Main Page | See live article | Alphabetical index 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. This article is from Wikipedia. All text is available under the terms of the GNU Free Documentation License.