抄録
The effect of oil diluted with fuel on unburned hydrocarbon (HC) emission from a spark ignition engine was studied. The weight of the oil and fuel (gasoline) was measured, respectively, and they were mixed to obtain oil with a fixed level of dilution. This diluted oil was then supplied to the oil pan of a single cylinder engine. It was observed that when the engine was firing, the diluted oil had no influence on HC emissions in the exhaust. However, during motoring, the HC concentration increased proportional to the fuel concentration in the oil. Therefore, the behavior of the HC concentration in the exhaust was investigated in the deacceleration process. First, the engine was operated in the firing mode. Then, the fuel supply to the engine was cut, putting it in the motoring mode. It was found that most of the exhaust HC just after the fuel is cut, comes from film fuel on the surface of the intake pipe and port walls, but that this decreases rapidly while HC from the fuel mixed in the oil increases gradually.
