BS ISO 7293:2021 pdf download – Forestry machinery — Portable chainsaws — Engine performance and fuel consumption
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.
7.2 Procedure 7.2.1 Determination of the peak power and peak torque engine speed Prior to mounting the engine on the power test bench, warm up the engine and, if applicable, set the idle speed adjuster and low speed mixture adjuster for best idling at the rotational frequency recommended by the manufacturer. It is recommended operating the engine at any speed and at approximately 75 % of its expected maximum power. Continue the warm‑up until the engine‑stabilized temperature has been achieved. Run the engine at fully open throttle on the dynamometer bench and determine the engine speed at which the engine makes peak torque and the speed at which it makes peak power. If an adjustment of the fuel/air mixture by the operator is foreseen in the operator’s instructions, adjustment to achieve the peak power is allowed. Record these speeds, as they will be used in determining the power curve in 7.2.2.
7.2.2 Determination of the power curve and fuel consumption curve Prior to the test, record the ambient air temperature (°C) and air pressure (kPa) in Table 1. Run the engine with fully open throttle at the engine speed of peak power plus 900 rpm until engine‑stabilized temperature has been achieved. Record the following readings; power (kW), torque (N∙m), fuel consumption (g/h), enginestabilized temperature (°C), and engine speed (r/min). Repeat by decreasing the engine rpm in steps of 300 r/min until the last step is 900 r/min below the engine speed at peak torque as determined in 7.2.1, and record the information outlined in for every step. If the machine is using a clutch, only record at intervals in which the clutch is transferring all of the power generated by the engine.BS ISO 7293 pdf download.