1.  Technical Field
The invention generally relates to an apparatus for heating the air/fuel mixture entering the cylinders of an internal combustion engine.  More particularly, the invention relates to an electric heater adapted for mounting within the air intake system of an engine. 
2.  Discussion
The air/fuel mixture entering the cylinders of an internal combustion engine is commonly heated to increase fuel economy and responsiveness to starting as well as to decrease pollutant discharge.  These intake heating devices generally include a heating element disposed in the intake air passageway of an engine and electrically connected to a power source.  Current is passed through the heating element or coil to increase the temperature of the air as it passes the heating element and into the air intake manifold. 
While the aforementioned heaters generally address cold starting and fuel economy issues, other concerns remain.  A major concern of original equipment manufacturers is product proliferation.  For example, engines equipped with existing heater designs typically require an intake housing different from that of an engine not equipped with a heater.  In addition, the heater configuration and dimensions may need to be varied for vehicles with a 24 volt system instead of a 12 volt system.  Due to the increase in voltage supplied, multiple heating elements with multiple terminal connections were required. 
The incremental cost required to support each heater, manifold, and engine variation is significant.  Not only are there design costs and manufacturing costs such as tooling, prototype and inspection, each part number must be tracked within the drawing systems and bills of material.  The service parts organization is also effected requiring increased space to shelve the permutation of parts.  Increasingly complex inventory systems and the resulting multitude of repair manuals are likely to increase customer confusion. 
Another concern arises regarding the ease of assembly of existing heaters.  As the level of difficulty of assembly increases, the associated cost of production increases.  In view of the above concerns, a need exists for a heater that may be utilized in a variety of applications without requiring a different intake manifold for each heater configuration.