ISO 6855-3:2012

Overview - ISO 6855-3:2012 (moped fuel consumption at constant speed)

ISO 6855-3:2012 specifies standardized methods to measure fuel consumption at a constant speed for mopeds (as defined in ISO 3833) equipped with spark-ignition engines (four‑stroke, two‑stroke or rotary piston). The standard covers both on‑road and chassis dynamometer test procedures and is intended to be used together with ISO 6855-1 (general test requirements). It defines test setup, instrumentation, environmental limits and data presentation for repeatable, comparable moped fuel consumption and gaseous exhaust emissions measurement.

Key topics and technical requirements

• Scope: Applies to mopeds per ISO 3833 with spark‑ignition engines; constant‑speed fuel consumption tests on road or chassis dynamometer.
• Test methods: Road measurement method and chassis dynamometer method (including carbon balance and fuel flowmeter options).
• Rider and mass: Standard rider clothing and position; rider mass 75 kg ± 2 kg and height 1.75 m ± 0.02 m; total test mass (rider + instruments) must be measured.
• Speed control: Target test speed must be maintained within ± 1 km/h; tests typically performed in highest gear unless instability requires a lower gear (gear must be reported).
• Test section and distance: Test section must consume at least 10 mL of fuel or be longer than 300 m; section length measured to 0.1% tolerance.
• Instrumentation: Fuel supply measurement accuracy ± 2%; volumetric systems must monitor fuel temperature; switch over to measuring supply within 0.2 s.
• Ambient and aerodynamic limits: Wind, humidity and temperature constraints (air temperature 278 K–308 K); relative air density must not differ by more than 7.5% from reference conditions.
• Repeatability and data handling: Minimum three tests; average values computed per specified formulas; results presented per Annex B and rounded to one decimal place. Annex A provides an interpolation/determination method when constant‑speed stability is problematic (four‑run method: two below and two above target speed).

Applications and users

• Practical uses: type‑approval testing, regulatory compliance checks, laboratory and field verification of moped fuel efficiency, R&D for engine tuning and vehicle design, comparative fuel consumption studies.
• Typical users: vehicle manufacturers, independent test laboratories, regulatory agencies, certification bodies, academic and applied researchers working on small‑vehicle emissions and fuel economy.
• Test environments: on‑road constant‑speed assessments and controlled chassis dynamometer setups (ISO 28981 guidance for dynamometer resistance settings).

Related standards

• ISO 6855-1:2012 - Measurement methods for gaseous exhaust emissions and fuel consumption - General test requirements
• ISO 28981 - Methods for setting running resistance on a chassis dynamometer
• ISO 7116 - Maximum speed measurement for mopeds
• ISO 3833 - Vehicle category and definitions (moped classification)

Keywords: ISO 6855-3, moped fuel consumption, constant speed test, chassis dynamometer, road test, fuel flowmeter, carbon balance method, gaseous exhaust emissions, ISO 6855-1.