With much higher pressures and high technology injectors, present-day diesel engines use the so-called solid injection system applied by Herbert Akroyd Stuart for his hot bulb engine.

In 1996 the horizontal vessel was replaced with a water-cooled refractory lined vertical vessel and the bottom tuyeres replaced with water-cooled top lances for solids injection.

They had the advantage of comparative simplicity, since they did not require the air compressor used by early Diesel engines; fuel was injected mechanically (solid injection) near the start of the compression stroke, at a much lower pressure than that of Diesel engines.