Overview
ISO 28981:2009 - Mopeds: Methods for setting the running resistance on a chassis dynamometer specifies standardized measurement procedures to determine moped running resistance and to transfer that running resistance to a chassis dynamometer. The standard is applicable to mopeds as defined in ISO 3833 and adapts motorcycle coastdown methods (ISO 11486) to the moped vehicle category. It defines on-road coastdown testing, data processing, and two methods for configuring a chassis dynamometer to replicate real-world running resistance.
Key topics and technical requirements
- Scope and purpose: Measure moped running resistance on the road and set chassis dynamometer load to match that resistance for laboratory testing.
- Two dynamometer-setting methods:
- Derived from on‑road coastdown measurements (coastdown-based calibration).
- Using a running resistance table / fixed load curve with a specific verification procedure.
- Road test conditions:
- Test road must be flat, level, straight, smoothly paved; slope ≤ 0.5% over 2 m.
- Wind and ambient limits: maximum steady wind 3 m/s (gusts 5 m/s); temperature 278–308 K; relative humidity ≤ 95%.
- Standard ambient reference: p = 100 kPa; T = 293 K; air volumetric mass 1.189 kg/m3.
- Coastdown test parameters:
- Use at least four specified speeds including the reference speed(s) to generate a running resistance curve.
- Coastdown speed interval (2Δv): Δv = 5 km/h when reference < 60 km/h, Δv = 10 km/h when ≥ 60 km/h.
- Coastdown starting speed must be > 5 km/h above the measurement start speed to allow settling and power shut-off.
- Measurement accuracy requirements (examples):
- Running resistance force accuracy: ±2%.
- Moped speed: ±1% (resolution 0.45 km/h).
- Coastdown time: 0.01 s resolution; ±0.5% accuracy.
- Chassis dynamometer considerations:
- Inertia mass setting, tyre pressures, warming-up procedures for both dynamometer and moped.
- Verification procedures for dynamometer settings and acceptance criteria.
- Data processing: Calculation and curve fitting of running resistance vs. speed to determine target running resistance at reference speed(s).
Applications and users
ISO 28981:2009 is targeted at:
- Vehicle manufacturers and component suppliers performing moped performance and emissions testing.
- Test laboratories and certification bodies that calibrate chassis dynamometers.
- R&D and type‑approval engineers conducting real-world to laboratory test correlation.
- Regulatory agencies specifying standardized dynamometer settings for compliance testing.
Practical uses include setting dynamometer load curves for emissions, fuel consumption, durability, and performance testing so laboratory results reliably reflect on‑road running resistance.
Related standards
- ISO 3833 - vehicle types, terms and definitions (defines mopeds).
- ISO 7116 - moped measurement method for maximum speed (normative reference).
- ISO 11486:2006 - motorcycle running resistance coastdown methods (basis for ISO 28981 adaptation).
Keywords: ISO 28981:2009, mopeds, running resistance, chassis dynamometer, coastdown test, running resistance curve, reference speed, chassis dynamometer setting.
