ISO 7293:2021

Overview

ISO 7293:2021 - Forestry machinery - Portable chain‑saws - Engine performance and fuel consumption - specifies a laboratory test method to assess the performance and fuel consumption of internal combustion engines that power portable chain‑saws. The third edition (2021, corrected 2022) updates measurement accuracy, test conditions, and the operating procedure for generating power, torque and fuel‑consumption curves for development, certification and comparative benchmarking.

Key topics

• Scope: Method for testing engine brake power, torque and fuel consumption of portable chain‑saw power units.
• Measurement accuracy requirements:
  • Torque ±2% (system calibrated for friction losses)
  • Engine speed ±2%
  • Fuel consumption ±2%
  • Fuel and inlet air temperature ±2 °C
  • Barometric pressure ±100 Pa
• Power correction factor (α):
  • Corrects measured power to defined reference atmospheric conditions (25 °C, dry pressure 99 kPa).
  • α is calculated from test dry atmospheric pressure and inlet air temperature using the standard’s formula (see Clause 5.4).
  • If α falls outside the standard’s allowable limits, corrected values must be reported and test conditions stated.
• Test conditions and preparation:
  • Test the machine with standard production equipment (except saw chain and guide bar).
  • Follow manufacturer’s engine adjustments; disable power‑consuming auxiliaries.
  • Fuel: petrol meeting ISO 5164 knock specification, min octane (R+M)/2 = 87; density 680–790 kg/m3 at 15 °C; two‑stroke engines mixed per manufacturer.
  • Engine mounting and dynamometer coupling requirements; run‑in rules are specified.
• Operating method:
  • Run at full throttle and record brake power, torque and fuel consumption in 300 r/min steps across a range from 900 r/min above peak power down to 900 r/min below peak torque.
  • Readings taken after engine temperature stabilizes (10 s interval once stable).
• Test report content: Manufacturer/model/serial, engine bore/stroke/displacement, fuel density, oil ratio, ambient conditions, measured curves, peak power/torque speeds, specific fuel consumption, and equipment used.

Applications

• Test laboratories performing performance and fuel‑efficiency testing on portable chain‑saw engines.
• Chain‑saw and engine manufacturers for product development, quality control and performance benchmarking.
• Regulatory and safety bodies requiring standardized engine performance data.
• Aftermarket service providers and researchers analyzing specific fuel consumption or optimizing engine tuning.

Related standards

• ISO 5164 - Petroleum products - determination of knock characteristics (referenced for fuel properties)
• ISO 12100 - Safety of machinery - general principles (terms and definitions referenced)

Keywords: ISO 7293:2021, portable chain‑saws, engine performance, fuel consumption, power correction factor, dynamometer test, specific fuel consumption, test method.