A fuel injector was mounted in the cylinder wall of an engine of 60 ccm displacement. A small prechamber, through which the fuel was injected into the cylinder space, was introduced. The influence of the shape and dimensions of the prechamber, and the influence of an air stream or a stream of combustion products through it, and the fuel spray was examined. The penetration and atomisation of the sprays were observed. Two of the most promising arrangements regarding fuel consumption and pollution were investigated in detail. The omission of fuel injection at partial engine loads was also examined, and the electronic control of fuel injection was studied. The results of these laboratory investigations are presented.