From Wikipedia, the free encyclopedia.
A Flat-4 is a four cylinder internal combustion engine where the cylinders are arranged in a flat configuration.
This geometry is common on small airplanes.
In automobile the VW Beetle and early Porsche models were also powered by a flat-4.
Subaru also produce water-cooled flat-4 engine that are strangely marketed as H-4, despite the fact that their configuration has nothing to do with a real H engine
Air-cooled flat-4 engines are also common in aviation.
