Common Rail: features, advantages & disadvantages

Common Rail: features, advantages & disadvantages

Common Rail is a fuel supply system used in modern diesel cars. Its main feature is the use of a fuel rail common to all fuel injectors which serves as an accumulator where fuel is stored under high pressure (up to 300 mPa). Fuel is fed into the rail by a high-pressure pump. From there it is supplied to the injectors and is injected directly into the engine cylinders. The injection timing, fuel metering, and number of injections per cycle are controlled by the ECU.

The Common Rail system has been installed on passenger cars since 1997. Nowadays, diesel engines of most passenger and commercial vehicles are equipped with it.

Engines equipped with the Common Rail system

Car make Engine brand name Engine models
Nissan, Dacia, Renault dCi K9K, R9M, F9Q, R9N, M9R, G9T, G9U, M9T, P9X, V9X
Mercedes-Benz CDI OM646, OM611, OM651, OM647, OM612, OM648, OM668, OM628, OM629
d OM654, OM656
Opel, Vauxhall CRI, CRI BiTurbo X20DTL, Y20DTH, Z17DTL, Z17DTH, Z13DTH, Z19DTH
CDTi Z17DTH, A17DT, A13DTE, A17DTJ, Z17DTJ, G9U 630, A17DTR, A20DTH, Z13DTJ, Z13DTH, Z19DTH
BiTurbo CDTI A20DTR, B20DTR
Hyundai, KIA CRDi J3, D3FA, D4EB, D4CB, D4FC, D4FA, D4FB, D4FD, D4EA, D4HB, D6EA, G6EN, D3EA
Land Rover ED4 204DTD
TD4 224DT, DW12BTED4, 204D3, M47
TDV8 448DT, 368DT
TD6 276DT
TDV6 306DT
SDV6 30DDTX
SDV8 448DT
SD4 224DT
Citroën, Peugeot, DS, Volvo HDI, HDi DV4TD, DV4TED4, DV6TED4, DV6ATED4, DV6ETED, DW10TD
BlueHDi, e-HDi RHE (DW10CTED4), BHY (DV6FD), BHX (DV6FC), DV6FCTED, DW10FCTED4, DW10FC, DW10FDTED4, DV6FETED, DV6FE, DV5TED4
Fiat, Alfa Romeo, Lancia JTD 182 B4.000, 188 A2.000, 185 A6.000, 839 A5.000, 186 A6.000, 182 B4.000, 182 B9.000, AR 34202, AR 32501, 937 A2.000
JTDm 955 A4.000, 955 A3.000, 198 A2.000, 939 A7.000, 937 A6.000
MultiJet 188 A8.000, 188 A9.000, 198 A3.000, 199 B1.000, 263 A1.000
Audi, Škoda, Volkswagen, Seat TDI CVMD, CAAC, DCXA, DBGC, DFGA, CLJA, CBAB,CAYC, BKS, BMK, CASA, CJMA, CRCA, CDUD, CKDA, DCZA
BiTDi CDCA, CNEA, CSHA
Isuzu DDi iTEQ 4JJ1
Chevrolet, Daewoo VCDi Z20S, Z20DMH, LLW, Z20S1, Z20D1, Z22D1
Honda i-DTEC N16A, N16A2, N22B1, N16A3, N22B3, N22B4
i-CTDi N22A1, N22A3
CTDI N22A2
Mazda MZR-CD RF7J, R2AA, RF5C, RF7J, Y601, Y642
Skyactiv-D S5-DPTS, S8-DPTS, SH-VPTS
D SHY1
CiTD RF5C
DI Turbo Y601
Mitsubishi DI-D 4N13, 4N14, 4N15
SsangYong XDi D20DT, D27DT
eXDI D20DTF
XVT D27DTP
Volvo Drive-E D4204T8, D4204T14, D4204T23, D 4162 T
D2 D5204T7, D4162T
D3 D5204T5
D4 D4204T5, D5204T
D5 D5244T, D5244T5, D5244T15, D 5244 T9
Chrysler, Jeep CRD ENC, ENJ, ENS, ENR, EXF, EXA, ENE, ENF, EXL
BMW, MINI d N47 D20 C, N57 D30 A, N57 D30 B, B37 C15 A
SD, D N47C20A
Ford TDCi F6JB, HHJC, UGJC, XVJA, XVJC, T1WB, QYBA, KHBA, T8CC, T1GA
Duratorq-TDCi DV4TD, F6JA, F6JB, DV4TED4
Saab TiD Z19DT, Z19DTH, D223L
TTiD A19DTR, Z19DTR, A 20 DTR
Toyota D-4D 1ND-TV, 1WW, 1AD-FTV, 2KD-FTV
D-CAT 2AD-FHV
Porsche Diesel M05.9E, M05.9D, MCU.DB, MCN.RB, MCR.CA, MCR.C, MCU.DC
Infinity d V9X, OM651
Subaru D EE20Z

Main components of the Common Rail system

Item No. Name Function
1 Low pressure fuel pump Located in the fuel tank. Supplies fuel to the high-pressure pump.
2 Fuel filter Removes dirt and various impurities from fuel and prevents the pump and injectors from wear.
3 High-pressure fuel pump Feeds fuel under pressure into the fuel rail.
4 Fuel metering valve Adjusts the amount of fuel fed to the high-pressure fuel pump.
5 Fuel pressure sensor Measures the pressure in the fuel rail and sends a corresponding signal to the ECU.
6 Fuel rail Contains fuel under high pressure.
7 Fuel pressure control valve Relieves excess pressure in the fuel rail. This valve returns excess fuel back to the fuel tank. It is controlled by the ECU.
8 Injectors Meter and spray fuel into the combustion chambers.

Advantages and disadvantages of Common Rail engines

Advantages Disadvantages
🟢 Fuel efficiency 🔴 Highly sensitive to fuel quality
🟢 Eco-friendliness 🔴 Injectors are sensitive to impurities
🟢 Quiet operation 🔴 Expensive and complicated repair
🟢 High torque 🔴 Fuel filters need to be replaced more frequently
🟢 High power output  

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