ISO 7293:2021 pdf – Forestry machinery — Portable chain- saws — Engine performance and fuel consumption.
1 Scope This document specifies a method for testing the performance and fuel consumption of internal combustion engines used to power portable chain-saws. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 5164, Petroleum products — Determination of knock characteristics of motor fuels — Research method ISO 12100, Safety of machinery — General principles for design — Risk assessment and risk reduction 3? Terms? and? definitions For the purposes of this document, the terms and definitions given in ISO 12100 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: — ISO Online browsing platform: available at https:// www .org/ obp — IEC Electropedia: available at http:// www .electropedia .org/ 4 Accuracy of measurements 4.1 Torque: ±2 % of measured torque. The torque measuring system shall be calibrated to take friction losses into account. 4.2 Engine speed: ±2 % of measured speed. 4.3 Fuel consumption: ±2 % of measured consumption. 4.4 Fuel temperature: ±2 °C. 4.5 Engine inlet air temperature: ±2 °C. 4.6 Barometric pressure: ±100 Pa.
6 Conditions of measurement 6.1 Measurements shall be carried out on a chain-saw with its standard equipment. 6.2 The machine shall be complete (except saw chain and guide bar) with all standard production auxiliaries for its operation (filter, silencer, cooling system, etc.). 6.3 The engine shall be adjusted according to the manufacturer’s recommendations as stated in the operator’s instructions for normal operating conditions. If an adjustment of the fuel/air mixture by the operator is foreseen in the instructions, an according adjustment to achieve the maximum possible power is allowed. 6.4 Power-consuming auxiliaries (for example, electrical handle heating) shall be turned off. 6.5 No extra cooling on the engine or air supply is allowed. 6.6 The fixture used to mount the engine to the dynamometer should be verified that it does not influence the performance on the unit compared to an “in-use” condition. 6.7 The engine shall be coupled to the brake power test bench in such a manner that the engine crankshaft is aligned with the brake shaft and connected to it with a flexible coupling. The use of the engine clutch is optional. 6.8 A new engine shall be run in, in accordance with the manufacturer’s instructions. If the engine was previously run in, this operation shall be omitted. 6.9 The fuel shall consist of petrol with a minimum octane (R+M)/2 of 87, measured according to ISO 5164, and, if it is a two-stroke engine, mixed with two-stroke oil according to the manufacturer’s recommendation. The density of the fuel shall be 680 kg/m 3 to 790 kg/m 3 at 15 °C.
7 Operating method 7.1 General With the throttle in the fully open position, record the brake power, torque and fuel consumption as a function of the rotational frequency in steps of 300 r/min, starting from 900 r/min above peak power speed and decreasing down to 900 r/min below the peak torque speed. Take the readings during the 10 s interval after the temperature has stabilized at each step, Table 1 shows an example of how to record the data at each step. The engine temperature is stable when the engine coolant, block or head absolute temperature has settled within ±3 °C for at least 30 s. Take the readings at least over a rotational frequency range limited by the rotational frequency for maximum torque minus 900 r/min, and the rotational frequency for maximum power plus 900 r/min. If the engine speed is limited below the speed of maximum power plus 900 r/min, measure at the maximum speed achievable. If the engine does not run with a stable speed, carry out the test at the maximum possible stable speed. This speed shall however not be more than 480 r/min below the maximum achievable speed. ISO 7293:2021(E)