Radium FPD-R/FPD-XR Inline Fuel Pulse Damper Kit

Radium FPD-R / FPD-XR Inline Fuel Pulse Damper Kit

Injector opening and closing creates pressure pulses in the fuel rail that can cause unstable fuel pressure, idle surge, and erratic lean AFR spikes (“stumbling”) that are difficult to tune out. The Radium Engineering Inline Fuel Pulse Damper absorbs these oscillating pulses via an internal diaphragm, stabilising fuel pressure throughout the RPM range. Particularly effective with high-flow injectors and boosted applications using a 1:1 rising-rate FPR.

Radium FPDs feature a vacuum/boost reference port — essential for boosted systems running a rising-rate FPR, ensuring correct damper performance at elevated fuel pressures. Compatible with all fuel types including E85 and methanol.

FPD-R vs FPD-XR — Which to Choose?

FPD-R (Range) — Green top, 1.98" tall

• Base static fuel pressure requirement: 40-70 PSI
• Compact size — ideal for space-constrained applications
• Vacuum/boost reference line required for boosted applications exceeding 70 PSI dynamic pressure

FPD-XR (Extra Range) — Black top, 2.60" tall

• Base static fuel pressure requirement: 40-105 PSI
• Wider response range — Radium recommends the FPD-XR if space permits
• Vacuum/boost reference line not required if maximum fuel pressure does not exceed 105 PSI

Note: Base pressure = fuel pressure measured with the pump running and NO vacuum line connected to the regulator. Dynamic pressure from a rising-rate FPR outside these ranges is acceptable provided the base static pressure is set within the specified range and the vacuum/boost reference line is connected.

Selection Examples

Mitsubishi Evo — 43.5 PSI base, 30 PSI boost, rising-rate FPR: Both FPD-R and FPD-XR are suitable. FPD-R requires vacuum/boost reference line connected.

BMW E46 M3 — 72.5 PSI base, 20 PSI boost, rising-rate FPR: FPD-R not suitable (base exceeds 70 PSI). FPD-XR required.

Variant & Part Number Guide

Specifications

• Housing: Anodised aluminium, 0.69" centre bore
• Ports: 3/4"-16 UNF (8AN ORB) inline inlet/outlet
• Sensor port: 1/8" NPT female — for fuel pressure gauge or sensor
• Mounting: M6 bolts/nuts — mountable at any angle including inverted
• Diaphragm: Gasoline and alcohol (E85) resistant
• Seals: Viton O-rings

Kit Includes

• Anodised/laser engraved aluminium top (R = green, XR = black)
• Anodised aluminium body with female 8AN ORB ports
• Anodised aluminium ORB adapter fittings (per variant selection)
• Gasoline and alcohol (E85) resistant diaphragm
• Stainless steel M6 mounting bolts and nuts
• 4mm ID rubber vacuum hose
• Vacuum hose Y-fitting
• 1/8" NPT plug

Why Radium Engineering?

• ✅ Manufactured in the USA to motorsport-grade tolerances
• ✅ CNC-machined billet aluminium components built for performance and longevity
• ✅ Trusted by high-power build tuners and race teams worldwide
• ✅ Vacuum/boost referenced — correct performance at elevated fuel pressures on boosted builds
• ✅ Compatible with E85, pump petrol, methanol, and all exotic fuel types