Diesel SystemsCommon Rail Systems CRSN4 with 2,100 to 2,500 bar with pressure amplifier

In addition to increasingly ambitious emission targets, economic efficiency and further reduction of fuel con-sumption are the main drivers in commercial-vehicle diesel engine development. The pressure-amplified Bosch system CRSN4-21 has been in series production since 2007.

The system increases the customer’s freedom in flex-ible rate shaping, which means lower fuel consump-tion, compliance with US10 and Euro VI and optimum driveability and combustion noise at the same time.

Higher injection pressures can be utilized to gain further fuel combustion benefits, thereby reducing CO2 output. This is why we complemented the com-mercial-vehicle Common Rail System portfolio with the CRSN4-25 which has an increased system pressure of up to 2,500 bar. The platform of the series-produced CRSN4-21 has been evolutionarily developed for higher injection pressure, maximum injection quantities and increased system efficiency. Series production of the CRSN4-25 started in 2012.

Exhaust gas recirculation is employed to reduce the formation of nitrogen oxides. Related combustion methods require highest injection pressures in order to limit particle mass emission. Common Rail Systems achieve high injection pressures even at part load, since system pressure is virtually independent from engine speed.

The pressure-amplified CRSN4 offers the possibility to select the injection rate in a flexible way at start of injection, thereby reducing the formation of nitrogen oxides in the area of the NOx sensitive engine map. This allows engine applications with optimized fuel efficiency. The achievable operating-cost benefit compared to equivalent engines in the market is outstanding: While optimizing an engine with the pressure-amplified CRSN4, significant fuel-con-sumption benefits can be achieved under real load conditions.

Customer benefits Optimization of fuel consumption at peak

torque operation points and minimization of raw emissions through flexible rate shaping (“Boot”, “Ramp”, “Square”)

Reduced number of injector parts affected by peak pressure; pump and rail as well as high-pressure lines only have to be designed for a pressure of up to 900 bar (CRSN4-21) or 1,200 bar (CRSN4-25)

Lower fuel consumption resulting in a corresponding reduction in CO2 output

Contribution toward achieving emission limits such as Euro VI, US10, JPNLT

Maximum flexibility for adaptation to engines with particulate filter and/or Denoxtronic system

Pressure limit. valve

High-pressure pump

Tank with pre-filter

ActuatorsSensors

Rail

Filter

Rail-pressure sensor

Injector

Control unit

Common Rail System CRSN4-25

Possible applicationsThe CRSN4 is used for heavy-duty applications.

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Functional principleThe pressure-amplified CRSN4-25 with its two actua-tors offers fully flexible rate shaping. Using multiple pre-injections, “Boot”, “Ramp”, and “Square” rate shapes for main injection as well as several post injections, the ideal injection curve can be realized for every operating point. This enables optimal perform ance data with minimal fuel consumption and low emissions.

System designThe high-pressure pump CPN5-12/2 with two pistons generates pressures between 250 and 1,200 bar. The pump is lubricated by fuel. This prevents oil leaking into the fuel circuit and increasing emissions.

The high-pressure rail LWRN-12 is designed in the length of the heavy-duty engine. This allows the use of short high-pressure lines with reduced pressure oscillations.

The maximum system pressure of up to 2,500 bar is generated by the hydraulic pressure amplifier inte-grated into the injector CRIN4-25. This means that a minimal number of injector parts is affected by peak pressure. The rest of the system operates at the lower, non-amplified system pressure of up to 1,200 bar. The injector consists of injection module, pressure-amplifi-er module, and control module. The injection and control modules each have a separate actuator. Pre-, main- and post-injections are controlled by the injec-tion module. The pressure amplifier is activated by the control module as required.

Diesel Systems | Common Rail Systems CRSN4 with 2,100 to 2,500 bar with pressure amplifier

Technical features: CRSN4-25System pressure 250–2,500 bar

Max. number of injections 5

Rate shape Boot, Ramp, Square

Operating voltage 12 V/24 V

Max. injection quantity Full load: 492 mm3/stroke (Boot) > 1,050 erpm Rated point: 444 mm3/stroke (Square) @ 1,800 erpm

Hydr. flow rate 570–870 cm3/30s

Applications HD, OHW

Emission target Euro V, Euro VI, US10, JPNLT

Engine cylinders 4–6

Engine displacement 1.7–2.6 l/cyl.

Max. engine power 90 kw/cyl.

High-pressure pump CPN5-12/2

High-pressure rail LWRN-12

CRIN4-25 injector

Components: CRSN4-25

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