In order to gain better control over the combustion process, a new type of injection concept was introduced in a previous paper by the author and co-workers . Rotating the injector in a DI diesel engine is a powerful way for the engine developer to influence the fuel-distribution within the combustion chamber.The rotating injector has in this work been implemented onto a modern 4-valve engine. The injector has speed capability up to 10,000 rpm in both directions by the use of an electric motor drive. The power requirement is modest. Typically up to 50 W.The tests reveal that the rotating injector strongly affects the combustion and formation of emissions. For each loadpoint an optimum injector speed exists, where maximum reduction of smoke and CO can be obtained. Among the tested loadpoints, smoke could be reduced by up to 74 % by rotating the injector counter-swirl at 3350 rpm. This was attributed to reduced flow stagnation onto the piston bowl wall and more efficient air-fuel mixing which also reduced the ignition delay and intensified the combustion. The impact on NO was smaller (+16%) and showed an opposite behavior to soot.A relationship with the effective swirl ratio at TDC is anticipated for co-swirl rotation.An optical study of spray development shows that when the injector speed is so high that the sprays start interacting, a toroidial fuel cloud is formed.