Determining the tendency of a petrol with or without additives to form deposits in an engine involves injecting petrol across a tube held at a constant temperature and determining the amount of deposit formed by weighing the tube

摘要

Laboratory method for evaluating the tendency of a petrol or petrol with additive to form deposits while the engine is running, by placing a tube in the injector oven of a gas chromatograph; keeping the tube at constant temperature in a constant air flow; injecting the petrol across the tube, and determining the amount of deposit formed by weighing the tube after dismounting it The tube is a glass insert with a mixing chamber. The petrol is injected by a pump across a needle positioned so the injection is at about 10 mm inside the tube. The petrol is injected at a constant flow of 0.5 to 2 kg/24 hours, preferably around 1 kg/24 hours. The petrol to be tested has 15 to 25% by mass (preferably 20%) of the lightest fractions removed before injection by sweeping with an inert gas at ambient temperature. To determine the tendency to form deposits on the inlet valves to the engine, the temperature is kept constant at between 250 and 300 deg. C, preferably near 275 deg. C. To determine the tendency to form deposits in the combustion chamber, the temperature is kept constant at between 325 and 375 deg. C, preferably near 350 deg. C.