History
The Lycoming IO-390 engine is a horizontally opposed, four-cylinder aircraft engine, manufactured by Lycoming Engines.[1][2]
There is no carburetted version of the engine, which would have been designated O-390 and therefore the base model is the IO-390.[1][2]
Design and development
The engine was originally conceived in the 1970s as the IO-400-X, but the project was never pursued.[3]
The IO-390 family of engines, which Lycoming refers to as the IO-390-X, produce 200 hp (149 kW) to 215 hp (160 kW). The IO-390 was developed from the similar IO-360 engine, by using cylinders from the IO-580[citation needed] to increase the O-360’s cylinder bore. (Although the IO-390 cylinder assembly[4] is not the same part number as the IO-580,[5] the cylinder barrels of both have a 5.318 bore and 4.375 stroke dimension.)
It features a tuned induction system, roller tappets and Slick Start ignition. The engine has a fuel injection system which meters fuel in proportion to the induction airflow with fuel vaporization taking place at the intake ports. The engine has a displacement of 390 cubic inches (6.39 litres). The cylinders have air-cooled heads
