In automotive engineering
Automotive engineering
Modern automotive engineering, along with aerospace engineering and marine engineering, is a branch of vehicle engineering, incorporating elements of mechanical, electrical, electronic, software and safety engineering as applied to the design, manufacture and operation of motorcycles, automobiles,...

 a multi-valve or multivalve engine is one where each cylinder has more than two valves
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...

. A multi-valve engine has better breathing and can operate at higher revolutions per minute
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...

 (RPM) than a two-valve engine, delivering more power.

Multi-valve rationale

A multi-valve design typically has three, four, or five valves
Poppet valve
A poppet valve is a valve consisting of a hole, usually round or oval, and a tapered plug, usually a disk shape on the end of a shaft also called a valve stem. The shaft guides the plug portion by sliding through a valve guide...

 per cylinder to achieve improved performance. Any four-stroke internal combustion engine
Internal combustion engine
The internal combustion engine is an engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber. In an internal combustion engine, the expansion of the high-temperature and high -pressure gases produced by combustion apply direct force to some component of the engine...

 needs at least two valves per cylinder: one for intake of air and fuel, and another for exhaust of combustion gases. Adding more valves increases valve area and improves the flow of intake and exhaust gases, thereby enhancing combustion, volumetric efficiency, and power output. Multi-valve geometry allows the spark plug to be ideally located within the combustion chamber for optimal flame propagation. Multi-valve engines tend to have smaller valves that have lower reciprocating mass, which can reduce wear on each cam lobe, and allow more power from higher RPM without the danger of valve bounce
Valve float
Valve float is an adverse condition which occurs when the poppet valves on an internal combustion engine valvetrain do not remain in contact with the camshaft lobe during the valve closure phase of the cam lobe profile...

. Some engines are designed to open each intake valve at a slightly different time, which increases turbulence, improving the mixing of air and fuel at low engine speeds. The disadvantages of multi-valve engines are an increase in manufacturing cost, and a potential increase in oil consumption due to the greater number of valve stem seals. Turbocharging and supercharging
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...

 are technologies that also improve engine breathing, and can be used instead of, or in conjunction with, multi-valve engines.
  • 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 a lower RPM limit. The manufacturing cost for this design can be lower than for a four-valve design. This design was common in the late 1980's and early 1990's, but has been largely superseded by four and five-valve designs.
  • Four-valve cylinder head

This is the most common type of multi-valve head, with two exhaust valves and two similar (or slightly larger) inlet valves. This design allows similar breathing as compared to a three-valve head, and as the small exhaust valves allow high RPM, this design is very suitable for high power outputs.
  • 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, and as every valve is small, high RPM and very high power outputs are available. It has been questioned whether a five-valve configuration gives a worthwhile benefit over four-valve designs.
In theory, a five-valve design should have a higher maximum RPM, but and the three inlet ports should give both good cylinder-filling and high turbulence (both desirable traits). After making the five-valve Genesis engine for several years, Yamaha
Yamaha Motor Company
, is a Japanese motorized vehicle-producing company. Yamaha Motor is part of Yamaha Corporation and its headquarter is located in Iwata, Shizuoka. Along with expanding Yamaha Corporation into the world's biggest piano maker, then Yamaha CEO Genichi Kawakami took Yamaha into the field of motorized...

 returned to the more cost-effective four-valve design.

Cars and trucks

An early example was the 1912 Peugeot
Peugeot is a major French car brand, part of PSA Peugeot Citroën, the second largest carmaker based in Europe.The family business that precedes the current Peugeot company was founded in 1810, and manufactured coffee mills and bicycles. On 20 November 1858, Emile Peugeot applied for the lion...

. Starting in 1922, many Bugatti
Automobiles E. Bugatti was a French car manufacturer founded in 1909 in Molsheim, Alsace, as a manufacturer of high-performance automobiles by Italian-born Ettore Bugatti....

 engines used three valves per cylinder actuated by a single overhead camshaft (SOHC) and multi-valve engines continued to be popular in racing and sports engines.

The first mass-produced car using four valves per cylinder was the British Triumph Dolomite
Triumph Dolomite
The Triumph Dolomite was a popular small saloon car produced by the Triumph Motor Company division of the British Leyland Corporation in Canley, Coventry between October 1972 and August 1980.-History:...

 Sprint of 1973 which used a chain-driven SOHC 16-valve engine (four valves per cylinder) producing 127 bhp. Such engines soon became common as Japanese manufacturers adopted the multi-valve concept. Nissan's 1988-1992 SOHC KA24E
Nissan KA engine
The KA engines were a series of inline-4 four-stroke gasoline piston engines manufactured by Nissan, which were offered in 2.0 L and 2.4 L versions.The engines blocks were made of cast-iron, while the cylinder heads were made of aluminum....

 engine had three valves per cylinder (two intakes, one exhaust). Nissan upgraded to the DOHC after 1992 for some of the sports cars, including the 240SX. Mercedes and Ford also produce three-valve V6 and V8 engines, Ford claiming an 80% improvement in high RPM breathing without the added cost of a DOHC valve train. The Ford design uses one spark plug per cylinder located in the centre, but the Mercedes design uses two spark plugs per cylinder located on opposite sides, leaving the centre free to add a direct-to-cylinder fuel injector at a later date.

Examples of SOHC four-valve engines include: the Honda
is a Japanese public multinational corporation primarily known as a manufacturer of automobiles and motorcycles.Honda has been the world's largest motorcycle manufacturer since 1959, as well as the world's largest manufacturer of internal combustion engines measured by volume, producing more than...

Honda F engine
The Honda F-Series engine was Honda's "big block" SOHC inline four, though lower production DOHC versions of the F-series were built. It features an aluminum open deck cast iron sleeved block and aluminum/magnesium cylinder head...

 engines, D-series
Honda D engine
The D series inline 4-cylinder engines have been used in a variety of compact Honda models, most commonly the Honda Civic, CRX, Logo, Stream, and first-generation Integra. Its displacement ranges between 1.2 and 1.7 liters and is available in both SOHC and DOHC versions; with some equipped with...

 engines, all J-series
Honda J engine
The J-series was Honda's second V6 engine family, introduced in 1996. It is a 60° V6 – Honda's existing C-series was a 90° engine. The J-series was designed for transverse mounting. It has a shorter bore spacing , shorter connecting rods, and a special smaller crankshaft than the C-series for...

 engines, the R-series
Honda R engine
The Honda R engine is an inline-four engine launched in 2006 for the Honda Civic . It is fuel injected, has an aluminum-alloy cylinder block and cylinder head, is a SOHC 16-valve design and utilizes Honda's i-VTEC system...

 engines, the Mazda
is a Japanese automotive manufacturer based in Fuchū, Aki District, Hiroshima Prefecture, Japan.In 2007, Mazda produced almost 1.3 million vehicles for global sales...

 B8-ME, the Chrysler 3.5 L V6 engine
Chrysler SOHC V6 engine
The single overhead cam V6 introduced in 1993 was a major advancement for Chrysler. It was derived from Chrysler's first homegrown front-wheel drive V6, the Chrysler 3.3 engine, and remains in production today. The SOHC V6 is likely to be replaced by the Chrysler Pentastar engine by 2013.There...

. The V12 engine
V12 engine
A V12 engine is a V engine with 12 cylinders mounted on the crankcase in two banks of six cylinders, usually but not always at a 60° angle to each other, with all 12 pistons driving a common crankshaft....

s of many World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 fighter aircraft also used a SOHC configuration with four valves for each cylinder.

Yamaha designed the cylinder head for the Toyota 4A-GE 20V Silvertop and Blacktop
Toyota A engine
The A Series engines are a family of straight-4 internal combustion engines with displacement from 1.3 L to 1.8 L produced by Toyota Motor Corporation...

 engine used in the MR2
Toyota MR2
The Toyota MR2 is a two-seat, mid-engined, rear wheel drive sports car produced by Central Motors, a part of Toyota, from 1984 until July 2007 when production stopped in Japan...

 and some Corollas
Toyota AE86
The AE86 generation of the Toyota Corolla Levin and Toyota Sprinter Trueno is a small, lightweight coupe introduced by Toyota in 1983 as part of the fifth generation Toyota Corolla lineup. For the purpose of brevity, the insider-chassis code of "AE86" is used to describe the whole range...

. Mitsubishi
Mitsubishi Motors
is a multinational automaker headquartered in Minato, Tokyo. In 2009 it was the fifth-largest Japan-based automaker and the 17th-largest in the world measured by production...

 were the first to market a car engine with five valves per cylinder, with the 548 cc 3G81 engine in their Minica Dangan ZZ kei car
Kei car
Kei cars, K-cars, or , are a Japanese category of small vehicles, including passenger cars, vans, and pickup trucks. They are designed to comply with Japanese government tax and insurance regulations, and in most rural areas are exempted from the requirement to certify that adequate parking is...

 in 1989.
Bugatti EB110
Bugatti EB110
The Bugatti EB110 is a mid-engine sports car from Bugatti Automobili SpA. It was unveiled on September 15, 1991, in both Versailles and in front of the Grande Arche at La Défense in Paris, France, exactly 110 years after Ettore Bugatti's birth....

, Ferrari F355
Ferrari F355
The Ferrari F355 is a sports car built by Ferrari from May 1994 to 1999. It is an evolution of the Ferrari 348 and was replaced by the Ferrari 360. It is a mid-engined, rear wheel drive V8-powered 2-seat coupe...

, Volkswagen
Volkswagen is a German automobile manufacturer and is the original and biggest-selling marque of the Volkswagen Group, which now also owns the Audi, Bentley, Bugatti, Lamborghini, SEAT, and Škoda marques and the truck manufacturer Scania.Volkswagen means "people's car" in German, where it is...

Audi AG is a German automobile manufacturer, from supermini to crossover SUVs in various body styles and price ranges that are marketed under the Audi brand , positioned as the premium brand within the Volkswagen Group....

-Skoda and Toyota have all produced five-valve engined vehicles.

Maserati is an Italian luxury car manufacturer established on December 1, 1914, in Bologna. The company's headquarters is now in Modena, and its emblem is a trident. It has been owned by the Italian car giant Fiat S.p.A. since 1993...

 made an experimental 2.0 L turbo-V6 engine with six valves per cylinder 1985 (three intakes, three exhaust).

Although most multi-valve engines have overhead camshaft
Overhead camshaft
Overhead cam valvetrain configurations place the engine camshaft within the cylinder heads, above the combustion chambers, and drive the valves or lifters in a more direct manner compared to overhead valves and pushrods...

s, either SOHC or DOHC; but a multivalve engine may be a pushrod overhead valve engine (OHV) design. Chevrolet
Chevrolet , also known as Chevy , is a brand of vehicle produced by General Motors Company . Founded by Louis Chevrolet and ousted GM founder William C. Durant on November 3, 1911, General Motors acquired Chevrolet in 1918...

 has revealed a three-valve version of its Generation IV V8
GM LS engine
The GM LS engine family is an engine design intended as the only V-8 engine used in General Motors' line of rear-wheel-drive cars and trucks. The LS series was a "clean sheet" design with little in common with the classic Chevrolet small block V8...

 which uses pushrods to actuate forked rockers, and Cummins
Cummins Inc. is a Fortune 500 corporation that designs, manufactures, distributes and services engines and related technologies, including fuel systems, controls, air handling, filtration, emission control and electrical power generation systems...

 makes a four-valve OHV straight six diesel
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...

, the Cummins B Series
Cummins B Series engine
The Cummins B Series is a family of straight-four and straight-6 diesel truck and industrial piston engines manufactured by Cummins. The B Series is known for displacing "one liter per cylinder" because of the popular straight-four and straight-six. A straight-four is also available...

 (now known as ISB).


Examples of motorcycles with multivalve-engines include:
  • 1929 Rudge-Whitworth  Ulster OHV 500 cc single cylinder machine.
  • 1972 Honda "pent-roof" XL250
    Honda XL250
    Honda XL250 is a four stroke 250cc motorcycle from Honda introduced in 1972 and manufactured through most of the 1980s. It's a renamed Honda SL250. When it appeared it was the first modern four stroke enduro motorcycle and the first mass-produced 4-valve motorcycle...

     SOHC single cylinder machine.
  • 1977 Honda three-valve SOHC CB400
    Honda CB400
    The Honda CB400 Super Four is a continuation of the Honda CB400 four. It is an all-rounder bike, sporty and suitable for learner riders where the low weight and ease of handling can help build riding confidence and ability. ABS brakes are an option on later models...

     twin cylinder machine.
  • 1978 Honda CX500
    Honda CX series
    The Honda CX series motorcycles, including the GL500 and GL650 variants, were developed and released by Honda in the late 1970s, with production ending in most markets by the mid 1980s...

    , an OHV four-valve V-twin.
  • 1979 -1992: Honda NR series
    Honda NR
    Honda's NR V-four motorcycle engine series started in 1979 with the 500cc NR500 Grand Prix racer that used oval pistons. This was followed during the 1980s by a 750cc endurance racer version known as the NR750. The oval piston concept allowed for eight valves per cylinder which generated more...

    , racing & production motorcycles with eight-valve "oval-piston" V4 engines.
  • 1985 Yamaha
    Yamaha Motor Company
    , is a Japanese motorized vehicle-producing company. Yamaha Motor is part of Yamaha Corporation and its headquarter is located in Iwata, Shizuoka. Along with expanding Yamaha Corporation into the world's biggest piano maker, then Yamaha CEO Genichi Kawakami took Yamaha into the field of motorized...

     DOHC five-valve "Genesis" Yamaha FZ750
    Yamaha FZ750
    The Yamaha FZ750 is a sport motorcycle produced by Yamaha Motor Corporation between 1985 and 1991. The FZ750 is notable as predecessor of the highly successful Yamaha FZR1000.- Development :...


The XT660 single once had five valves, but a subsequent redesign reduced the valve-count to four.

External links

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