Prototype racing car engines were built by Coventry and Porsche in the 1960s and 1970s.

Flat-sixteen engines are not known to have reached production.

Flat-twelve engines have been used in various racing cars, notably the Porsche 917K, during the 1960s and 1970s, and in Ferrari road cars from 1973-1996.

A prototype road car engine was built by Chevrolet in the 1960s.

Flat-ten engines are not known to have reached production.

Flat-eight engines have been used in several racing cars, mostly by Porsche in the 1960s.

Flat-six engines are mostly used in cars (particularly by the Porsche 911 sports car), and have occasionally been used in motorcycles and aircraft.

Their most common use is in smaller single-engine general aviation aircraft in which they are still manufactured and used to this day.

Flat-four engines are mostly used in cars (particularly in the earlier Volkswagen Type 1 to 4 and by Subaru in most of their models), and have occasionally been used in motorcycles.Occasionally been used in light cars, aircraft and industrial applications, mostly up until the 1960s. Flat-twin engines are mostly used in motorcycles.The most common usages of flat engines are:

Compared with V engines- the most common layout for engines with six cylinders or more- flat engines have a lower centre of mass (and a better primary balance than V6 engines), however they usually have a larger width. The advantages of flat engines are a short length, low centre of mass and suitability for air cooling.Ĭompared with the more common straight engines, flat engines have better primary balance (resulting in less vibration) however the disadvantages are increased width and the need to have two cylinder heads. They have even replaced radial engines in many smaller installations.ĭifference between two flat 6 cylinder engines: 180° V on the left, boxer on the right They are much more common in aircraft, where straight engines are a rarity and V engines have almost vanished except in historical aircraft. They are now less common in cars than straight engines (for most sub-6 cylinder applications, although straight/inline 6 cylinder engines are widely used by German brands) and V engines (for engines with six or more cylinders). Flat engines have been used in aviation, motorcycle and automobile applications. The first flat engine was built in 1897 by Karl Benz. Each pair of cylinders shares a single crankpin, so that as one piston moves inward, the other moves outward. The other configuration is effectively a V engine with a 180-degree angle between the cylinder banks. Boxer engines are a type of flat engine however, flat engines are not necessarily boxer engines. The most common configuration of flat engines is the boxer engine, in which the pistons of each opposed pair of cylinders move inwards and outwards at the same time. A flat engine should not be confused with the opposed-piston engine, in which each cylinder has two pistons sharing a central combustion chamber. These advantages are evidence of the vision that Subaru has in using the Horizontally-Opposed Engine.A flat engine, also known as a horizontally opposed engine, is a piston engine where the cylinders are located on either side of a central crankshaft.

A prodigious 350-Nm of peak torque is delivered at a lower 1,600 rpm – providing smooth, free-breathing performance at any speed. And whilst meeting the ultra-clean EURO5 emission standards, the engine delivers even more torque compared to previous models. The result is a more compact combustion chamber and greater fuel efficiency, and combined with a higher pressure common rail fuel injection, an improved oxidizing catalyst with closed Diesel Particulate Filter (DPF), a variable nozzle turbo and electric power steering, these all help to reduce fuel consumption and CO2 emissions.Ĭeramic glow plugs also quicken starting in cold weather. The SUBARU BOXER, however, was originally designed with rigidity in mind, allowing the 92.0 mm x 75.0 mm bore and stroke of the 2.0-litre petrol four-cylinder engine to be changed to a square 86.0 mm x 86.0 mm design. When petrol engines are converted to diesel, strengthening of the engine block usually makes the engine bigger and heavier. The world’s first commercial Horizontally-Opposed Diesel Engine developed for passenger vehicles is the SUBARU BOXER DIESEL.