The multi-cylinder camless engine is a Ricardo-developed in-line three-cylinder camless gasoline direct injection (GDI) research engine. The four independently controlled, hydraulically actuated valves per cylinder allow for research into advanced engine cycles and combustion modes.
This engine was originally commissioned at the Sir Harry Ricardo Laboratories for the 2/4 SIGHT project. It produced the first ever, controlled operating mode switches from four-stroke to two-stroke (and back) and demonstrated outstanding two-stroke performance of 150 Nm/l at 1000 rpm and 230 Nm/l at 2500 rpm thanks to its innovative combustion chamber.
The concept of the 2/4 cycle engine, illustrated below, relies on using the traditional cylinder poppet valves found commonly in four-stroke engines to be used also in two-stroke mode by switching to a different valve opening frequency. Unique valve, fuel and air handling control strategies ensure a smooth mode switch and good scavenging in two-stroke operation. A demonstration of mode switching can be seen in the video below.