The Subaru EJ204 was a 2.0-litre horizontally-opposed (or 'boxer') four-cylinder petrol engine with double overhead camshafts. The naturally aspirated E204 engine was initially introduced in the 2005 Subaru GD/GG Impreza and 2006 Subaru BL/BP Liberty as a more powerful alternative to the single overhead cam EJ202 engine, but effectively replaced the EJ202 when the GE/GH Impreza was released in