<div class="htmlview paragraph">Very high mean effective pressures can be obtained from the diesel engine with limited maximum cylinder pressures by using a large clearance volume, that is, a low compression ratio, at high loads. The resultant low compression temperature is an added advantage as far as power production is concerned, but gives rise to excessive ignition delay and hence uncontrolled combustion.</div> <div class="htmlview paragraph">This problem was studied in a single-cylinder four-stroke engine. Various methods of controlling combustion rate were found. The best combination of factors resulted in exceptionally smooth combustion and quiet running at a load of 400 psi bmep, using a compression ratio of 8:1, which gave a maximum pressure of only 1600 psi. Metal temperatures were well within the limits of normal usage. The low percentage heat and friction losses resulted in quite moderate rates of fuel consumption in spite of the low expansion ratio.</div>