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{{short description|Type of car engine}}
[[File:Nissan VQ35DE 005.jpg|250px|thumb|A [[cylinder head]] of a four [[
== Multi-valve rationale ==
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=== Multi-valve engine design ===
A multi-valve engine design has three, four, or five [[poppet valve|valves]] per cylinder to achieve improved performance.
{{anchor |Three-valve}}
* '''Three-valve cylinder head'''
This has a single large exhaust valve and two smaller intake valves. A three-valve layout allows better breathing than a two-valve head, but the large exhaust valve results in an RPM limit no higher than a two-valve head. The manufacturing cost for this design can be lower than for a four-valve design. The three-valve design was common in the late 1980s and early 1990s; and from 2004 the main valve arrangement used in [[Ford
{{anchor |Four-valve}}
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{{anchor |Five-valve}}
* '''Five-valve cylinder head'''
Less common is the five-valve head, with two exhaust valves and three inlet valves. All five valves are similar in size. This design allows excellent breathing, and, as every valve is small, high RPM and very high power outputs are theoretically available. Although, compared to a four-valve engine, a five-valve design should have a higher maximum RPM, and the three inlet ports should give efficient cylinder-filling and high gas turbulence (both desirable traits), it has been questioned whether a five-valve configuration gives a cost-effective benefit over four-valve designs. The rise of direct injection may also make five-valve heads more difficult to engineer, as the injector must take up some space on the head. After making five-valve [[Yamaha Genesis engine|Genesis engines]] for several years, [[Yamaha Motor Company|Yamaha]] has since reverted to the cheaper four-valve design
Examples of the five-valve engines are the various [[List of Volkswagen Group petrol engines#1.8 R4 20vT (EA113/EA827)|1. {{anchor |Beyond}}
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[[File:SUBARU EJ25 i-AVLS.jpg|thumb|Cutaway model of Subaru's [[Active Valve Control System|i-AVLS]] variable valve timing system on SOHC 4-valve-per-cylinder [[Subaru EJ engine|EJ25 boxer engine]] at Tokyo Motor Show 2007.]]
[[Turbocharging]] and [[Supercharger|supercharging]] are technologies that also improve engine breathing, and can be used instead of, or in conjunction with, multi-valve engines. The same applies to [[variable valve timing]] and [[
== Cars and trucks ==
=== Before 1914 ===
The 1908 Ariès VT race cars had 1.4 litre supercharged single cylinder engines with four valve per cylinder desmodromic systems. (Source: [https://www.desmodromology.nl/aries-2/ <nowiki>[1]</nowiki>])
The 1910 Isotta-Fraschini Tipo KM had a 10.6 litre inline 4 with single overhead camshaft and four valves per cylinder and it had one of the first engines with fully enclosed overhead valve gear (source: [[Isotta Fraschini Tipo KM]] [https://www.bonhams.com/auctions/16133/lot/316/] and [https://images2.bonhams.com/image?src=Images/live/2008-04/07/7637601-1-23.jpg&width=960])
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[[A.L.F.A. 40/60 GP]] was a fully working early racing car prototype made by the company now called [[Alfa Romeo]]. Only one example was built in 1914, which was later modified in 1921. This design of [[Giuseppe Merosi]] was the first Alfa Romeo [[DOHC]] engine. It had four valves per cylinder, 90-degree valve angle and twin-spark ignition.<ref name="velocetoday.com">{{cite web|url=http://www.velocetoday.com/cars/cars_75.php|title=Alfa Designers|access-date=2011-12-30|work=velocetoday.com}}</ref> The GP engine had a displacement of 4.5-liter (4490 cc) and produced {{convert|88|bhp|kW|0|abbr=on}} at 2950 rpm (14.7 kW/liter), and after modifications in 1921 {{convert|102|bhp|kW|0|abbr=on}} at 3000 rpm. The top speed of this car was 88-93 mph (140–149 km/h). It wasn't until the 1920s when these [[DOHC]] engines came to Alfa road cars like the [[Alfa Romeo 6C]].
In 1916 US automotive magazine ''Automobile Topics'' described a four-cylinder, four-valve-per-cylinder car engine made by Linthwaite-Hussey Motor Co. of Los Angeles, CA, USA: ''"Firm offers two models of high-speed motor with twin intakes and exhausts."''.<ref>{{cite book |url=https://books.google.com/books?id=_OMDAAAAMBAJ |title=Engines: A Century of Progress (Popular Mechanics, Jan 1985, pp. 95-97, 120, 122) |author=Mort Schultz |access-date=2011-12-26 |date=January 1985 }}</ref>
Early multi-valve engines in [[T-head engine|T-head]] configuration were the 1917 ''Stutz'' straight-4, White Motor Car Model GL
Multi-valve engines continued to be popular in racing and sports engines. Robert M. Roof, the chief engineer for Laurel Motors, designed his multi-valve ''Roof Racing Overheads'' early in the 20th century. Type A 16-valve heads were successful in the teens, Type B was offered in 1918 and Type C 16-valve in 1923. [[Frank Lockhart (racing driver)|Frank Lockhart]] drove a Type C overhead cam car to victory in Indiana in 1926.<ref>{{cite web |url=http://www.nwvs.org/Technical/Engines/EngineRoofGrpAlpha.shtml |title=Roof Alphabetical Index and Images (nwvs.org) |author=Northwest Vintage Speedsters |access-date=2011-12-23 }}</ref><ref>{{cite web |url=http://www.mtfca.com/HOF/Fame.htm |title=Robert M. Roof (MTFCA.com) |author=Model T Ford Club of America |access-date=2011-12-23 }}</ref>
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Debuting at the 1968 Japanese Grand Prix in the original {{Convert|300|PS|kW hp|0|abbr=on}} 3.0-liter version the [[Toyota 7]] engine participated in endurance races as a 5.0-liter (4,968 cc) non-turbo V8 with DOHC and 32-valves. It produced {{Convert|600|PS|kW hp|0|abbr=on}} at 8,000 rpm (88.8 kW/liter) and {{Convert|55.0|kgm|Nm lbft|0|abbr=on}} at 6,400 rpm.
There is much discussion about which was the first 'mass-produced' car to use
For a four The 1975 [[Chevrolet Cosworth Vega]] featured a DOHC multi-valve head designed by [[Cosworth|Cosworth Engineering]] in the UK. This 122-cubic-inch straight-4 produced {{Convert|110|bhp|kW PS|0|abbr=on}} at 5600 rpm (0.90 bhp/cid; 41.0 kW/liter) and {{Convert|107|lbft|Nm|abbr=on}} at 4800 rpm.<ref>{{cite web |url= http://upload.wikimedia.org/wikipedia/en/f/f4/1975_Cosworth_Vega_Ad.jpg |title=1975 Cosworth Vega advertisement (Motor Trend Magazine, 1975)
The 1976 [[Fiat 131#Series 1|Fiat 131 Abarth]] (51.6 kW/liter), 1976 [[Lotus Esprit]] with [[Lotus 907]] engine (54.6 kW/liter, 1.20 bhp/cid), and 1978 [[BMW M1]] with [[BMW M88]] engine (58.7 kW/liter, 1.29 bhp/cid) all used four valves per cylinder. The BMW M88/3 engine was used in the 1983 [[BMW M6]]35CSi and in the 1985 [[BMW M5]].
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The 1978 [[Porsche 935/78]] racer used a twin turbo 3.2-liter [[flat-6]] (845 bhp/630 kW@8,200 rpm; 784 Nm/578 ft.lbs@6,600 rpm). The water-cooled engine featured four valves per cylinder and output a massive 196.2 kW/liter. Porsche had to abandon its traditional aircooling because the multi-valve DOHC hampered aircooling of the spark plugs. Only two cars were built.
[[Ferrari]] developed their ''[[Ferrari Dino engine#Quattrovalvole|Quattrovalvole]]'' (or QV) engines in the 80s. Four valves per cylinder were added for the 1982 [[Ferrari 308 GTB|308]] and [[Ferrari Mondial|Mondial]] ''Quattrovalvole'', bringing power back up to the pre-[[fuel injection|FI]] high of {{Convert|245|hp|kW|0|abbr=on}} . A very unusual Dino Quattrovalvole was used in the 1986 [[Lancia Thema|Lancia Thema 8.32]]. It was based on the 308 QV's engine, but used a split-plane crankshaft rather than the Ferrari-type flat-plane. The engine was constructed by [[Ducati]] rather than Ferrari, and was produced from 1986 through 1991. The Quattrovalvole was also used by Lancia for their attempt at the [[World Sportscar Championship]] with the [[Lancia LC2|LC2]]. The engine was twin-turbocharged and destroked to 2.65 litres, but produced {{Convert|720|hp|kW|0|abbr=on}} in qualifying trim. The engine was later increased to 3.0 litres and increased power output to {{Convert|828|hp|kW|0|abbr=on}}. The 1984 [[Ferrari Testarossa]] had a 4.9-liter [[flat-12]] with four valves per cylinder. Almost 7,200 Testarossa were produced between 1984 and 1991.
In 1985 [[Lamborghini]] released a [[Lamborghini Countach#5000QV|Countach ''Quattrovalvole'']], producing {{Convert|455|PS|kW hp|0|abbr=on}} from a 5.2-liter (5167 cc) [[Lamborghini V12]] engine (64.8 kW/liter).
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The 2.0-liter Nissan [[Nissan FJ engine|FJ20]] was one of the earliest [[straight-4]] mass-produced Japanese engines to have both a DOHC 16-valve configuration (four valves per cylinder, two intake, two exhaust) and [[electronic fuel injection]] (EFI) when released in October 1981 in the sixth generation [[Nissan Skyline]]. Peak output was {{Convert|148|hp|kW|0|abbr=on}} at 6,000 rpm and {{Convert|133|lbft|Nm|abbr=on}} at 4,800 rpm. The FJ20 was also offered with a turbocharger, producing {{Convert|188|hp|kW|0|abbr=on}} at 6,400 rpm and {{Convert|166|lbft|Nm|abbr=on}} at 4,800 rpm.
Following Nissan's lead, Toyota released the 1.6-liter (1,587 cc)
In 1986 [[Volkswagen]] introduced a multi-valved [[Volkswagen Golf Mk2#Golf GTI & GTI 16v|Golf GTI 16V]]. The 16-valve 1.8-liter straight-4 produced 139 PS (102 kW; 137 bhp) or 56.7 kW/liter, almost 25% up from the 45.6 kW/liter for the previous 8-valve Golf GTI engine.
The [[GM Quad-4 engine|GM Quad 4]] multi-valve engine family debuted early 1987. The Quad 4 was the first mainstream multi-valve engine to be produced by GM after the [[Chevrolet Cosworth Vega]]. The NA Quad 4 achieved {{Convert|1.08|bhp|kW PS|0|abbr=on}} per cubic inch (49.1 kW/liter).<ref name="DanMcCosh4valves"/><ref>{{cite book |url= https://books.google.com/books?id=HOQDAAAAMBAJ |title=Quad 4: The Inside Story (Popular Mechanics, February 1988, pp.62-65) |author=Mike Allen |access-date=2011-12-23 |date=February 1988 }}</ref> Such engines soon became common as Japanese manufacturers adopted the multi-valve concept.
==== Three valves ====
[[File:Head D15A3.JPG|250px|thumb|A [[cylinder head]] from a 1987 [[Honda CRX|Honda CRX Si]] showing SOHC, rocker arms, valve springs, and other components. This is a multi-valve configuration with two intake valves and one exhaust valve for each cylinder.]]
The 1975 [[Honda Civic]] introduced Honda's 1.5-liter SOHC 12-valve straight-4 engines. Nissan's 1988–1992 SOHC [[Nissan KA engine|KA24E]] engine had three valves per cylinder (two intakes, one exhaust) as well. Nissan upgraded to
In 1988, Renault released a 12 valve version of its Douvrin 4 cylinder 2.0l SOHC.
Mercedes and Ford
The 1989 [[Citroën XM]] was the first 3-valve diesel-engined car.
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[[File:NISSAN SR20VE CYL-HEAD 02.jpg|250px|thumb|[[Nissan SR engine#SR20VE|Nissan SR20VE]] 2.0-liter straight-4-cylinder head with [[DOHC]], Nissan's [[Neo VVL]] [[variable valve timing]] with lift control and four valves per cylinder.]]
[[File:Diesel engine valve train.JPG|250px|thumb|Multi-valve train of Volvo's 2005 truck diesel engine D13A, a 12.8-liter turbocharged straight-6 (21.1-28.1 kW/liter) with SOHC and four valves per cylinder located around a central injector, and VEB engine brake that operates both exhaust valves.]]
Examples of SOHC four-valve engines include
The [[V12 engine]]s of many [[World War II]] fighter aircraft also used a SOHC configuration with four valves for each cylinder.
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[[Peugeot]] had a triple overhead cam five-valve Grand Prix car in 1921.<ref name="SportsCarMarket1921Peugeot"/>
In April 1988 an [[Audi
[[Mitsubishi Motors|Mitsubishi]] were the first to market a car engine with five valves per cylinder, with the 548 cc ''[[Mitsubishi 3G8 engine|3G81]]'' engine in their [[Mitsubishi Minica|Minica Dangan ZZ]] [[kei car]] in 1989.<ref name="wards">{{Cite journal | title = A baby that sprints: tiny Mitsubishi engine blasts off with five valves | journal = Ward's Auto World | issue = April 1989 }}</ref><ref>{{cite web |url=http://autospeed.com.au/cms/article.html?&A=2705 |title=Mighty Minica ZZ-4 (Autospeed Issue 353, 19 October 2005) |author=Michael Knowling |access-date=2011-12-26 }}</ref>
[[Yamaha Motor Company|Yamaha]] designed the five-valve cylinder head for the [[Toyota A engine#4A-GE (20-valve)|
For their [[Yamaha YZ250F|YZ250F]] and [[Yamaha YZ450F|YZ450F]] motocross bikes, Yamaha developed five-valve engines.
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==== Pushrod ====
Although most multi-valve engines have [[overhead camshaft]]s, either SOHC or [[DOHC]], a multivalve engine may be a pushrod [[overhead valve engine]] (OHV) design. [[
engine using four pushrods, four rockers and four valves per cylinder. The 6.0 and 6.4 Powerstroke engine built by Navistar also used pushrods with four-valve heads. Pushrod multi-valve systems are common on diesels because they need to be able to meet emissions standards, but also produce more low-end torque. The Harley-Davidson ''Milwaukee Eight'' engine, introduced in 2016, uses four-valves per cylinder driven by pushrods and a single in-block camshaft.<ref>{{cite web|last1=Bennett|first1=Jay|title=Milwaukee Eight Multi-Valve|url=http://www.popularmechanics.com/cars/motorcycles/a22601/harley-davidson-new-engine-milwaukee-eight/|website=Popular Mechanics|publisher=HEARST DIGITAL MEDIA|access-date=16 August 2017|date=2016-08-29}}</ref><ref>{{cite web|last1=Cook|first1=Marc|title=HD Pushrods|url=http://www.motorcyclistonline.com/harleys-all-new-milwaukee-eight-big-twin#page-4|website=Motorcyclist Online|publisher=Bonnier Corporation|access-date=16 August 2017}}</ref>
==== Turbocharged ====
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Examples of motorcycles with multivalve-engines include:
* 1914 [[Peugeot]] Grand Prix racer, 500 cc DOHC 8-valve parallel twin (top speed over 122 km/h).<ref>{{cite web |url=http://thebestmotorcycles-oi.blogspot.com/2010/01/peugeot-racers-part-1.html |title=Peugeot Racers - Part 1 (The Best Motorcycle, Jan 26, 2010) |author= Yves J. Hayat & Bernard Salvat |access-date=2011-12-27 }}</ref>
* 1915 [[Indian (motorcycle)|Indian]] [[Board track racing|board track racer]], 61-cid (1.0-liter) OHV 8-valve V-twin.<ref>{{cite web |url=https://www.youtube.com/watch?v=TfEZyCccKTs |archive-url=https://ghostarchive.org/varchive/youtube/20211222/TfEZyCccKTs |archive-date=2021-12-22 |url-status=live|title=1915 Indian 8 Valve Boardtrack Racer (YouTube.com video, Mar 18, 2010) |author=Yesterdays.nl |website=[[YouTube]] |access-date=2011-12-27 }}{{cbignore}}</ref>
* 1921 [[Triumph Ricardo]] 499 cc OHV 4-valve single-cylinder machine, copied by [[Rudge-Whitworth]] with their 1924 [[Rudge-Whitworth#Rudge Four|Rudge Four]] 350 cc OHV 4-valve single-cylinder machine, and 1929 [[Rudge Ulster]] 500 cc OHV 4-valve single-cylinder machine.
* 1923 [[Anzani|British Anzani]] 1098cc OHV 8-Valve V-twin, used in [[Morgan cars|Morgan three-wheelers]] and [[McEvoy Motorcycles|McEvoy]] motorcycles
* 1972 [[Honda XL250]] "pent-roof" SOHC 4-valve single-cylinder machine (the first mass-produced 4-valve motorcycle).
* 1973 [[Yamaha TX500]] "pent-roof" 500cc DOHC 8-valve parallel-twin (the first mass-produced DOHC 4-valve per cylinder motorcycle)<ref>{{cite web |url=http://www.tobyfolwick.com/tx750/textual/cm1289.php |title=YAMAHA TX500/750: A QUESTION OF BALANCE |publisher=Tobyfolwick.com |access-date=2015-12-23 |archive-date=2016-03-04 |archive-url=https://web.archive.org/web/20160304134437/http://www.tobyfolwick.com/tx750/textual/cm1289.php |url-status=dead }}</ref>
* 1977 [[Honda CB400]] SOHC 6-valve parallel-twin.
* 1978 [[Honda CX series|Honda CX500]], a 498 cc SOHC, pushrod actuated OHV, 4-valve per cylinder V-twin; 1982 [[Honda CX500#CX500 Turbo|CX500 Turbo]] was the first factory multi-valve [[
* 1978 [[Honda CBX1000]], a 1,047 cc DOHC 24-valve straight-6 ({{Convert|105|bhp|kW PS|0|abbr=on}}).
* 1979 -1992: [[Honda NR|Honda NR series]], racing & production motorcycles with '''8-valve-per-cylinder''' "oval-piston" V4 engines (actually 32-valve V8s with adjoining cylinders merged).
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[[Ettore Bugatti]] designed several multi-valve aircraft engines. The 1916 [[Bugatti U-16]] 1484.3 cid (24.32 L) SOHC 16-cylinder, consisting of two parallel 8-cylinder banks, offered 410 bhp (305 kW) at 2,000 rpm (12.5 kW/liter or 0.28 bhp/cid). Each cylinder had two vertical inlet valves and a single vertical exhaust valve, all driven by rocking levers from the camshaft. Other advanced [[World War I]] aircraft engines, such as the 1916 [[Maybach Mb.IVa]] that produced {{Convert|300|bhp|kW PS|0|abbr=on}} at altitude and the 1916 [[Benz Bz.IV]] with aluminium pistons and the 1918 [[Napier Lion]] (a 450 bhp 24-liter DOHC 12-cylinder), used two intake valves and two exhaust valves.
Long after the King-Bugatti "U-16" aviation engine used them, shortly before World War II, the [[Junkers]] aviation firm began production of the Third Reich's most-produced military aviation engine (68,000+ produced), the 1936-designed, 35-litre displacement, inverted-V12, liquid-cooled [[Junkers Jumo 211]], which used a three-valve cylinder head design<ref>[http://www.enginehistory.org/German/Jumo%20211/j26.jpg German language
The [[V12 engine]]s of many [[World War II]] fighter aircraft used a SOHC configuration with four valves for each cylinder.
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== Boats ==
In 1905 car builder [[Delahaye]] had experimented with a [[DOHC]] marine racing engine with six valves per cylinder. This Delahaye '''Titan''' engine was a massive 5190 cid (85.0-liter) four-cylinder that produced 350 bhp (0.07 bhp/cid). It allowed the motor boat ''Le Dubonnet'' piloted by [[Emile Dubonnet]] to set a new world's speed record on water, reaching {{Convert|33.80|mi/h|km/h|abbr=on}} on the lake at [[Juvisy]], near [[Paris]], [[France]].<ref>{{cite book |url=https://books.google.com/books?id=w07kz8QiXygC |title=Classic Speedboats 1916–1939 (Motorbooks International, 1997, p.16, ISBN 0-7603-0464-5) |author=Gérald Guétat |access-date=2011-12-23 |isbn=9780760304648 |date=1998-01-10 }}</ref>
An example of modern multi-valve engines for small boats is the [[Volvo Penta|Volvo Penta IPS Series]]. These joystick-operated seawater-cooled inboard diesel engines use combined charging (turbo and supercharger, except IPS450) with aftercooler, common rail fuel injection and DOHCs with hydraulic 4-valve technology. Propshaft power ranges from {{Convert|248|to|850|bhp|kW PS|0|abbr=on}} (highest efficiency 59.7 kW/liter for IPS400 3.7-liter straight-4 diesel). Multiple units can be combined.
== References ==
<ref name=fuel>In direct injection engines - such as diesels and later petrol engines - fuel is delivered to the chamber directly via the injector rather than through a valve. In carburetted engines and indirect-injection engines the fuel is mixed with the air outside of the cylinder and both enter together via the intake valve.
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