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Toyota Motor Corporation has developed a dedicated compressed natural gas (CNG) powered vehicle “Camry” sedan to achieve near zero emissions and to meet rising demand for alternative fuel. A new engine that uses CNG as fuel has been developed by modifying the base 2.2 liter gasoline engine. In the unmodified base engine, torque and power for CNG decrease compared to gasoline. The new engine has adopted a high compression ratio, intake valves with early closed timing, intake and exhaust valves with increased lift and a low back pressure muffler, which thereby restored the loss of engine power. In order to greatly reduce exhaust emissions, a multi port injection system was chosen, and the injectors and pressure regulator have been newly developed. At the same time, precise A/F ratio control and special catalysts for CNG exhaust gas have been utilized.

The change of the fuel flow rate in an injector with mileage accumulation causes poor drivability and exhaust emission deterioration in Otto-type methanol fueled vehicles with a multi-point fuel injection system. This is one of the serious problems which needs to be solved for the practical use of methanol fueled vehicles. The investigation results reveal that the wear of contact surfaces between a valve needle and a valve body increases the resistance force for valve needle movement and causes the change of dynamic fuel flow rate in the injector. The effects of several countermeasures to solve this problem are evaluated.

The effects of fuel properties and emission control systems on exhaust hydrocarbon emissions have been studied. Using fourteen fuels with different properties, exhaust hydrocarbon emissions were measured for the two vehicle types with different emission control systems, under body catalyst and closed coupled catalyst, under the Federal Test Procedure. The fuel properties included high and low concentrations of olefins and aromatics as well as high and low T90. In addition, two fuels contained MTBE. The hydrocarbon emissions were discussed from the view point of the ozone reactivity and ozone formation potential. The results show that the high ozone reactivity of exhaust emissions are mainly caused by the olefins and aromatics in fuels. And also, the effects of fuel property change on exhaust emissions for the vehicle with an under body catalyst are more sensitive than the case of the vehicle with a closed coupled catalyst.

Special test methods under low temperature, low speed, and moderate temperature, moderate speed operating conditions were devised to evaluate the anti-wear properties of engine oils upon the engine valve train. Many commercial and some test oils were utilized to determine the factors affecting valve train wear. Test results indicate that the low temperature and low speed test conditions were the more severe for the valve train. No simple correlation was found between the concentration of Zn-DTP and valve train wear, however, the influence of dispersant-detergent additives was found to be significant. The chemistry of such additives showed different tappet scuffing characteristics.