Flat-eight engine

The advantages of a flat-eight engine are its minimal length and low centre of mass. A disadvantage is its greater width compared to a V8 or inline-eight engine. A flat-eight engine is able to have perfect primary balance and secondary balance.

A boxer-eight engine has a single piston per crankpin, which increases the offset between the cylinder banks. A boxer-eight with nine main bearings may be thought of as two boxer-four engines laid end-to-end with a 90° phase angle between their crankshafts.[1]^{(pp156,166,171–173)}

Alternatively, a flat-eight engine where corresponding pistons from the two opposing banks share a crankshaft journal is often called a "180 degree V engine". One possible configuration for this design is to use a two-plane crankshaft. Another configuration is to use a 180° single-plane crankshaft with the leading and trailing crankpins in the same position, while the two central crankpins are in the opposite position.

Buffum Model G Greyhound

One of the earliest flat-eight engines was used in the 1904 Buffum Model G Greyhound racing car, which used an engine based on two of Buffum's existing flat-four engines joined together.[2] The Model G was built in the United States and was introduced one year after the Winton Motor Carriage Company Bullet No. 2, which used a straight-8 engine. Around the same time, the first V8 engines were beginning to appear in Europe.

Several racing cars have used bespoke flat-eight engines based on two inline-four engines and a custom crankshaft. These include the 1928 Anderson Specials Number 2 built in Scotland using two Humber 9/20 engines.[3] The car is on display at the Kelvingrove Art Gallery and Museum in Glasgow.[4] Another example is a 1977 Eagle 72 chassis raced by Bruce Crower in the United States. This engine used the cylinder heads from two Chevrolet Cosworth Vega engines.[5][6][7] In 1969, a one-off engine was built for racing driver Emerson Fittipaldi to compete in the Thousand Miles of Guanabara endurance race.[8] This flat-eight engine was made by joining two 1.3 L Volkswagen flat-four crankcases with an elastomeric gasket and connecting the two crankshafts together. Several similar Volkswagen-based engines were built for Fittipaldi's racing cars in the early 1970s.[9][10][11][12]

Porsche

Main article: Porsche flat-eight engines

Porsche 771 engine

Porsche used flat-eight engines in various racing cars throughout the 1960s.

The first Porsche flat-eight was the Type 753. Work began on it in 1960, following the announcement of a 1.5 L (92 cu in) displacement limit for the 1961 Formula One season. Designed by Hans Mezger and Hans Honich, the engine includes features shaft-driven double-overhead camshafts, a two-piece magnesium crankcase casting, eight individual finned cylinder barrels, a solid crankshaft running in nine main bearings and Lucas electronic ignition.[13]^(p98)[14]^(p324) The version of the Type 753 used for its debut at the 1962 Dutch Formula One Grand Prix produced 138 kW (185 hp).[15] At the 1962 French Grand Prix, the Type 753 engine delivered Porsche's only F1 race win as a constructor, in an 804 driven by Dan Gurney. The 753 also influenced the design of the flat-six engine used in the first-generation Porsche 911.[16]^(p26)

A 2.0 L (122 cu in) version of the Porsche flat-eight, designated the Type 771, was developed alongside the Type 753.[14]^(p324) This engine was intended for sports car and endurance racing, and was used in the Porsche 718 W-RS, Porsche 904/8[16]^(p33)), Porsche 906,[17] Porsche 907, Porsche 909 and Porsche 910 racing cars between 1962 and 1968. A version of the Type 771 enlarged to 2.2 l (134 cu in) was designated Type 771/1.

In 1968, a new flat-eight engine called the Type 908 was introduced in the Porsche 908, which competed in the Group 6 Prototype-Sports Cars category. The Type 908 was not based on the Type 771, but instead the Type 916 flat-six racing six-cylinder engine with two additional cylinders.[18] Porsche also installed Type 908 engines into two Porsche 914/8 mid-engined road cars. The first of these was a concept study built by the head of the racing department, and the second was built as a 60th birthday present for the company chairman.[19]

Although Porsche never produced any road cars with a flat-eight engine, a prototype of such an engine was built in the late 1960s and early 1970s. During this time, Posche had been commissioned by Volkswagen to develop "Project EA266", a replacement for the Volkswagen Beetle.[20] Project EA266 was powered by a water-cooled inline-four engine which was mounted longitudinally under the rear passenger seat with the cylinders oriented horizontally. Porsche investigated using the Project EA266 chassis as the basis for a mid-engined replacement for the Porsche 911 called the "Typ 1966".[21] As part of the Typ 1966 development process, a prototype water-cooled flat-eight engine was built.[22]^(pp59,68) However, Project EA266 was cancelled by Volkswagen, all materials relating to the Typ 1966 were destroyed, including the prototype flat-eight engine.[23]^(pp73,86)

Jabiru 5100 aircraft engine

Several flat-eight aircraft engines have been produced over the years:

• 1961-present Lycoming IO-720. Air-cooled, 11.8 L (722 cu in)
• 1969-1975 Continental Tiara 8-380 (O-540) and T8-450 (O-540). Air-cooled, 8.9 L (541 cu in)
• 1997-200? Jabiru 5100. Air-cooled, 5.1 L (310 cu in)[24]
• 2013-???? Engineered Propulsion Systems Vision 350. Turbo-diesel, water-cooled, 4.4 L (269 cu in)[25][26]

Flat-eight engines are seldom used in marine applications, with the 1957 Fageol VIP 88 outboard engine being a rare example of a production engine. The VIP 88 consisted of two 0.7 L (44 cu in) Crosley engine blocks joined on a common crankshaft.[27][28]

Another marine engine was the one-off Miller 148 marine engine which was built in 1928 and used in the racing boat Miss Rioco III. The Miller 148 had dual overhead camshafts and a displacement of 2.4 L (148 cu in).[29][30]

• Straight-eight engine
• V8 engine
• W8 engine