Traffic engineering

6.1      Otto engines6.2      Otto gas engines
6.3      Diesel engines6.4      Diesel gas engines
6.5      Stirling motors6.6      Multi-fuel engines
6.7      Rotary piston engines6.8      Engines for other fuels 
6.9      Research and experimental engines6.10     Small gas turbines
6.11    Power generating sets driven by internal combustion engines6.12     Parts and Accessories for internal combustion engines
6.13    Heat exchangers