ISO 22561:2020

ISO 22561:2020 - Overview

ISO 22561:2020 defines the dimensional and installation requirements for fuel injectors used in gasoline direct injection (GDI) engines. The standard specifies the geometry, tolerances and interfaces needed to mount injectors into the cylinder head and to connect them to the fuel rail injector cup. It also describes the injector cup interface within the rail and key sealing features (seal ring and O‑ring). Note: GDI systems typically operate at pressures up to about 35 MPa.

Key topics and technical requirements

• Scope and purpose: Standardizes the physical interface and integration of GDI fuel injectors to ensure reliable sealing, positioning and serviceability across engine and injector designs.
• Injector types: Two nozzle-diameter types are defined (Type A: 6.0 mm; Type B: 7.5 mm).
• Mounting concept: Injectors are not rigidly fastened to the head; they are located by the fuel rail using spring force and rail pressure. An adaptor between injector and cylinder head is recommended to accommodate misalignment and provide vibration/noise insulation.
• Sealing features: Primary sealing is by a nozzle seal ring against combustion pressure and an O‑ring at the injector fuel inlet.
• Critical geometries: Dimensions and tolerances for injector body, nozzle bore, injector cup (rail), and cylinder head bore are specified, including:
  • Injector cup bore diameters (examples): 9.4 ± 0.025 mm (Option 1) and 10.7 ± 0.025 mm (Option 2).
  • Cylinder head nozzle bores (examples): 6.25 H8 or 7.75 H8 options depending on injector type.
  • Surface finish and taper requirements (Rz roughness, insertion taper angles, radii).
• Geometric tolerances: Requirements for cylindricity, coaxiality, perpendicularity, parallelism and flatness to ensure sealing under thermal and pressure conditions.
• High‑pressure connector: The rail connector must comply with ISO 18418‑1 or ISO 2974.

Practical applications and users

• Who uses it: Engine OEMs, fuel injector manufacturers, fuel-rail suppliers, powertrain design engineers, test laboratories and suppliers of engine cylinder heads and adaptors.
• Why it matters:
  • Ensures interchangeability and reliable sealing between injectors, adaptors, cylinder heads and fuel rails.
  • Reduces design iterations by providing agreed interface dimensions and tolerances.
  • Aids compliance with high‑pressure fuel system safety and durability expectations in GDI engines.
• Use cases: Component design and validation, supplier agreements, CAD and assembly specification, manufacturing inspection criteria and service/replacement compatibility checks.

Related standards

• ISO 18418‑1 - Medium pressure liquid fuel supply connections (60° female cone connectors)
• ISO 2974 - 60° female cones for high‑pressure fuel injection components

Keywords: ISO 22561:2020, GDI engines, fuel injector installation, injector cup, fuel rail, cylinder head bore, injector adaptor, dimensions and tolerances, high‑pressure connector.