FPD can be mounted at any angle, including upside down. For best results, mount directly onto the fuel rail.

FPD-R vs FPD-XR — Which Do I Choose?

Both models have unique base “static” fuel pressure requirements. Base pressure is measured with the fuel pump running and no vacuum line connected to the regulator.

• FPD-R (green top, shorter) — Base static pressure: 40-70 PSI
• FPD-XR (black top, taller) — Base static pressure: 40-105 PSI

Important: The ranges above are base static fuel pressures only. Dynamic fuel pressure created by a rising-rate FPR outside of this range is acceptable, provided the base static pressure is set within the specified range and the vacuum/boost reference line is connected.

Example 1 — Mitsubishi EVO:

• OEM base static fuel pressure: 43.5 PSI
• Boost pressure: 30 PSI
• Rising-rate FPR: Yes
• FPD-R compatible? Yes — base static is within 40-70 PSI. Fuel pressure reaches 73.5 PSI at full boost, but the vacuum/boost reference line must be connected.
• FPD-XR compatible? Yes — vacuum/boost reference line not required as max pressure does not exceed 105 PSI.

Example 2 — BMW E46 M3:

• OEM base static fuel pressure: 72.5 PSI
• Boost pressure: 20 PSI
• Rising-rate FPR: Yes
• FPD-R compatible? No — base static pressure exceeds the 40-70 PSI requirement.
• FPD-XR compatible? Yes — vacuum/boost reference line not required as max pressure does not exceed 105 PSI.

Kit Includes:

• 1x Anodized and laser-engraved aluminium top (R = Range)
• 1x Anodized aluminium body with male threads — 3/8" NPT
• Stainless steel hardware
• 4mm ID rubber vacuum hose
• Vacuum hose Y-fitting

Specifications:

• Model: FPD-R (green top, shorter profile)
• Thread: 3/8" NPT male
• Base static pressure range: 40-70 PSI
• Vacuum/boost reference port: Yes
• Mounting: Any angle, including inverted
• Fuel compatibility: All fuel types including E85 and alcohol blends

Available Part Numbers:

• 20-0178 — FPD-R Fuel Pulse Damper, 3/8" NPT

Why Radium Engineering?

• ✅ Manufactured in the USA to motorsport-grade tolerances
• ✅ CNC-machined anodized aluminium with vacuum/boost reference port for boosted rising-rate FPR applications
• ✅ Trusted by tuners and race teams running high-power builds worldwide
• ✅ Mounts at any angle including inverted — direct fuel rail mounting for best performance
• ✅ Compatible with E85, ethanol, methanol, pump petrol, and flex fuel sensor integration