Overview
ISO 21755-2:2020 specifies a laboratory permeation test procedure to measure evaporative emissions from motorcycles. It applies to motorcycles with liquid fuel tanks and spark‑ignition engines (four‑stroke, two‑stroke or rotary). The standard defines how to precondition, test and report fuel tank and fuel‑line permeation losses and includes an optional permeability procedure for non‑metallic tanks.
Key topics and technical requirements
- Scope: Measurement method for evaporative emissions using a permeation test; includes fuel tanks and fuel line assemblies.
- Preconditioning (fuel soak): Fill with reference/test fuel and soak at 301.2 K ± 5.0 K for 20 weeks (or 316.2 K ± 5.0 K for 10 weeks for a shortened procedure).
- Permeation test procedure:
- Weigh the sealed tank within 8 hours of filling; place in a ventilated, temperature‑controlled enclosure.
- Maintain test temperature 301.2 K ± 5.0 K for 14 days (extend up to 28 days if needed).
- Record weights (if different fuels were used, measure on five separate days per week).
- Calculate permeation as mass loss divided by internal surface area (mg/m2) and then as (mg/m2)/day; round to an integer.
- Linearity requirement: regression r ≥ 0.8 for weight vs test days (otherwise test is void).
- Deterioration factor (DF): Determine DF by ratio of final to baseline permeation or use a fixed DF as regulated locally; apply DF to measured results.
- Durability testing (for tank and fuel‑line assemblies):
- Pressure cycling: 10 000 cycles between 115.1 kPa and 97.9 kPa at 60 s/cycle.
- UV exposure: ≥450 h at ≥24 W/m2 (or equivalent natural sunlight).
- Slosh testing: fill to 40% capacity, rock at 15 cycles/min to 1 000 000 cycles, ±15° angle, at 301.2 K ± 5.0 K.
- Repeat permeation test after durability procedures.
- Fuel line assembly tests: physical and durability tests similar to tanks; connections plugged and clamps tightened to production torque.
- Optional permeability test for non‑metallic tanks: Annex A - test at 313.2 K ± 2.0 K, with specific fill, oven soak and an 8‑week measurement period.
Applications and who uses it
- Motorcycle manufacturers: validate fuel system designs against evaporative emission targets.
- Fuel tank and hose suppliers: characterize material permeation and durability.
- Test laboratories & certification bodies: perform standardized permeation testing for compliance and type‑approval.
- Regulatory authorities: reference method for enforcing evaporative emissions requirements.
Keywords: ISO 21755-2:2020, motorcycle evaporative emissions, permeation test, fuel tank permeability, fuel line assembly, durability testing, permeation rate.
Related standards
- Other parts of the ISO 21755 series and guidance from ISO/TC 22 (Road vehicles) are relevant. National or regional evaporative emissions regulations and laboratory standards should be consulted alongside ISO 21755-2:2020 for compliance and implementation.