<div class="htmlview paragraph">This paper describes a research programme to assess the potential of the high speed direct injection diesel engine fitted with unit injectors. A 0.4 litre boosted single cylinder engine with an electronically controlled unit injector was tested to evaluate smoke limited torque, fuel economy, exhaust emissions and combustion noise.</div> <div class="htmlview paragraph">The paper concludes that direct injection engines using electronic unit injectors would be technically viable for small-medium diesel engined vehicles of the 1990's. These would have very competitive performance and fuel economy and be capable of meeting US Federal 1987 emissions limits. However, further noise reduction work is required.</div>