# Common rail

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Engine fuel delivery method

For other uses, see [Common rail (disambiguation)](/source/Common_rail_(disambiguation)).

Diesel fuel injector as installed in a MAN V8 Diesel engine

**Common rail direct fuel injection** is a direct [fuel injection](/source/Fuel_injection) system built around a high-[pressure](/source/Pressure) fuel rail feeding [solenoid valves](/source/Solenoid_valve). This pressure is typically over 2,000 [bar](/source/Bar_(unit)) or 200 [MPa](/source/Pascal_(unit)) or 29,000 [psi](/source/Pound_per_square_inch). A common rail system contrasts with the low-pressure [fuel pump](/source/Fuel_pump_(engine)) feeding [unit injectors](/source/Unit_Injector) (or pump nozzles). High-pressure injection delivers power and fuel consumption benefits over earlier lower pressure fuel injection,[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] by injecting fuel as a larger number of smaller droplets, giving a much higher ratio of surface area to volume. This provides improved vaporization from the surface of the fuel droplets, and so more efficient combining of atmospheric oxygen with vaporized fuel delivering more complete [combustion](/source/Combustion).

Common rail injection is widely used in [diesel engines](/source/Diesel_engine). It is also the basis of [gasoline direct injection](/source/Gasoline_direct_injection) systems used on [petrol engines](/source/Petrol_engine).

## History

Common rail fuel system on a Volvo truck engine

In 1916 [Vickers](/source/Vickers) pioneered the use of mechanical common rail systems in [G-class submarine](/source/British_G-class_submarine) engines. For every 90° of rotation, four plunger pumps allowed a constant injection pressure of 3,000 pounds per square inch (210 bar; 21 MPa), with fuel delivery to individual cylinders being shut off by valves in the injector lines.[1] From 1921 to 1980 [Doxford Engines](/source/William_Doxford_%26_Sons) used a common rail system in their [opposed-piston marine engines](/source/Opposed-piston_engine), where a multicylinder reciprocating fuel pump generated a pressure around 600 bars (60 MPa; 8,700 psi), with fuel stored in accumulator bottles.[2] Pressure control was achieved by 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 was fitted with four. This system was used for the injection of both diesel and heavy fuel oil (600cSt heated to a temperature near 130 °C).

Common rail engines have been used in marine and [locomotive](/source/Locomotive) applications for some time. The [Cooper-Bessemer](/source/Cooper_Bessemer) GN-8 (*circa* 1942) is an example of a hydraulically operated common rail diesel engine, also known as a modified common rail.

The common rail system prototype for automotive engines was developed in the late 1960s by [Robert Huber](/source/Robert_Huber_(engineer)) of Switzerland, and the technology was further developed by Dr. Marco [Ganser](https://en.wikipedia.org/w/index.php?title=GANSER_CRS_AG&action=edit&redlink=1) at the [Swiss Federal Institute of Technology](/source/ETH_Zurich) in Zurich, later of [Ganser-Hydromag AG](https://en.wikipedia.org/w/index.php?title=Ganser_CRS_AG&action=edit&redlink=1) (est. 1995) in Oberägeri.

The first common-rail-Diesel-engine used in a road vehicle was the MN 106-engine by East German *[VEB](/source/Volkseigener_Betrieb) IFA Motorenwerke Nordhausen*. It was built into a single [IFA W50](/source/IFA_W_50) in 1985. Due to a lack of funding, the development was cancelled and mass production was never achieved.[3]

The first successful mass production vehicle with common rail, was sold in Japan in 1995. Dr. Shohei Itoh and Masahiko Miyaki of the [Denso Corporation](/source/Denso_Corporation) developed the ECD-U2 common rail system, mounted on the [Hino Ranger](/source/Hino_Ranger#3rd_Generation_.281989-2002.29) truck.[4] Denso claims the first commercial high-pressure common rail system in 1995.[5]

Modern common rail systems are governed by an [engine control unit](/source/Engine_control_unit), which controls injectors electrically rather than mechanically. Prototyped in the 1990s by [Magneti Marelli](/source/Magneti_Marelli), Centro Ricerche Fiat in [Bari](/source/Bari), and Elasis, with further development by physicist Mario Ricco [Fiat Group](/source/Fiat). Unfortunately Fiat were in a poor financial state at this time, so the design was acquired by [Robert Bosch GmbH](/source/Robert_Bosch_GmbH) for refinement and mass production.[6] The first passenger car to use this system was the 1997 [Alfa Romeo 156](/source/Alfa_Romeo_156) with a 2.4-L [JTD engine](/source/JTD_engine),[7] and later that same year, [Mercedes-Benz](/source/Mercedes-Benz) introduced it in their [W202](/source/Mercedes-Benz_C-Class_(W202)) model. In 2001, common rail injection made its way into pickup trucks with the introduction of the 6.6 liter Duramax LB7 V8 used in the Chevrolet Silverado HD and GMC Sierra HD. In 2003 Dodge and Cummins launched common rail engines, and Ford followed in 2008 with the 6.4L Powerstroke. Today almost all non-commercial diesel vehicles use common rail systems.

## Applications

The common rail system is suitable for all types of road cars with diesel engines, ranging from [city cars](/source/City_car) (such as the [Fiat Panda](/source/Fiat_Panda#Second_generation_(169;_2003))) to [executive cars](/source/Executive_car) (such as the [Audi A8](/source/Audi_A8)). The main suppliers of modern common rail systems are [Bosch](/source/Robert_Bosch_GmbH), [Delphi Technologies](/source/Delphi_Technologies), [Denso](/source/Denso), and [Siemens VDO](/source/Siemens_VDO) (now owned by [Continental AG](/source/Continental_AG)).[8]

## Acronyms and branding used

Bosch common rail diesel fuel injector from a Volvo truck engine

The automotive manufacturers refer to their common rail engines by their own [brand](/source/Brand) names:

- [Ashok Leyland](/source/Ashok_Leyland): **CRS** (used in U Truck and E4 Busses)

- [Audi](/source/Audi): **[TDI](/source/TDI_(engine))**, **BiTDi** The "Bi" stands for [BiTurbo](/source/Twin-turbo)

- [BMW Group](/source/BMW_Group) ([BMW](/source/BMW) and [Mini](/source/Mini)): **d** (also used in the [Land Rover Freelander](/source/Land_Rover_Freelander) as TD4 and the [Rover 75](/source/Rover_75) and [MG ZT](/source/MG_ZT) as CDT and CDTi), **D** and **SD**

- [Chrysler](/source/Chrysler) **CRD**

- [Citroën](/source/Citro%C3%ABn): **[HDi](/source/HDi)**, **e-HDi** and **BlueHDi**

- [Cummins](/source/Cummins) and [Scania](/source/Scania_(company)): **XPI** (developed under joint venture)

- [Cummins](/source/Cummins): **CCR** ([Cummins](/source/Cummins) pump with [Bosch](/source/Robert_Bosch_GmbH) injectors)

- [Daimler](/source/Daimler_AG): **CDI**

- [Fiat Group](/source/Fiat) ([Fiat](/source/Fiat), [Alfa Romeo](/source/Alfa_Romeo) and [Lancia](/source/Lancia)): **[JTD](/source/JTD_engine)** (also branded as **MultiJet**, **JTDm**, and by supplied manufacturers as **TDi**, **CDTi**, **TCDi**, **TiD**, **TTiD**, **DDiS** and **QuadraJet**)

- [Ford Motor Company](/source/Ford_Motor_Company): **TDCi** ([Duratorq](/source/Duratorq) and [Powerstroke](/source/Powerstroke)) and **EcoBlue Diesel**

- [GM](/source/General_Motors): **VCDi** (licensed from [VM Motori](/source/VM_Motori)) **Duramax Diesel**, **Diesel** and **CTDI**

- [Honda](/source/Honda): **i-CTDI** and **i-DTEC**

- [Hyundai](/source/Hyundai_Motor_Company), [Kia](/source/Kia_Motors) and [Genesis](/source/Genesis_Motor): **CRDi**

- [IKCO](/source/IKCO): **[EFD](/source/IKCO_EF_engines)**

- [Isuzu](/source/Isuzu): **iTEQ**, **Ddi** and **DI TURBO**

- [Jaguar](/source/Jaguar_Cars): **d**

- [Jeep](/source/Jeep): **CRD** and **[EcoDiesel](/source/EcoDiesel)**

- [Komatsu](/source/Komatsu_Limited): **Tier3**, **Tier4**, **4D95** and higher ***HPCR***-series

- [Land Rover](/source/Land_Rover): **TD4**, eD4, SD4, TD6, TDV6, SDV6, TDV8, SDV8

- [Lexus](/source/Lexus): **d** (e.g. 450d and 220d)

- [Mahindra](/source/Mahindra_%26_Mahindra): **CRDe**, **m2DiCR**, **mEagle**, **mHawk**, **mFalcon** and **mPower (Trucks)**

- [Maserati](/source/Maserati): **Diesel**

- [Mazda](/source/Mazda): **MZR-CD** and **Skyactiv-D** (some MZR-CD engines are manufactured by the [Ford](/source/Ford_Motor_Company) and [PSA Peugeot Citroën](/source/PSA_Peugeot_Citro%C3%ABn) joint venture) and earlier **DiTD**

- [Mercedes-Benz](/source/Mercedes-Benz): **CDI** and **d**

- [Mitsubishi](/source/Mitsubishi_Motors): **Di-D**

- [Nissan](/source/Nissan): **DDTi**

- [Opel](/source/Opel)/[Vauxhall](/source/Vauxhall_Motors): **DTI**, **CDTI**, **BiTurbo CDTI**, **CRI**, **Turbo D** and **BiTurbo D**

- [Porsche](/source/Porsche): **Diesel**

- [Proton](/source/Proton_(carmaker)): **SCDi**

- [Groupe PSA (Peugeot, Citroën and DS)](/source/Groupe_PSA): **HDi**, **e-HDi** or **BlueHDi** (developed under joint venture with [Ford](/source/Ford_Motor_Company)) – See [PSA HDi engine](/source/PSA_HDi_engine)

- [Renault](/source/Renault), [Dacia](/source/Automobile_Dacia) and [Nissan](/source/Nissan_Motor_Company): **dCi** and **BLUEdCi** (Infiniti uses some dCi engines as part of the [Renault-Nissan Alliance](/source/Renault%E2%80%93Nissan%E2%80%93Mitsubishi_Alliance), branded **d**)

- [Saab](/source/Saab_Automobile): **TiD** (The 2.2 turbo diesel engine was also called "TiD", but it didn't have Common rail) and **TTiD** The double "T" stands for [Twin-Turbo](/source/Twin-turbo)

- [SsangYong](/source/SsangYong_Motor_Company): **XDi**, eXDI, **XVT** or **D**

- [Subaru](/source/Subaru): **TD**, **D** or **BOXER DIESEL** (as of Jan 2008)

- [Suzuki](/source/Suzuki): **DDiS**

- [Tata](/source/Tata_Motors): **2.2 VTT DiCOR** (used in large SUV-class such as [Safari](/source/Tata_Safari)), **VARICOR** (used in large SUV-class such as [Safari Storme](/source/Tata_Safari_Storme), [Aria](/source/Tata_Aria) and [Hexa](/source/Tata_Hexa)),**1.05 Revotorq CR3** (used in [Tiago](/source/Tata_Tiago) and [Tigor](/source/Tata_Tigor)) **1.5 Revotorq CR05** (used in [Nexon](/source/Tata_Nexon) and [Altroz](/source/Tata_Altroz)), **1.4 CR4** (used in [Indica](/source/Tata_Indica), [Indigo](/source/Tata_Indigo)), **3.0 CR4** (used in [Sumo gold](/source/Tata_Sumo)**) 1.3 Quadrajet** (supplied by [Fiat](/source/Fiat) and used in [Indica Vista](/source/Indica_Vista), [Indigo Manza](/source/Tata_Indigo_Manza) and [Zest](/source/Tata_Zest)), and **2.0 Kryotec** (also supplied by Fiat and used in SUV [Harrier](/source/Tata_Harrier) and All new [Safari](/source/Tata_Safari)),**3.3 L Turbotronn** and **5L Turbotronn** ( used in M&HCV Trucks).

- [Toyota](/source/Toyota): **D4-D**

- [Volkswagen Group](/source/Volkswagen_Group) ([Volkswagen](/source/Volkswagen), [Audi](/source/Audi), [SEAT](/source/SEAT) and [Škoda](/source/%C5%A0koda_Auto)): **[TDI](/source/Turbocharged_Direct_Injection)** (more recent models use common rail, as opposed to the earlier [unit injector](/source/Unit_Injector) engines). Bentley term their Bentayga diesel simply **Diesel**

- [Volvo](/source/Volvo): **D**, **D2**, **D3**, **D4** and **D5** engines (some are manufactured by [Ford](/source/Ford_Motor_Company) and [PSA Peugeot Citroën](/source/PSA_Peugeot_Citro%C3%ABn)), [Volvo Penta](/source/Volvo_Penta) D-series engines

## Principles

Diagram of the common rail system

Solenoid or [piezoelectric](/source/Piezoelectric) valves make possible fine [electronic control](/source/Electronic_control_unit) over the fuel-injection time and quantity, and the higher pressure that the common rail technology makes available provides better fuel [atomisation](/source/Aerosol). To lower engine [noise](/source/Noise_(environmental)), the engine's electronic control unit 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.[9]

Common rail engines require a very short to no heating-up time, depending on the ambient temperature, and produce lower engine noise and emissions than older systems.[10]

Diesel engines have historically used various forms of fuel injection. Two common types include the [unit-injection](/source/Unit_injector) system and the [distributor/inline-pump systems](/source/Injection_pump). While these older systems provide accurate fuel quantity and injection timing control, they are limited by several factors:

- They are cam driven, and injection pressure is proportional to engine speed. This typically means that the highest injection pressure can only be achieved at the highest engine speed and the maximum achievable injection pressure decreases as engine speed decreases. This relationship is true with all pumps, even those used on common rail systems. With unit or distributor systems, the injection pressure is tied to the instantaneous pressure of a single pumping event with no accumulator, thus the relationship is more prominent and troublesome.

- They are limited in the number and timing of injection events that can 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 occurs at a predetermined pressure (often referred to as pop pressure) and ends at a predetermined pressure. This characteristic results from "dumb" injectors in the cylinder head which open and close at pressures determined by the spring preload applied to the plunger in the injector. Once the pressure in the injector reaches a predetermined level, the plunger lifts and injection starts.

In common rail systems, a high-pressure pump stores a reservoir of fuel at high pressure—up to and above 2,000 bars (200 MPa; 29,000 psi). The term "common rail" refers to the fact that all of the [fuel injectors](/source/Fuel_injector) 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 needs to maintain a target pressure (either mechanically or electronically controlled). The fuel injectors are typically controlled by the [engine control unit](/source/Engine_control_unit) (ECU). 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.

Third-generation[*[vague](https://en.wikipedia.org/wiki/Wikipedia:Vagueness)*] common rail diesels now feature [piezoelectric](/source/Piezoelectric) injectors for increased precision, with fuel pressures up to 2,500 bar (250 MPa; 36,000 psi).[11]

## See also

- [Hydraulically actuated electronic unit injection](/source/Unit_injector)

- [Unit pump](/source/Unit_pump)

- [Water sensor](/source/Water_sensor)

## References

1. **[^](#cite_ref-1)** Cummins, C. Lyle (2007). *Diesels for the First Stealth Weapon*. Carnot Press. pp. 196–198. [ISBN](/source/ISBN_(identifier)) [978-0-917308-06-2](https://en.wikipedia.org/wiki/Special:BookSources/978-0-917308-06-2).

1. **[^](#cite_ref-2)** ["Doxford Engine Reference"](https://www.doxford-engine.com/engines.htm). [Archived](https://web.archive.org/web/20071220213443/http://doxford-engine.com/engines.htm) from the original on 2007-12-20.

1. **[^](#cite_ref-3)** ["Nordhäuser an Entwicklung des weltweit ersten Common-Rail-Diesels beteiligt – IFA-Museum öffnet zur Nordhäuser Museumsnacht"](https://web.archive.org/web/20201028135442/https://meinanzeiger.de/nordhausen/nordhaeuser-an-entwicklung-des-weltweit-ersten-common-rail-diesels-beteiligt-ifa-museum-oeffnet-zur-nordhaeuser-museumsnacht/). meinanzeiger.de. 25 March 2015. Archived from [the original](https://meinanzeiger.de/nordhausen/nordhaeuser-an-entwicklung-des-weltweit-ersten-common-rail-diesels-beteiligt-ifa-museum-oeffnet-zur-nordhaeuser-museumsnacht/) on 2020-10-28. Retrieved 2022-03-03.

1. **[^](#cite_ref-4)** ["240 Landmarks of Japanese Automotive Technology - Common rail ECD-U2"](https://web.archive.org/web/20090908165507/http://www.jsae.or.jp/autotech/data_e/10-8e.html). Jsae.or.jp. Archived from [the original](http://www.jsae.or.jp/autotech/data_e/10-8e.html) on 2009-09-08. Retrieved 2009-04-29.

1. **[^](#cite_ref-5)** ["Diesel Fuel Injection"](http://www.globaldensoproducts.com/em/dem/crs/index.html). *DENSO Global*. [Archived](https://web.archive.org/web/20110807070253/http://www.globaldensoproducts.com/em/dem/crs/index.html) from the original on 2011-08-07. Retrieved 2011-08-03.

1. **[^](#cite_ref-economist.com_6-0)** ["Fiat Rebirth of a carmaker"](http://www.economist.com/opinion/displaystory.cfm?story_id=11090197). *economist.com*. 2008-04-24. [Archived](https://web.archive.org/web/20090908034030/http://www.economist.com/opinion/displaystory.cfm?story_id=11090197) from the original on 2009-09-08. Retrieved 2008-05-01.

1. **[^](#cite_ref-autonews.com_7-0)** ["New Powertrain Technologies Conference"](https://web.archive.org/web/20130703105445/http://www.autonews.com/files/07_ane_ptc/speakers.html). *autonews.com*. Archived from [the original](http://www.autonews.com/files/07_ane_ptc/speakers.html) on 2013-07-03. Retrieved 2008-04-08.

1. **[^](#cite_ref-8)** ["Denso targets French, US automakers : World's No. 4 supplier will grow organically, not by acquisitions"](http://europe.autonews.com/article/20051017/ANE/510170842/denso-targets-french-us-automakers). *Europe.autonews.com*. 2005-10-17. Retrieved 16 May 2018.

1. **[^](#cite_ref-9)** (multistroke injection) See BMW 2009 Brochure for 3 series

1. **[^](#cite_ref-10)** ["Archived copy"](https://web.archive.org/web/20180514134251/http://www.carservicesalisbury.com/go/common-rail-diesel-service%7D). *www.carservicesalisbury.com*. Archived from [the original](http://www.carservicesalisbury.com/go/common-rail-diesel-service%7D) on 14 May 2018. Retrieved 15 January 2022.{{[cite web](https://en.wikipedia.org/wiki/Template:Cite_web)}}: CS1 maint: archived copy as title ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_archived_copy_as_title))

1. **[^](#cite_ref-11)** ["DENSO Develops a New Diesel Common Rail System With the World's Highest Injection Pressure| News | DENSO Global Website"](http://www.globaldenso.com/en/newsreleases/130626-01.html). *DENSO Global Website*. 2013-06-26. [Archived](https://web.archive.org/web/20171013221631/http://www.globaldenso.com/en/newsreleases/130626-01.html) from the original on 2017-10-13.

## External links

Wikimedia Commons has media related to [Common rail fuel injection](https://commons.wikimedia.org/wiki/Category:Common_rail_fuel_injection).

- [Common Rail Direct Injection System or CRDI System working and advantages](https://www.enggstudy.com/common-rail-direct-injection-system)

- [Brief Summary about working of CRDI Engine](https://crankit.in/common-rail-direct-injection-crdi/)

- [Animation explaining common rail functioning](https://www.youtube.com/watch?v=aGwV9ueHcz4)

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v t e Engine configurations for piston engines Type Atmospheric Axial Beam Cornish Rotative Bourke Cam engine Camless Compound Double-acting cylinder Flathead Free-piston Stelzer Hemi Heron head Intake over exhaust Oscillating cylinder Opposed-piston Overhead camshaft Overhead valve Pentroof Rotary Single-acting cylinder Split cycle Swing-piston Uniflow Watt Wedge Stroke cycle Two-stroke Four-stroke Five-stroke Six-stroke Two-and four-stroke Cylinder layout Inline – straight I1 I2 I3 I4 I5 I6 I7 I8 I9 I12 I14 Flat – boxer F2 F4 F6 F8 F10 F12 F16 V – vee V2 V3 V4 V5 VR5 V6 VR6 V8 V10 V12 V14 V16 V18 V20 V24 W W3 W6 W8 W12 W16 W18 W24 W30 Deltic H Radial Split-single U X

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Adapted from the Wikipedia article [Common rail](https://en.wikipedia.org/wiki/Common_rail) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Common_rail?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.