Automotive catalytic converter exhaust system

In a vehicular internal combustion engine exhaust system, wherein gases at elevated temperature are exhausted from said engine through an exhaust manifold following combustion and conveyed by said exhaust system from said manifold to the atmosphere, said exhaust system containing a catalytic converter having therein a three-way catalyst through which said gases pass for reduction of their content of unburned hydrocarbons, nitrogen oxides and carbon monoxide, the improvement which comprises:

• (a) conduit means joining said exhaust manifold and said converter and through which said gases are conveyed from said exhaust manifold to said converter, said conduit means retaining sufficient heat in said gases such that said gases upon reaching the inlet of said converter are at a temperature above the minimum operating temperature of said three-way catalyst;
• (b) said conduit means comprising:
• (1) an inner corrugated pipe having an imperforate surface in contact with said exhaust gases;
• (2) an outer corrugated pipe;
• (3) said inner and outer corrugated pipe each being flexible in all directions;
• (4) said inner and outer pipes comprising spirally wound strips of stainless steel;
• (5) said outer pipe spaced a predetermined distance from said inner pipe;
• and
• (6) a flexible refractory fiber thermal insulation in said space between said outer and inner pipes so that there is not contact between said outer and inner pipes;
• and
• (c) attachment means associated with said outer and inner pipes for attaching said conduit means to said exhaust manifold and said catalytic converter.