Abstract: This is concerned with a method of operating a dual-fuel engine, meaning an engine that is supplied with a mixture of gaseous fuel and air which is ignited by an injection of a small amount of so-called pilot oil which is diesel fuel. Additionally the invention is concerned with a method of operation that injects an approximately constant amount of pilot oil regardless of speed variations so as to save fuel at the higher speeds and is specifically applicable or useful with over-the road dual fuel engines, meaning mobile units on trucks, tractors, etc.

Abstract: This is a dual fuel engine, meaning an engine that is operated with straight diesel fuel or with gaseous fuel and pilot injection of diesel fuel, the invention is primarily concerned with dual fuel engines for use in over-the-road vehicles but it has other applications. The invention also contemplates using the heat from the cooling water of the jackets of the engine to vaporize a liquid fuel into a gaseous state which is thereafter injected directly into the cylinders of the engine during operation on the dual fuel cycle.