Approaches to low emission levels for a light-duty diesel vehicle were studied according to the 1975 FTP using a Toyota Land Cruiser which is in the 4,000 lb inertia weight class, equipped with a Toyota model B diesel engine, 4-stroke, 4-cylinder and 3-liter displacement with a swirl chamber. A simulation method, which is based on an emission map measured in steady state, was developed and proven to be very useful for an efficient study on the effects of various vehicle design factors. The attainable emission levels of smaller diesel passenger cars were also estimated using this method.
It is concluded that the primary target of HC 0.41, CO 3.4, NOx 1.0 g/mile could be achieved by engine modifications and appropriate transmission and final gear ratio choice for the 4,000 lb class vehicle with some penalty in power and fuel economy. However, the ultimate target of HC 0.41, CO 3.4, NOx 0.4 g/mile is impossible to be achieved for the 4,000 lb class vehicle and very difficult for smaller passenger cars, even if an EGR system and an oxidation catalyst are adopted.