The first known working V8 engine was produced by the French company Antoinette in 1904, while the American 1914–1935 Cadillac L-Head engine is considered the first automotive V8 engine to be produced in significant quantities. The popularity of V8 engines in cars was greatly increased following the 1932 introduction of the Ford Flathead V8.

Volkswagen Group introduced the first VR6 engine in 1991 and VR6 engines currently remain in production. From 1997 to 2006, Volkswagen also produced a five-cylinder VR5 engine based on the VR6

The name VR6 comes from the German initials for a V engine (German: V-Motor) and a straight (inline) engine (German: Reihenmotor), therefore the VR engine is described as a "Vee-Inline engine" (VR-Motor).

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. Boxer engines are a type of flat engine; however, flat engines are not necessarily boxer engines. The other configuration is effectively a V engine with a 180-degree angle between the cylinder banks. Each pair of cylinders shares a single crankpin, so that as one piston moves inward, the other moves outward.
first flat engine was built in 1897 by Karl Benz. Flat engines have been used in aviation, motorcycle and automobile applications. 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). They are much more common in aircraft, where straight engines are a rarity and V engines have almost vanished except in historical aircraft. They have even replaced radial engines in many smaller installations.

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.

A straight engine is considerably easier to build than an otherwise equivalent horizontally opposed or V engine, because both the cylinder bank and crankshaft can be milled from a single metal casting, and it requires fewer cylinder heads and camshafts. In-line engines are also smaller in overall physical dimensions than designs such as the radial, and can be mounted in any direction. Straight configurations are simpler than their V-shaped counterparts. Although six-cylinder engines are inherently balanced, the four-cylinder models are inherently off balance and rough, unlike 90-degree V fours and horizontally opposed 'boxer' four cylinders.

W16 engines are rarely produced, with the notable exception of the Volkswagen Group 8.0 WR16 engine, which has been used since 2005 in the Bugatti Veyron, Bugatti Chiron and their related models.

In practice, the W8 engine is created from two narrow-angle (15 degree) VR4 engines mounted at an angle of 72 degrees from each other on a common crankshaft. Thus, the resulting four banks align to form a "W".


The sole W8 engine to reach production was the Volkswagen 4-litre W8 engine, which was available in the Volkswagen Passat (B5.5) from September 2001 to September 2004.^[2] Production was minimal at only 11,000 units.

This engine had a displacement of 3,999 cc (4 L), had a peak power rating of 202 kW (271 hp) at 6,000 rpm and a peak torque rating of 370 N⋅m (273 lb⋅ft) at 2,750 rpm. Power and torque outputs were lower than competitors V8 engines with similar capacity, however the W8 engine was praised for its smoothness.

Sales of the W8-engined Passat models were poor, and production was discontinued when the next generation of Passat switched from a longitudinal engine to a transverse engine layout, which made packaging of the wide W8 engine difficult. The W8 was effectively replaced by the Volkswagen 3.6-litre VR6 petrol engine.

W8 engines are much less common than V8 engines, and the only W8 engine to reach production was manufactured by Volkswagen from 2001–2004.

The radial configuration was commonly used for aircraft engines before gas turbine engines became predominant.

Compared to the reciprocating piston engine, the Wankel engine has more uniform torque; less vibration; and, for a given power, is more compact and weighs less.

The rotor, which creates the turning motion, is similar in shape to a Reuleaux triangle, except the sides have less curvature. Wankel engines deliver three power pulses per revolution of the rotor using the Otto cycle. However, the output shaft uses toothed gearing to turn three times faster giving one power pulse per revolution. This can be seen in the animation below. In one revolution, the rotor experiences power pulses and exhausts gas simultaneously, while the four stages of the Otto cycle occur at separate times. For comparison, in a two-stroke piston engine there is one power pulse for each crankshaft revolution (as with a Wankel engine output shaft) and, in a four-stroke piston engine, one power pulse for every two revolutions.

The four-stage Otto cycle of intake, compression, ignition, and exhaust occurs each revolution of the rotor at each of the three rotor faces moving inside the oval-like epitrochoidal housing, enabling the three power pulses per rotor revolution.