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An on-board measurement system that simultaneously measures road traffic, vehicle running conditions and exhaust emissions was installed in a diesel freight vehicle with two tons payload. Actual NOx mass emissions were compared with that measured in a typical test mode for urban cities on a chassis dynamometer. The frequency of vehicle accelerations in actual urban cities was found to exceed that of a typical test mode for urban cities on a chassis dynamometer, which resulted in increased NOx from actual running conditions compared with the typical test mode for urban cities. The dynamics of NOx emissions at an actual roadside was also analyzed. It was observed that NOx emission based on distance with an actual city route test was about two times higher than that of a free way route and a typical test mode for urban cities. The reason for high NOx with the city route was explained by the higher frequency of lower gears at which higher NOx is emitted.

Reduction of particulate emissions from diesel engine is an important theme from the view point of air pollution. Experiments were carried out using a four-stroke single cylinder direct-injection diesel engine. A new method to measure diesel particulates has been developed. Particulates were sampled with a freezing method just behind an exhaust valve and examined through a scanning electron microscope. Shape and structure of particulates and the size distributions are measured under wide operating conditions obtained with above method. The total mass of particulate emissions was measured using a dilution tunnel sampling system. The heat release processes were analyzed using indicator diagrams and the relation between burning condition and particulate emissions were discussed, after systematic experiments under constant revolution speed of 2000 r/min for several load and injection timing conditions.