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Fuel consumption and exhaust gas emission regulations are being tightened around the world year by year. Electric vehicles are needed to reduce carbon dioxide emissions. Especially, Plug-in hybrid heavy-duty vehicles (PHEVs) are expected to become widespread. PHEVs enable all-electric modes, as well as hybrid modes, using both engines and electric motors, but the control system significantly affects the characteristics of fuel consumption and gas emission. In this study, we used new testing machine (we call extended HILS) to analyze the fuel consumption and gas emission for different plug-in hybrid control systems and investigated the optimal control method for PHEVs.

Study of DME diesel engines was conducted to improve fuel consumption and emissions of its. Additionally, DME trucks were built for the promotion and the road tests of these trucks were executed on EFV21 project. In this paper, results of diesel engine tests and DME truck driving tests are presented. As for DME diesel engines, the performance of a DME turbocharged diesel engine with LPL-EGR was evaluated and the influence of the compression ratio was also explored. As for DME trucks, a 100,000km road test was conducted on a DME light duty truck. After the road test, the engine was disassembled for investigation. Furthermore, two DME medium duty trucks have been developed and are now the undergoing practical road testing in each area of two transportation companies in Japan.

Next-generation vehicles which include Electric Vehicles and Hybrid Electric Vehicles are studied and expected to reduce carbon dioxide emissions. The number of small delivery hybrid trucks has increased in the commercial vehicle class. The engine load of a commercial hybrid truck is reduced by using an electric motor. Fuel economy of the hybrid truck is improved with the assist. On the other hand, exhaust-gas temperature is decreased, and it has a negative effect on the purification performance of aftertreatment system. In this report, the fuel performance and emission gas characteristics of marketed small hybrid trucks were surveyed using the chassis dynamometer test system.

In the conventional approval test method of fuel consumption for heavy-duty diesel vehicles currently in use in Japan, the fuel consumption under the transient test cycle is calculated by integrating the instantaneous fuel consumption rate referred from a look-up table of fuel consumptions measured under the steady state conditions of the engine. Therefore, the transient engine performance is not considered in this conventional method. In this study, a highly accurate test method for fuel consumption in which the map-based fuel consumption rate is corrected using the transient characteristics of individual engines was developed. The method and its applicability for a heavy-duty diesel engine that complied with the Japanese 2009 emission regulation were validated.