Radium Fuel Rail Plumbing Kit | 1994-2005 Mazda Miata (20-0422/20-0423)

The Radium Miata rail has the ports; this kit is the plug-and-play bridge back to your factory fuel lines.

A bare aftermarket rail leaves you sourcing fittings and hose to meet the OEM system. The Radium Engineering Fuel Rail Plumbing Kit for the 1994-2005 Miata closes that gap with a chassis-specific package for each generation: the 94-97 kit (20-0422) retains the OEM fuel pressure regulator and replaces the feed and return hoses, while the 99-05 kit (20-0423) retains the OEM fuel pulse damper and feed hose. Both bolt to the Radium 20-0369 fuel rail for a factory-clean connection with no custom fabrication. Pick your generation and plumb it once.

What You'll Feel

• A plug-and-play rail install with the OEM lines meeting the Radium rail cleanly
• Factory pressure regulation retained, so the stock fuel map logic stays intact
• Fresh hoses replacing decades-old rubber in the spots this kit renews
• An afternoon install instead of a fitting-sourcing project

Features

• 20-0422 (1994-1997): retains the OEM fuel pressure regulator, replaces the fuel feed and return hoses
• 20-0422 contents: 8AN ORB to 5/16" barb fitting, 8AN ORB to OEM FPR fitting (20-0301), 8AN ORB plug, and Radium 5/16" fuel hose
• 20-0423 (1999-2005): retains the OEM fuel pulse damper and fuel feed hose
• Both designed for the Radium 20-0369 Mazda 1.8L BP fuel rail (sold separately)
• Adapts the rail's 8AN ORB ports to the factory Miata fuel system

The Details

Each generation gets its own logic because Mazda changed the fuel architecture between NA and NB. On 94-97 cars, the return-style system's OEM regulator carries over, with the kit's 20-0301 adapter mating it to the rail's ORB port, the barb fitting and fresh 5/16" hose handling the feed, and the ORB plug closing the unused port. On 99-05 cars, the factory pulse damper stays in service, screwing into the Radium rail through the kit's adapters while the OEM feed hose is reused. One clearance note straight from Radium for the 99-05 kit: if the car is equipped with EGR, it must be removed for the OEM fuel pulse damper to fit. Both kits assume the Radium rail is already on the engine and the rest of the factory fuel system is stock; builds moving to aftermarket regulators or larger feed lines should skip this kit and plumb the rail's 8AN ORB ports directly with Radium adapter fittings instead.

Kit Includes

• 20-0422: 1x 8AN ORB to 5/16" barb fitting, 1x 8AN ORB to OEM FPR fitting, 1x 8AN ORB plug, Radium 5/16" fuel hose
• 20-0423: adapters and hardware to retain the OEM pulse damper and feed hose on the Radium rail

Applications

• 20-0422: 1994-1997 Mazda Miata (1.8L BP) with the Radium 20-0369 fuel rail
• 20-0423: 1999-2005 Mazda MX-5 Miata (1.8L BP) with the Radium 20-0369 fuel rail; EGR removal required for OEM damper fitment if equipped