Hybrid exhaust manifold

A hybrid exhaust manifold for an engine having a plurality of cylinders which are operative to generate exhaust gases, said manifold comprising:

• a generally planar inlet flange formed from a metal plate and including a plurality of mounting apertures for mounting the inlet flange on the engine, said inlet flange including a plurality of exhaust ports extending therethrough, each said exhaust port being generally in register with at least one of said cylinders when said inlet flange is mounted on the engine;
• a generally planar stamped formed sheet metal inner shell including an inlet aperture for each said exhaust port, each said inlet aperture being substantially the same size and configuration as the corresponding exhaust port, said inner shell being fixedly attached to said inlet flange such that each said inlet aperture is adjacent and in register with the corresponding exhaust port, each said inlet aperture being defined by a mounting flange stamp formed in said inner shell and extending generally normal to the plane of said inner shell to telescopingly engage the inlet flange at the corresponding exhaust port;
• a stamp formed sheet metal outer shell fixedly attached to said inner shell by a seam weld lying substantially in the plane of the inner shell, said inner and outer shells being configured to define an exhaust chamber therebetween, said outer shell including an outlet aperture extending therethrough and being defined by a tube mounting flange;
• and
• an outlet tube telescopingly engaging and fixedly attached to the tube mounting flange of said outer shell, whereby when said inlet flange is mounted on the engine, exhaust gases generated by the cylinders enter the exhaust chamber through said inlet apertures and exit the exhaust chamber through the outlet aperture and outlet tube.

A hybrid exhaust manifold for an engine having a plurality of cylinders which are operative to generate exhaust gases, said manifold comprising:

• a generally planar inlet flange adapted to be mounted on the engine and having at least one exhaust port extending therethrough, said exhaust port being generally in register with at least one of said cylinders when said inlet flange is mounted on the engine;
• a stamp formed sheet metal inner shell including an inlet aperture for each said exhaust port, said inlet aperture being substantially the same size and configuration as the corresponding exhaust port, said inner shell being fixedly attached to said inlet flange such that said inlet aperture is in register with and adjacent the corresponding exhaust port;
• a stamp formed sheet metal outer shell fixedly attached to said inner shell, said inner and outer shells being configured to define an exhaust chamber therebetween, said outer shell including an outlet aperture extending therethrough and a plurality of stamp formed stiffening ribs to minimize vibrations caused by operation of the engine;
• and
• an outlet tube fixedly attached to said outer shell adjacent said outlet aperture, whereby when said inlet flange is mounted on the engine, exhaust gases generated by the cylinders enter the exhaust chamber through the inlet aperture and exit the exhaust chamber through the outlet aperture and outlet tube.

A method for manufacturing a hybrid exhaust manifold for an engine having a plurality of cylinders which are operative to generate exhaust gases, said method comprising:

• providing a planar metallic inlet flange, first and second sheets of metal and an outlet tube;
• forming at least one exhaust port extending through the inlet flange, said exhaust port being positioned to be placed in registration with at least one of said cylinders;
• stamp forming the first sheet of metal to define an inner shell having an inlet aperture for each said exhaust port and having a mounting flange substantially surrounding said inlet aperture;
• stamp forming the second sheet of metal to define an outer shell having an outlet aperture extending therethrough, the stamp forming of said first and second sheets of metal being such that said inner and outer shells are matable to define an exhaust chamber therebetween;
• mounting the inner shell to the inlet flange with each said mounting flange telescopingly engaging the corresponding exhaust port;
• welding each said mounting flange to said inlet flange at the corresponding exhaust port;
• welding said outer shell to said inner shell to form the exhaust chamber therebetween;
• and
• welding the outlet tube to the outer shell adjacent the outlet aperture therein.