Engine exhaust gas cleaning system

A catalytic converter for the exhaust gases of an internal combustion engine having an exhaust pipe, said catalytic converter having a converter section formed by a first outer shell, said first outer shell having a tubular section closed at its ends by respective end plates, one of said end plates defining a tubular inlet end extending away from said one end plate for receiving exhaust gases from said exhaust pipe, the other of said end plates defining a tubular outlet end extending away from said other end plate and in an opposite direction from said tubular inlet end for discharging exhaust gases to the atmosphere, and a second outer shell for surrounding and supporting said first outer shell in spaced relation, one end of said second outer shell being formed with an exhaust gas inlet surrounding and spaced from said tubular inlet end and connected to said exhaust pipe, the other end of said second outer shell being in spaced surrounding relation to said tubular outlet end for defining an atmospheric supplementary air inlet of a supplementary air conduit for adding atmospheric air to the exhaust gases flowing through said converter section, said supplementary air conduit having an intermediate portion defined by the outer periphery of said converter section first outer shell and said second outer shell and a discharge end upstream of said converter section within said exhaust gas inlet for flow with the exhaust gases into said tubular inlet end of said converter section.