Overview
ISO 9249:2007 - "Earth‑moving machinery - Engine test code - Net power" specifies a standardized method to determine and report the net power of reciprocating internal combustion engines used to propel earth‑moving machinery (see ISO 6165). It defines how to measure engine power at the crankshaft (or equivalent) with specified equipment and auxiliaries fitted or deducted, ensuring consistent, comparable engine net power ratings for manufacturers, test laboratories and end users.
Key topics and requirements
- Scope and engine types: Applies to RIC spark‑ or compression‑ignition engines (excluding free‑piston engines) and rotary piston engines, naturally aspirated or pressure‑charged (mechanical charger or turbocharger).
- Test method: Uses test method 2 from ISO 15550:2002 (engine power measurement core standard). Standard reference conditions and power correction follow ISO 15550.
- Net power definition: Power measured at the crankshaft with the equipment and auxiliaries specified in ISO 15550 (fans, pumps, compressors etc.) fitted or deducted as required.
- Equipment and deductions:
- Install auxiliaries per ISO 15550 Table 1. If the fan system is not fitted, fan power at 25 °C must be determined and subtracted.
- Other accessories necessary only for machine operation should be removed; if not removable their unloaded power is measured and added back to the engine power.
- Calculation of deductions (fan/pump power) is permitted as an alternative to physical testing, provided accuracy requirements are met.
- Power correction and conditions: Correct measured power to standard atmospheric conditions per ISO 15550 Clause 7. Air‑conditioned test rooms and automatic inlet‑air temperature controls are covered.
- Reporting and accuracy:
- Test reports must include pressures, temperatures, fuel delivery, inlet depression, exhaust back‑pressure and additional data per ISO 15550 and ISO 9249 Table 1.
- Measurement accuracy: measured power may differ from declared power by ±2% or 0.3 kW (whichever greater) at declared speed; ±4% at other speeds.
Applications and who uses it
ISO 9249 is used to:
- Provide consistent net power ratings for earth‑moving machinery specifications and marketing.
- Support engine and machine manufacturers (OEMs) in declaring engine performance.
- Guide test laboratories and certification bodies conducting engine power tests.
- Help fleet managers, equipment purchasers and specifiers compare machines on a like‑for‑like basis.
- Integrate with emissions and performance testing programs (see Annex A on using ISO 14396 results to derive net power).
Related standards
- ISO 15550 - Core requirements for engine power measurement and power correction.
- ISO 14396 - Engine power determination for exhaust emission tests (methods to derive net power from ISO 14396 results are described in Annex A).
- ISO 6165 - Earth‑moving machinery terminology and machine types.
- ISO 8178 - Exhaust emission measurement (related testing contexts).
Keywords: ISO 9249, net power, earth‑moving machinery, engine test code, engine testing, power correction, ISO 15550, ISO 14396.
