Radium Port Injection Kit | 2017+ Honda Civic Type-R (20-0428)

Big-turbo K20C1 builds hit the same wall every time: direct injection runs out of fuel before the engine runs out of air.

The Type-R's DI system is brilliant at stock power and a hard ceiling above it, especially on E85. The Radium Engineering Port Injection Kit for the Honda K20C1 adds the second stage: a PIK adapter plate installs between the intake manifold and cylinder head carrying port injector positions, fed by a custom rail with a large 0.63" internal bore, CNC machined from extruded 6063 aluminum with four 8AN ORB (3/4"-16) ports. Injectors sit at a specific angle ensuring proper spray into the intake ports, phenolic spacers and washers isolate the rail completely from cylinder head heat, and the OEM direct injection system stays untouched underneath. OEM Honda gaskets included.

What You'll Feel

• The K20C1's DI fueling ceiling removed, with port injectors carrying the top end
• A genuine E85 big-power path for FK8 and FL5 builds
• Cooler, more consistent rail temperatures via full phenolic thermal isolation
• Correct atomization from purpose-angled injector positions, not an afterthought spacer
• Stock DI drivability retained at idle and cruise

Features

• PIK adapter plate installs between the intake manifold and cylinder head
• Custom fuel rail: 0.63" internal bore, CNC machined extruded 6063 aluminum, laser etched, 4x 8AN ORB (3/4"-16) ports
• Injector positions machined at a specific angle for proper spray into the intake ports
• Machined phenolic mounting spacers and washers completely isolate the rail from cylinder head heat
• Designed for specific top feed injectors with matching upper and lower O-ring spacing
• Does NOT replace the OEM direct injection system; all fuels including E85; OEM Honda gaskets included

The Details

One packaging note from Radium deserves attention before ordering fittings: the two top fuel rail ports must be plugged with Radium's 14-0150 8AN ORB plugs unless the plastic OEM wiring harness carrier is modified, which leaves the remaining ports carrying feed and accessory duty on unmodified cars. System design is the builder's job, with port injectors (top feed, correct O-ring spacing per Radium's spec), an auxiliary fuel supply, and a controller or ECU strategy for the second stage all selected separately, and the 8AN ORB ports accepting the regulator, damper, and gauge adapters the architecture calls for. The kit's role is the hard part: precision-machined injector geometry, sealed manifold interface, and a rail that will not become the next restriction.

Kit Includes

• 1x PIK adapter plate
• 1x Custom port injection fuel rail (4x 8AN ORB ports)
• Fuel rail mounting hardware with phenolic spacers and washers
• OEM Honda gaskets
• Injectors, fittings, plugs (14-0150), plumbing, and controller NOT included

Applications

• 2017-2021 Honda Civic Type-R FK8 (K20C1)
• 2023+ Honda Civic Type-R FL5 (K20C1)
• Top ports require 14-0150 plugs unless the OEM harness carrier is modified

Feeding the Second Stage

Port injection needs its own regulated supply, and on the FK8 that problem is already solved upstream. The Radium fuel hanger plumbing kit for the 2017-2021 Civic Type-R (20-1085-03 / 20-1085-05) uses a dual fuel pressure regulator with two independent outputs: the black knob regulates the OEM direct injection low pressure feed, and the green knob governs a second regulated outlet that ships plugged from the factory, reserved for exactly this kit. Connecting the two takes an 8AN ORB DFPR adapter fitting and a fuel line.

• Fuel hanger plumbing kit, FK8 (20-1085-03 / 20-1085-05): DFPR, gauge, filter, and full tank-to-firewall plumbing with the port injection outlet built in
• Fuel pump hanger, 2016+ Civic (20-1080 / 20-1082): the in-tank supply supporting one to three aftermarket pumps