Flat-eight engine

{{see also|Flat 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 linear 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.{{cite book |last=Smith |first=Phillip H. |date=1977 |title=The Design and Tuning and Competition Engines |url=https://archive.org/details/designtuningofco0000smit|url-access=registration |publisher=Robert Bentley Inc. |isbn=0-8376-0140-1 }}{{refpage|pages=156,166,171–173}}

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 uses a two-plane crankshaft. Another configuration uses 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.

Image:Buffum Model G Greyhound racer 1904.jpg 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.{{cite web |url=http://vintagemotoring.blogspot.com/2013/07/1904-central-greyhound-8-cylinder-racer.html |title=1904 Central Greyhound 8-cylinder racer by H. H. Buffum Co. |date=12 July 2013 |last=Evans |first=Steve |website=vintagemotoring.blogspot.com |access-date=9 May 2019 |archive-date=24 May 2021 |archive-url=https://web.archive.org/web/20210524115807/http://vintagemotoring.blogspot.com/2013/07/1904-central-greyhound-8-cylinder-racer.html |url-status=dead }} 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.{{cite magazine |last=B. |first=W. |date=October 1962 |title=The Anderson Specials |magazine=MotorSport magazine |page=26 }} The car is on display at the Kelvingrove Art Gallery and Museum in Glasgow.{{cite web |url=https://www.dailyrecord.co.uk/lifestyle/motoring/anderson-special-race-car-built-11867516 |title=The Anderson Special - a race car built in Scotland far ahead of its time |last=Barry |first=Maggie |date=17 January 2018 |website=www.dailyrecord.co.uk }} 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.{{cite news |author= |title=Ingenious Powerplant Wins Engineer Award |url=https://www.newspapers.com/newspage/106912839/ |work=The Indianapolis Star |date=21 May 1977 |page=24 }}{{cite web |url=https://www.crower.com/crower-history/ |title=Crower History |website=www.crower.com }}{{cite web |url=https://www.oldracingcars.com/eagle/72/ |title=Eagle 1972 Indy car-by-car histories |date=25 March 2019 |last=Brown |first=Allen |website=www.oldracingcars.com }} In 1969, a one-off engine was built for racing driver Emerson Fittipaldi to compete in the Thousand Miles of Guanabara endurance race.{{cite web |url=https://jalopnik.com/emerson-fittipaldis-double-engined-volkswagen-beetle-5799726 |title=Emerson Fittipaldi's double-engined Volkswagen Beetle |last=Nishihata |first=Leo |date=8 May 2011 |website=jalopnik.com }} 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.{{cite web|url=http://www.lorenagt.com/p-05-carro-P-01.htm |title=Prototype "Jamaro" |website=www.lorenagt.com |language=pt }}{{cite web |url=http://www.pumaclassic.com.br/2010/11/reportagens-oficina-1972-motor-8.html |title=Reportagens - Oficina 1972 - Motor 8 cilindros |date=12 November 2010 |last=Nicoliello |first=Felipe |website=www.pumaclassic.com.br |language=pt |trans-title=News - Workshop 1972 - 8 cylinder engine }}{{cite web |url=http://www.pumaclassic.com.br/2014/11/historia-puma-motor-boxer-8-cilindros.html |title=História Puma - Motor boxer 8 cilindros |date=1 November 2014 |last=Nicoliello |first=Felipe |website=www.pumaclassic.com.br |language=pt |trans-title=Puma History - 8-cylinder boxer engine }}{{cite web |url=http://chicobiela.nafoto.net/photo20091018152155.html |title=Preparação de motores VW AR e fuscas |date=18 October 2009 |last=Biela |first=Chico |website=chicobiela.nafoto.net |language=pt |trans-title=Preparation of VW AR engines and fuscas }}

{{main|Porsche flat-eight engines}}

File:Porsche 771 engine front-left Porsche Museum.jpg

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 {{convert|1.5|L|cuin|0|abbr=on}} 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.{{cite book |last=Long |first=Brian |date=15 October 2008 |title=Porsche Racing Cars: 1953 to 1975 |url=https://books.google.com/books?id=NMNnEN9L-cgC |publisher=Veloce Publishing |isbn=978-1904788447 }}{{refpage|page=98}}{{cite book |last=Whitelock |first=Mark |date=10 August 2006 |title=1 1/2-litre Grand Prix Racing: Low Power, High Tech |url=https://books.google.com/books?id=pf-bn_ihlhYC |publisher=Veloce Publishing |isbn=978-1845840167 }}{{refpage|page=324}} The version of the Type 753 used for its debut at the 1962 Dutch Formula One Grand Prix produced {{convert|185|hp|kW|0|abbr=on|order=flip}}.{{cite magazine |last=Söhnke |first=Michael |date=April–May 2005 |title=A Relic of the Sixties |url=https://files1.porsche.com/filestore/download/uk/none/christophorus-aprilmay2005-history-PDF/default/4e450861-737f-4f0c-aca7-eb4db83e796d/History-A-Relic-of-the-Sixties.pdf |magazine=Christophorus |publisher=Porsche AG |volume=313 |pages=38–44 |access-date=2019-05-09 |archive-date=2019-05-08 |archive-url=https://web.archive.org/web/20190508174537/https://files1.porsche.com/filestore/download/uk/none/christophorus-aprilmay2005-history-PDF/default/4e450861-737f-4f0c-aca7-eb4db83e796d/History-A-Relic-of-the-Sixties.pdf |url-status=dead }} 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.{{cite book |last=Long |first=Brian |date=21 November 2003 |title=Porsche 911, 1963 to 1971 |publisher=Veloce |isbn=978-1903706282 }}{{refpage|page=26}}

A {{convert|2.0|L|cuin|0|abbr=on}} version of the Porsche flat-eight, designated the Type 771, was developed alongside the Type 753.{{refpage|page=324}} This engine was intended for sports car and endurance racing, and was used in the Porsche 718 W-RS, Porsche 904/8{{refpage|page=33}}), Porsche 906,{{cite web |title=Alan Hamilton, Australian Champion: His Porsche 904/8 and two 906's… |url=https://primotipo.com/2015/08/20/alan-hamilton-his-porsche-9048-and-two-906s/ |website=www.primotipo.com |access-date=29 September 2019 |language=en |date=20 August 2015}} Porsche 907, Porsche 909 and Porsche 910 racing cars between 1962 and 1968. A version of the Type 771 enlarged to {{convert|2.2|L|cuin|0|abbr=on}} 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.{{cite web |url=https://www.porscheroadandrace.com/porsche-twin-cam-6-cylinder-engine/ |title=Porsche twin-cam 6-cylinder engine |last=Smale |first=Glen |date=19 January 2018 |website=www.porscheroadandrace.com }} 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.{{cite magazine |author= |title=VW-Porsche 914 turns 40. |url=https://www.clubvw.org.au/assets/pdf/Zeitschrift/2009/2009-06_June.pdf |magazine=Zeitschrift |publisher=Club Veedub Sydney Inc. |date=June 2009 |pages=15–16 }}

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, Porsche had been commissioned by Volkswagen to develop "Project EA266", a replacement for the Volkswagen Beetle.{{cite web |last=Torchinsky |first=Jason |date=29 December 2014 |url=https://jalopnik.com/this-fascinating-stillborn-vw-prototype-would-have-been-1675948679 |title=This Fascinating Stillborn VW Prototype Would Have Been Revolutionary |website=jalopnik.com}} 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".{{cite web |title=Porsche 911 history: the complete timeline from 901 to 992 - Porsche 911: 1964 - 1989 |url=https://www.evo.co.uk/porsche/911/22001/porsche-911-history-the-complete-timeline-from-901-to-992/page/0/1 |website=www.evo.co.uk |access-date=29 September 2019 |language=en}} As part of the Typ 1966 development process, a prototype water-cooled flat-eight engine was built.{{cite book |last=Leffingwell |first=Randy |date=30 July 2019 |title=The Complete Book of Porsche 911: Every Model Since 1964 |publisher=Motorbooks |isbn=978-0760365038 }}{{refpage|pages=59,68}} However, Project EA266 was cancelled by Volkswagen, all materials relating to the Typ 1966 were destroyed, including the prototype flat-eight engine.{{cite book |last=Leffingwell |first=Randy |date=10 November 2005 |title=Porsche 911: Perfection by Design |publisher=Motorbooks |isbn=978-0760320921 }}{{refpage|pages=73,86}}

A 2.0-litre flat-eight engine is used in Great Wall Motor's Souo S2000 touring motorcycle.{{cite news |last=Chilton |first=Chris |date=2024-11-04 |title=China’s GWM Souo S2000 Flat-8 Motorcycle Wants To Run The Honda Goldwing Off The Road |url=https://www.carscoops.com/2024/11/chinas-gwm-souo-s2000-flat-8-motorcycle-wants-to-run-the-honda-goldwing-off-the-road/ |website=Carscoops |publisher=Carscoops |location=US |access-date=2024-11-12}}

Image:Jabiru5100-180hp.jpg aircraft engine]]

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

• 1948-1961 Lycoming GSO-580 Air-cooled, 9.47 L (578 cu in)
• 1961–present Lycoming IO-720. Air-cooled, {{convert|722|cuin|L|1|abbr=on|order=flip}}
• 1969-1975 Continental Tiara 8-380 (O-540) and T8-450 (O-540). Air-cooled, {{convert|541|cuin|L|1|abbr=on|order=flip}}
• 1997-200? Jabiru 5100. Air-cooled, {{convert|310|cuin|L|1|abbr=on|order=flip}}{{cite web |url=http://www.jabiru.net.au/8%20cylinderbodyFrame-1.htm |title=Jabiru 8 Cylinder Engine |date=4 March 2009 |access-date=17 April 2019 |archive-url=https://web.archive.org/web/20091002094521/http://www.jabiru.net.au/8%20cylinderbodyFrame-1.htm |archive-date=2 October 2009 }}
• 2013-???? Engineered Propulsion Systems Vision 350. Turbo-diesel, water-cooled, {{convert|4.4|L|cuin|0|abbr=on}}{{cite web |url=https://eps.aero/eps-launches-diesel-aero-engine-following-successful-propeller-vibration-testing-at-hartzell-propeller/ |title=EPS Launches Diesel Aero-Engine Following Successful Propeller Vibration Testing at Hartzell Propeller |date=24 January 2013 |website=eps.aero |access-date=9 May 2019 |archive-date=24 May 2021 |archive-url=https://web.archive.org/web/20210524121310/https://eps.aero/eps-launches-diesel-aero-engine-following-successful-propeller-vibration-testing-at-hartzell-propeller/ |url-status=dead }}{{cite web |url=https://patents.google.com/patent/EP2766588B1/en |title=An aerodiesel engine |website=patents.google.com }}

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 {{convert|44|cuin|L|1|abbr=on|order=flip}} Crosley engine blocks joined on a common crankshaft.{{cite web |url=http://www.fiberglassics.com/library/index.php?title=Fageol |title=Fageol |website=www.fiberglassics.com }}{{cite web |url=http://crosleyautoclub.com/EngineTree/Crosley_Eng_Tree-3.html |title=Crosley Engine Family Tree - The Later Years |website=crosleyautoclub.com }}

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 {{convert|148|cuin|L|1|abbr=on|order=flip}}.{{cite web |url=https://www.milleroffy.com/Miller%20148%20Flat-Eight%20Marine.html |title=The Miller 148 Flat-Eight Marine |website=www.milleroffy.com }}{{cite web |url=https://www.prewarcar.com/vintage-pornography-the-naked-miller |title=Vintage Pornography: the naked Millers |date=26 March 2013 |website=www.prewarcar.com }}

• Straight-eight engine
• V8 engine
• W8 engine

{{Reflist|30em}}

{{Piston engine configurations}}

Flat-08

08