Internal combustion engines (ICE) are the main sources of powering for almost all road vehicles, yet many other machines too. Being under strength development for a number of years, they have already reached a relatively high level of technical excellence and now they also produce acceptable output parameters. Still, they are not devoid of drawbacks. Harmful exhaust emissions can be pointed as the most important here. This problem is the main focus of interest for automotive researchers and engineers. Continuous decrease of exhaust emission limits additionally intensifies their efforts to produce more green engines and vehicles. On the other hand,.