BS ISO 8893:2021 pdf download – Forestry machinery — Portable brushcutters and grass-trimmers — Engine performance and fuel consumption 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. 5 Power correction factors 5.1? Definition The power correction factor is the coefficient to determine the engine power under the reference atmospheric conditions specified in 5.2. It can be calculated using Formula (1): the operator is foreseen in the instructions, an according adjustment to achieve the maximum possible power is allowed. 6.4 Power-consuming auxiliaries shall be turned off. 6.5 No extra engine cooling 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 The 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 a 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 is 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...
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