A V12 engine is a twelve-cylinder piston engine where two banks of six cylinders are arranged in a V configuration around a common crankshaft. V12 engines are more common than V10 engines. However, they are less common than V8 engines. The first V12 engine was built in 1904 for use in racing boats. Due to the balanced nature of the engine and the smooth delivery of power, V12 engines were found in early luxury automobiles, boats, aircraft, and tanks. Aircraft V12 engines reached their apogee during World War II, following which they were mostly replaced by jet engines. In Formula One racing, V12 engines were common during the late 1960s and early 1990s. Applications of V12 engines in the 21st century have been as marine engines, in railway locomotives, as large stationary power as well as in some European sports and luxury cars. Design Balance and smoothness Each bank of a V12 engine essentially functions as a straight-six engine, which by itself has perfect primary and secondary engine balance. A four-stroke V12 engine has even firing order at V-angles of 60, 120, or 180 degrees Many V12 engines use a V-angle of 60 degrees between the two banks of cylinders. V12 engines with other V-angles have been produced, sometimes using split crankpins to reduce the unbalanced vibrations. The drawbacks of V12 engines include extra cost, complexity, friction losses, and external size and weight, compared with engines containing fewer cylinders. At any given time, three of the cylinders in a V12 engine are in their power stroke, which increases the smoothness of the power delivery by eliminating gaps between power pulses. A V12 engine with a 180 degree V-angle is often called a flat-twelve engine. These are also sometimes called 'boxer twelve' engines, however this terminology is incorrect for the majority of 180-degree V12 engines, since they use shared crankpins and are therefore not configured as boxer engines. Theoretically, the rotating parts of a V12 racing engine could be lighter than a crossplane V8 engine of similar displacement due to the V12 engine not requiring counterweights on the crankshaft or as much inertial mass for the flywheel. In addition, the exhaust system of a V12 engine is much simpler than would be required for a crossplane V8 engine to achieve pulsed exhaust gas tuning. However, the use of V12 engines in motor racing is uncommon in the 21st century. Size and