Diesel fuel engines are used widely in a large array of applications such as transport, heavy machinery or power generation and form a significant component of much equipment in agriculture, mining, construction, and freight and passenger transport. The recent significant rise in the price of diesel fuels has added to the importance of maintaining diesel fuel engine equipment so as to allow them to operate as efficiently as possible. Relatively small efficiency gains can lead to a dramatic decrease in fuel consumption and equipment wear, together with corresponding reductions in pollution and other emissions.
It is known that a combustible gas can be added to a diesel fuel engine air intake. The mixture of the combustible gas with the conventional air intake enhances combustion conditions within the cylinder so as to increase efficiency of the diesel fuel combustion process. In the prior art, a combustible gas source, for example an LPG source, is connected to an air inlet of a diesel fuel engine and injected by means of a solenoid valve, at some predetermined rate. This is drawn into the engine air intake stream and mixed in a venturi. The suction of the venturi is provided by the manifold vacuum or pressure difference.
Unfortunately, simple factors in engine performance deterioration significantly reduce the efficiency of the combustible gas injection and hence engine combustion. For example, as the diesel engine is operated, its air filter will naturally reduce the flow rate it allows into the engine air intake streams. As a result, the level of the combustible gas injected is not decreased proportionally. As a further result, the prior art start to decrease in any delivered efficiency gains and, depending on the deterioration of engine components such as the air filter, can do more harm than good by providing conditions in which the engine efficiency is lower with a combustible gas injection than without.