Method for controlling fresh air supply to the exhaust system of an internal combustion engine

The method involves injecting fresh air into an exhaust during cold start phase of an internal combustion engine and expansion phase. An exhaust valve (34) is opened when pressure in a combustion chamber (18) is lower than pressure prevailing at the exhaust to feed the fresh air from the exhaust into exhaust gas present in the combustion chamber. The fresh air is injected into an exhaust pipe (32) and an exhaust manifold (42) of an exhaust line (40).