Common rail
Overview
 
Common rail direct fuel injection is a modern variant of direct fuel injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....

 system for petrol
Petrol engine
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels....

 and diesel engine
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...

s.

On diesel engines, it features a high-pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 (over 1000 bar (14,503.8 psi)) fuel rail
Fuel rail
A fuel rail is essentially a pipe used to deliver fuel to individual fuel injectors on internal combustion engines. It is designed to have a pocket or seat for each injector as well as an inlet for a fuel supply. Some fuel rails also incorporate an attached fuel pressure regulator...

 feeding individual solenoid valve
Solenoid valve
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports...

s, as opposed to low-pressure fuel pump
Fuel pump
A fuel pump is a frequently essential component on a car or other internal combustion engined device. Many engines do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank through a line or hose to the engine...

 feeding unit injectors
Unit Injector
Unit Injector is an integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component...

 (Pumpe/Düse or pump nozzles). Third-generation common rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to 1800 bar (26,106.8 psi).

In gasoline engines
Petrol engine
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels....

, it is used in gasoline direct injection
Gasoline direct injection
In internal combustion engines, gasoline direct injection , also known as petrol direct injection or direct petrol injection, is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines...

 engine technology.
The common rail system prototype was developed in the late 1960s by Robert Huber of Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 and the technology further developed by Dr.
Encyclopedia
Common rail direct fuel injection is a modern variant of direct fuel injection
Fuel injection
Fuel injection is a system for admitting fuel into an internal combustion engine. It has become the primary fuel delivery system used in automotive petrol engines, having almost completely replaced carburetors in the late 1980s....

 system for petrol
Petrol engine
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels....

 and diesel engine
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...

s.

On diesel engines, it features a high-pressure
Pressure
Pressure is the force per unit area applied in a direction perpendicular to the surface of an object. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure.- Definition :...

 (over 1000 bar (14,503.8 psi)) fuel rail
Fuel rail
A fuel rail is essentially a pipe used to deliver fuel to individual fuel injectors on internal combustion engines. It is designed to have a pocket or seat for each injector as well as an inlet for a fuel supply. Some fuel rails also incorporate an attached fuel pressure regulator...

 feeding individual solenoid valve
Solenoid valve
A solenoid valve is an electromechanical valve for use with liquid or gas. The valve is controlled by an electric current through a solenoid: in the case of a two-port valve the flow is switched on or off; in the case of a three-port valve, the outflow is switched between the two outlet ports...

s, as opposed to low-pressure fuel pump
Fuel pump
A fuel pump is a frequently essential component on a car or other internal combustion engined device. Many engines do not require any fuel pump at all, requiring only gravity to feed fuel from the fuel tank through a line or hose to the engine...

 feeding unit injectors
Unit Injector
Unit Injector is an integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component...

 (Pumpe/Düse or pump nozzles). Third-generation common rail diesels now feature piezoelectric injectors for increased precision, with fuel pressures up to 1800 bar (26,106.8 psi).

In gasoline engines
Petrol engine
A petrol engine is an internal combustion engine with spark-ignition, designed to run on petrol and similar volatile fuels....

, it is used in gasoline direct injection
Gasoline direct injection
In internal combustion engines, gasoline direct injection , also known as petrol direct injection or direct petrol injection, is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines...

 engine technology.

History

The common rail system prototype was developed in the late 1960s by Robert Huber of Switzerland
Switzerland
Switzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....

 and the technology further developed by Dr. Marco Ganser at the Swiss Federal Institute of Technology
ETH Zurich
The Swiss Federal Institute of Technology Zurich or ETH Zürich is an engineering, science, technology, mathematics and management university in the City of Zurich, Switzerland....

 in Zurich
Zürich
Zurich is the largest city in Switzerland and the capital of the canton of Zurich. It is located in central Switzerland at the northwestern tip of Lake Zurich...

, later of Ganser-Hydromag AG (est.1995) in Oberägeri
Oberägeri
Oberägeri, until 1798 simply known as Ägeri, is a municipality in the canton of Zug in Switzerland.-History:Oberägeri is first mentioned in 1150 as Agregia. In 1538 it was mentioned as Ober Egere....

.

The first successful usage in production vehicle began in Japan
Japan
Japan is an island nation in East Asia. Located in the Pacific Ocean, it lies to the east of the Sea of Japan, China, North Korea, South Korea and Russia, stretching from the Sea of Okhotsk in the north to the East China Sea and Taiwan in the south...

 by the mid-1990s. Dr. Shohei Itoh and Masahiko Miyaki of the Denso Corporation, a Japanese automotive parts manufacturer, developed the common rail fuel system for heavy duty vehicles and turned it into practical use on their ECD-U2 common-rail system mounted on the Hino Rising Ranger truck and sold for general use in 1995. Denso claims the first commercial high pressure common rail system in 1995.

Modern common rail systems, whilst working on the same principle, are governed by an engine control unit
Engine control unit
An engine control unit is a type of electronic control unit that determines the amount of fuel, ignition timing and other parameters an internal combustion engine needs to keep running...

 (ECU) which opens each injector electronically rather than mechanically. This was extensively prototyped in the 1990s with collaboration between Magneti Marelli, Centro Ricerche Fiat and Elasis. After research and development
Research and development
The phrase research and development , according to the Organization for Economic Co-operation and Development, refers to "creative work undertaken on a systematic basis in order to increase the stock of knowledge, including knowledge of man, culture and society, and the use of this stock of...

 by the Fiat Group
Fiat
FIAT, an acronym for Fabbrica Italiana Automobili Torino , is an Italian automobile manufacturer, engine manufacturer, financial, and industrial group based in Turin in the Italian region of Piedmont. Fiat was founded in 1899 by a group of investors including Giovanni Agnelli...

, the design was acquired by the German company Robert Bosch GmbH
Robert Bosch GmbH
Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...

 for completion of development and refinement for mass-production. In hindsight the sale appeared to be a tactical error for Fiat as the new technology proved to be highly profitable. The company had little choice but to sell, however, as it was in a poor financial state at the time and lacked the resources to complete development on its own. In 1997 they extended its use for passenger cars. The first passenger car that used the common rail system was the 1997 model Alfa Romeo 156
Alfa Romeo 156
The Alfa Romeo 156 is a compact executive car introduced by Italian automaker Alfa Romeo at the 1997 Frankfurt Motor Show as the replacement for the Alfa Romeo 155...

 2.4 JTD
JTD engine
JTD , an initialism for uniJet Turbo Diesel, is Fiat Group's term for its current common rail turbodiesel engine range. The MultiJet name is used in the second generation JTD common rail units. Most of the Fiat, Alfa Romeo and Lancia range has JTD engines...

, and later on that same year Mercedes-Benz C 220 CDI.

Common rail engines have been used in marine and locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...

 applications for some time. The Cooper-Bessemer GN-8 (circa 1942) is an example of a hydraulically operated common rail diesel engine, also known as a modified common rail.

Vickers used common rail systems in submarine engines circa 1916. Doxford Engines Ltd
William Doxford & Sons
William Doxford & Sons Ltd, often referred to simply as Doxford, was a British shipbuilding company.-History:The Company was established by William Doxford in 1840. From 1870 it was based in Pallion, Sunderland, on the River Wear in Northeast England. The Company was managed by William Doxford's...

. (opposed piston heavy marine engines) used a common rail system (from 1921 to 1980) whereby a multi-cylinder reciprocating fuel pump generated a pressure of approximately 600bar with the fuel being stored in accumulator bottles. Pressure control was achieved by means of an adjustable pump discharge stroke and a "spill valve". Camshaft operated mechanical timing valves were used to supply the spring-loaded Brice/CAV/Lucas injectors which injected through the side of the cylinder into the chamber formed between the pistons. Early engines had a pair of timing cams, one for ahead running and one for astern. Later engines had two injectors per cylinder and the final series of constant pressure turbocharged engines were fitted with four injectors per cylinder. This system was used for the injection of both diesel oil and heavy fuel oil (600cSt heated to a temperature of approximately 130°C).

The common rail system is suitable for all types of road cars with diesel engines, ranging from city car
City car
A city car is a small car intended for use primarily in an urban area.City cars are sold worldwide and most automotive industry manufacturers have one or two in their line-up. In North-America city cars are often referred to simply as "subcompacts" alongside the superminis. These kind of cars...

s such as the Fiat Nuova Panda to executive car
Executive car
Executive car is a British term that refers to a car's size and is used to describe an automobile larger than a large family car. In official use, the term is adopted by EuroNCAP, a European organisation founded to test car safety.- History :...

s such as the Audi A6
Audi A6
The Audi A6 is an executive car marketed by the German automaker Audi AG, now in its fourth generation. As the successor to the Audi 100, the A6 is manufactured in Neckarsulm, Germany – and is available in saloon, and wagon configurations, the latter marketed by Audi as the Avant.All generations...

.

Common rail today

Today the common rail system has brought about a revolution in diesel engine technology. Robert Bosch GmbH
Robert Bosch GmbH
Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...

, Delphi Automotive Systems, Denso Corporation, and Siemens VDO
Siemens VDO
VDO , is a manufacturer of information and cockpit systems, navigation, telematics, communication and audio systems, and control and fuel systems....

 (now owned by Continental AG) are the main suppliers of modern common rail systems. The car makers refer to their common rail engines by their own brand
Brand
The American Marketing Association defines a brand as a "Name, term, design, symbol, or any other feature that identifies one seller's good or service as distinct from those of other sellers."...

 names:
  • BMW
    BMW
    Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...

    's D-engines (also used in the Land Rover
    Land Rover
    Land Rover is a British car manufacturer with its headquarters in Gaydon, Warwickshire, United Kingdom which specialises in four-wheel-drive vehicles. It is owned by the Indian company Tata Motors, forming part of their Jaguar Land Rover group...

     Freelander TD4)
  • Cummins
    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...

     and Scania's XPI (Developed under joint venture)
  • Cummins
    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...

     CCR (Cummins
    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...

     pump with Bosch
    Robert Bosch GmbH
    Robert Bosch GmbH is a multinational engineering and electronics company headquartered in Gerlingen, near Stuttgart, Germany. It is the world's largest supplier of automotive components...

     Injectors)
  • Daimler's CDI (and on Chrysler
    Chrysler
    Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....

    's Jeep
    Jeep
    Jeep is an automobile marque of Chrysler . The first Willys Jeeps were produced in 1941 with the first civilian models in 1945, making it the oldest off-road vehicle and sport utility vehicle brand. It inspired a number of other light utility vehicles, such as the Land Rover which is the second...

     vehicles simply as CRD)
  • Fiat Group
    Fiat
    FIAT, an acronym for Fabbrica Italiana Automobili Torino , is an Italian automobile manufacturer, engine manufacturer, financial, and industrial group based in Turin in the Italian region of Piedmont. Fiat was founded in 1899 by a group of investors including Giovanni Agnelli...

    's (Fiat
    Fiat
    FIAT, an acronym for Fabbrica Italiana Automobili Torino , is an Italian automobile manufacturer, engine manufacturer, financial, and industrial group based in Turin in the Italian region of Piedmont. Fiat was founded in 1899 by a group of investors including Giovanni Agnelli...

    , Alfa Romeo
    Alfa Romeo
    Alfa Romeo Automobiles S.p.A. is an Italian manufacturer of cars. Founded as A.L.F.A. on June 24, 1910, in Milan, the company has been involved in car racing since 1911, and has a reputation for building expensive sports cars...

     and Lancia
    Lancia
    Lancia Automobiles S.p.A. is an Italian automobile manufacturer founded in 1906 by Vincenzo Lancia and which became part of the Fiat Group in 1969. The company has a long history of producing distinctive cars and also has a strong rally heritage. Some modern Lancias are seen as presenting a more...

    ) JTD
    JTD engine
    JTD , an initialism for uniJet Turbo Diesel, is Fiat Group's term for its current common rail turbodiesel engine range. The MultiJet name is used in the second generation JTD common rail units. Most of the Fiat, Alfa Romeo and Lancia range has JTD engines...

    (also branded as MultiJet, JTDm, Ecotec CDTi, TiD, TTiD, DDiS, Quadra-Jet)
  • Ford Motor Company
    Ford Motor Company
    Ford Motor Company is an American multinational automaker based in Dearborn, Michigan, a suburb of Detroit. The automaker was founded by Henry Ford and incorporated on June 16, 1903. In addition to the Ford and Lincoln brands, Ford also owns a small stake in Mazda in Japan and Aston Martin in the UK...

    's TDCi Duratorq and Powerstroke
  • General Motors
    General Motors
    General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...

     Opel
    Opel
    Adam Opel AG, generally shortened to Opel, is a German automobile company founded by Adam Opel in 1862. Opel has been building automobiles since 1899, and became an Aktiengesellschaft in 1929...

     CDTI and earlier DTI
  • General Motors
    General Motors
    General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...

     Chevrolet
    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...

     VCDi (licensed from VM Motori
    VM Motori
    VM Motori S.p.A. is a diesel engine manufacturing company in Cento, Italy, in Emilia-Romagna, an Italian region which is also home to Ferrari, Lamborghini, Maserati and Ducati.- History :...

    ; also branded as Ecotec CDTI)
  • Honda
    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...

    's i-CTDi
  • Hyundai-Kia
    Hyundai Kia Automotive Group
    The Hyundai Kia Automotive Group is South Korea's largest automobile manufacturer, the second largest automaker in Asia after Toyota and the world's fourth largest automaker after Toyota, GM, and Volkswagen as of the end of 2010...

    's CRDi
  • IKCO's EFD
    IKCO EF engines
    IKCO EF engines are four cylinders engines. The EF7 series are designed jointly by Iran Khodro Powertrain Company and F.E.V GmbH of Germany. The other models will be designed by IPCO itself. IPCO is the powertrain designing & producing company of Iranian car manufacturer Iran Khodro...

    which is one of the members of the EF family. Supplier TBD
  • Isuzu
    Isuzu
    , is a Japanese car, commercial vehicle and heavy truck manufacturing company, headquartered in Tokyo. In 2005, Isuzu became the world's largest manufacturer of medium to heavy duty trucks. It has assembly and manufacturing plants in the Japanese city of Fujisawa, as well as in the prefectures...

    's iTEQ
  • Komatsu
    Komatsu
    orKomatsu is a multinational corporation that manufactures construction, mining, and military equipment, Industrial equipments such as press machines, lasers, and thermoelectric generators.Its headquarters is at 2-3-6, Akasaka, Minato, Tokyo, Japan...

    's Tier3, Tier4, 4D95 and higher - HPCR series Diesel engines.
  • Mahindra's CRDe
  • Mazda
    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...

    's MZR-CD (1.4 MZ-CD, 1.6 MZ-CD manufactured by joint venture Ford/PSA Peugeot Citroën
    PSA Peugeot Citroën
    PSA Peugeot Citroën is a French manufacturer of automobiles and motorcycles sold under the Peugeot and Citroën marques. Headquartered in the 16th arrondissement of Paris, PSA is the second largest automaker based in Europe and the number eight in the world.-History:In December 1974 Peugeot S.A....

    ) and earlier DiTD
  • 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...

    's DI-D (recently developed 4N1 engine
    Mitsubishi 4N1 engine
    The Mitsubishi 4N1 engine is a family of all-alloy four-cylinder diesel engines developed by Mitsubishi Motors, produced at the company's powertrain facility in Kyoto, Japan for use in Mitsubishi's small to mid-sized global passenger cars....

     family uses next generation 200 MPa (2000 bar) injection system))
  • Nissan's dCi
    DCI
    -Technology:* D-chiro-inositol, an isomer of inositol* Data, Context, and Interaction, an architectural pattern in computer software development* Direct Count & Intersect, an algorithm for discovering frequent sets in large databases...

    , Infiniti uses dCi engines, but not branded as dCi.
  • Proton's SCDi
  • PSA Peugeot Citroën
    PSA Peugeot Citroën
    PSA Peugeot Citroën is a French manufacturer of automobiles and motorcycles sold under the Peugeot and Citroën marques. Headquartered in the 16th arrondissement of Paris, PSA is the second largest automaker based in Europe and the number eight in the world.-History:In December 1974 Peugeot S.A....

    's HDI or HDi
    HDI
    HDI may refer to:* Human Development Index, a United Nations measure of well-being in a country* PSA HDi engine, a diesel automobile engine by Peugeot/Citroën* Hexamethylene diisocyanate, an organic compound used to make polymers such as polyurethane...

    (1.4HDI, 1.6 HDI, 2.0 HDI, 2.2 HDI and V6 HDI developed under joint venture with Ford)
  • Renault
    Renault
    Renault S.A. is a French automaker producing cars, vans, and in the past, autorail vehicles, trucks, tractors, vans and also buses/coaches. Its alliance with Nissan makes it the world's third largest automaker...

    's dCi
    DCI
    -Technology:* D-chiro-inositol, an isomer of inositol* Data, Context, and Interaction, an architectural pattern in computer software development* Direct Count & Intersect, an algorithm for discovering frequent sets in large databases...

    and earlier dTi
  • SsangYong
    SsangYong Motor Company
    SsangYong Motor Company is the fourth largest South Korean automobile manufacturer. The name SsangYong means double dragons.SsangYong was acquired by India's Mahindra & Mahindra Limited in February 2011, after being named the preferred bidder in 2010 to acquire the bankruptcy-protected company...

    's XDi (most of these engines are manufactured by Daimler AG)
  • Subaru
    Subaru
    ; is the automobile manufacturing division of Japanese transportation conglomerate Fuji Heavy Industries .Subaru is internationally known for their use of the boxer engine layout popularized in cars by the Volkswagen Beetle and Porsche 911, in most of their vehicles above 1500 cc as well as...

    's Legacy TD (as of Jan 2008)
  • Tata
    Tata Motors
    Tata Motors Limited is an Indian multinational automotive corporation headquartered in Mumbai, India. Part of the Tata Group, it was formerly known as TELCO...

    's DICOR & CR4
  • Toyota's D-4D
  • Volkswagen Group
    Volkswagen Group
    Volkswagen Group is a German multinational automobile manufacturing group. , Volkswagen was ranked as the world’s third largest motor vehicle manufacturer and Europe's largest....

    : The 6.0 V12 TDI
    Turbocharged Direct Injection
    TDI or Turbocharged Direct Injection is a design of turbodiesel engines, which feature turbocharging and cylinder-direct fuel injection, developed and produced by Volkswagen Group. These TDI engines are widely used in all mainstream Volkswagen Group marques of passenger cars and light commercial...

    , 4.2 TDI (V8), 2.7 and 3.0 TDI (V6), 1.6, 2.0 TDI (L4) and 1.2 TDI (L3) engines featured on current Seat, Skoda, VW and Audi models use common rail, as opposed to the earlier unit injector
    Unit Injector
    Unit Injector is an integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component...

     engines.
  • Volvo
    Volvo
    AB Volvo is a Swedish builder of commercial vehicles, including trucks, buses and construction equipment. Volvo also supplies marine and industrial drive systems, aerospace components and financial services...

     2.4D and D5 engines (1.6D, 2.0D manufactured by Ford and PSA Peugeot Citroen
    PSA Peugeot Citroën
    PSA Peugeot Citroën is a French manufacturer of automobiles and motorcycles sold under the Peugeot and Citroën marques. Headquartered in the 16th arrondissement of Paris, PSA is the second largest automaker based in Europe and the number eight in the world.-History:In December 1974 Peugeot S.A....

    ), Volvo Penta
    Volvo Penta
    Volvo Penta was founded in 1907 in conjunction with the production of the first marine engine, B1. The Penta company soon became an established internal combustion engine manufacturer, which in 1927 delivered the engine to Volvo's first passenger car....

     D-serie engines
  • Wärtsilä-Sulzer 14RT-flex96-C
    Wärtsilä-Sulzer RTA96-C
    The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is currently considered the largest reciprocating engine in the world, designed for large container ships, running on heavy fuel oil...

     "largest reciprocating engine in the world" designed by the Finnish
    Finland
    Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

     manufacturer Wärtsilä
    Wärtsilä
    Wärtsilä is a Finnish corporation which manufactures and services power sources and other equipment in the marine and energy markets. The core products of Wärtsilä include large combustion engines...


Principles

Solenoid or piezoelectric valves make possible fine electronic control
Electronic control unit
In automotive electronics, electronic control unit is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle....

 over the fuel injection time and quantity and the higher pressure that the common rail technology makes available provides better fuel atomisation. In order to lower engine noise, the engine's electronic control unit
Electronic control unit
In automotive electronics, electronic control unit is a generic term for any embedded system that controls one or more of the electrical systems or subsystems in a motor vehicle....

 can inject a small amount of diesel just before the main injection event ("pilot" injection), thus reducing its explosiveness and vibration, as well as optimising injection timing and quantity for variations in fuel quality, cold starting and so on. Some advanced common rail fuel systems perform as many as five injections per stroke.

Common rail engines require very short (< 1 s) or no heating up time at all and produce lower engine noise and emissions than older systems.

Diesel engines have historically used various forms of fuel injection. Two common types include the unit injection system and the distributor/inline pump systems (See diesel engine
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...

 and unit injector
Unit Injector
Unit Injector is an integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component...

 for more information). While these older systems provided accurate fuel quantity and injection timing control, they were limited by several factors:
  • They were cam driven and injection pressure was proportional to engine speed. This typically meant that the highest injection pressure could only be achieved at the highest engine speed and the maximum achievable injection pressure decreased as engine speed decreased. This relationship is true with all pumps, even those used on common rail systems; with the unit or distributor systems, however, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator and thus the relationship is more prominent and troublesome.
  • They were limited in the number and timing of injection events that could be commanded during a single combustion event. While multiple injection events are possible with these older systems, it is much more difficult and costly to achieve.
  • For the typical distributor/inline system, the start of injection occurred at a pre-determined pressure (often referred to as: pop pressure) and ended at a pre-determined pressure. This characteristic resulted from "dummy" injectors in the cylinder head which opened and closed at pressures determined by the spring preload applied to the plunger in the injector. Once the pressure in the injector reached a pre-determined level, the plunger would lift and injection would start.


In common rail systems, a high pressure pump stores a reservoir of fuel at high pressure — up to and above 2000 bars (29,007.5 psi). The term "common rail" refers to the fact that all of the fuel injectors are supplied by a common fuel rail which is nothing more than a pressure accumulator where the fuel is stored at high pressure. This accumulator supplies multiple fuel injectors with high pressure fuel. This simplifies the purpose of the high pressure pump in that it only has to maintain a commanded pressure at a target (either mechanically or electronically controlled). The fuel injectors are typically ECU-controlled. When the fuel injectors are electrically activated, a hydraulic valve (consisting of a nozzle and plunger) is mechanically or hydraulically opened and fuel is sprayed into the cylinders at the desired pressure. Since the fuel pressure energy is stored remotely and the injectors are electrically actuated, the injection pressure at the start and end of injection is very near the pressure in the accumulator (rail), thus producing a square injection rate. If the accumulator, pump and plumbing are sized properly, the injection pressure and rate will be the same for each of the multiple injection events.

See also

  • Gasoline Direct Injection
    Gasoline direct injection
    In internal combustion engines, gasoline direct injection , also known as petrol direct injection or direct petrol injection, is a variant of fuel injection employed in modern two-stroke and four-stroke gasoline engines...

  • Unit Injector
    Unit Injector
    Unit Injector is an integrated direct fuel injection system for diesel engines, combining the injector nozzle and the injection pump in a single component...

  • Unit pump
  • Turbocharged Direct Injection
    Turbocharged Direct Injection
    TDI or Turbocharged Direct Injection is a design of turbodiesel engines, which feature turbocharging and cylinder-direct fuel injection, developed and produced by Volkswagen Group. These TDI engines are widely used in all mainstream Volkswagen Group marques of passenger cars and light commercial...

  • Fuel filter
    Fuel filter
    A fuel filter is a filter in the fuel line that screens out dirt and rust particles from the fuel, normally made into cartridges containing a filter paper. They are found in most internal combustion engines....

  • Water sensor
    Water sensor
    The Water in Fuel Sensor or WiF sensor indicates the presence of water in the fuel. It is installed in the fuel filter and when the water level in the water separator reaches the warning level, the Wif send an electrical signal to the ECU or to dashboard ....

  • Air flow sensor

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