Method of reducing the NO.sub.x emission of a supercharged piston-type internal combustion engine

A method of reducing NO.sub.x emissions of a turbocharged internal combustion engine having an exhaust conduit guiding an exhaust gas stream, a charge-air intake conduit guiding a charge-air stream and a turbocharger including a turbine disposed in the exhaust conduit and a compressor disposed in the charge-air intake conduit;

• comprising the steps of
• (a) branching off, by a controlled operation of a valve, a partial exhaust gas quantity from the exhaust gas stream of at least one predetermined engine cylinder upstream of the turbine as viewed in a direction of exhaust gas flow;
• (b) passing the partial exhaust gas quantity through a particle filter in a zone where step (a) is performed;
• (c) introducing the partial exhaust gas quantity into the charge-air stream upstream of the compressor;
• and
• (d) heating the particle filter by at least one part of the exhaust gas stream.