Inertia charge intake manifold for multi-cylinder internal combustion engine and connecting method for branch pipes of intake manifold

A method of connecting an end of a branch pipe of an intake manifold to another member of the intake manifold, the branch pipe and said another member being made of a hard thermoplastic synthetic resin, the method comprising the steps of:

• providing the end of the branch pipe with a flat end surface which is generally perpendicular to an axis of the end of the branch pipe;
• providing said another member with a connecting surface for fixing the flat end surface;
• forming a ring-shaped protrusion on at least one of the flat end surface and the connecting surface;
• arranging a heating wire around the ring-shaped protrusion;
• causing the flat end surface and the connecting surface to be pressed against each other;
• and
• applying a voltage across the heating wire.

A method of connecting an end of a branch pipe of an intake manifold to another member of the intake manifold, the branch pipe and said another member being made of a hard thermoplastic synthetic resin, the method comprising the steps of:

• providing said another member with a connecting bore;
• providing the end of the branch pipe with a cylindrical protrusion to be inserted into the connecting bore and with a brim integral with the cylindrical protrusion;
• arranging a heating wire circumferentially of the connecting bore;
• inserting the cylindrical protrusion into the connecting bore so that the heating wire is located adjacent to a boundary between the cylindrical protrusion and the brim of the branch pipe;
• causing the brim of the branch pipe and said another member to be pressed against each other;
• and
• applying a voltage across the heating wire.