In today's diesel engines, electronically controlled fuel injection systems have become the standard. These systems can be implemented in two main ways: one is to enhance the electronic control of the traditional fuel injection pump, governor, and timing device; the other is to adopt a completely new fuel injection concept, where the injector is directly controlled by an electronic system.
1. Electronically Controlled Inline Fuel Injection Pump
The electronically controlled inline fuel injection pump has evolved to include multiple functions such as fuel quantity and injection timing control. Some advanced systems also allow for the regulation of injection pressure and rate. The fuel quantity control is typically managed through an electronic governor, which allows for more precise and faster response compared to mechanical or electro-hydraulic governors. This makes it suitable for a wide range of applications. Different types of electronic governors exist, including purely electronic models like the RED-type from Japan’s DKK, the E-type from Germany’s Heinzmann, and the Barber Colmann system, as well as electro-hydraulic governors such as the ESR type from Bosch.
The injection timing in these systems often uses electro-hydraulic actuators, such as the ECS system from MTU (Germany), the ECD-P3 from Denso, and the PEEC system from Caterpillar (USA). Japan’s ZEXEL developed the TICS system, which uses a sliding sleeve mechanism to adjust the plunger’s pre-stroke, thus controlling the fuel supply timing. Komatsu also introduced a variable pre-stroke KP2 injection pump with a unique combined plunger design, while Bosch developed the RP39 and RP43 pumps, which are similar in structure to ZEXEL’s system.
2. Electronic Unit Pump (EUP) System
Bosch’s EUP system uses a short high-pressure fuel line to achieve higher injection pressures, up to 160 MPa. It utilizes high-speed solenoid valves to precisely control both the timing and amount of fuel injected.
3. Electronically Controlled Distributor Pump
In distributor pumps, fuel quantity and timing are usually controlled via high-speed solenoid valves. For example, Toyota’s ECD-type VE pump and Audi’s electronically controlled distributor pump use this approach. Stanadyne developed the DS-type distributor pump for GM’s 6.5L turbocharged engine in the 1990s, achieving a maximum injection pressure of 100 MPa. The newer RS-type pump can reach up to 140 MPa.
4. Electronically Controlled Pump Nozzle System
As emission and noise regulations become stricter, future truck engines will require injection pressures of around 150 MPa. Major automakers are developing high-pressure electronic fuel injection systems, such as the pump nozzle system. These systems can be either mechanically driven or accumulator-based, enabling better atomization and reduced turbulence in the combustion chamber.
5. Mechanically Driven Electronically Controlled Pump Nozzle
The most advanced systems are the mechanically driven ones, such as the DDEC from Detroit Diesel, the PDE27 and PDE28 from Bosch, and the EUI from Lucas CAV. Existing models already reach 150 MPa, and research engines have achieved up to 200 MPa. These systems are widely used across various engine sizes, from small to heavy-duty engines.
6. Electronically Controlled Accumulator Pump Nozzle
Recent developments focus on accumulator-based systems, which eliminate the need for mechanical drives. Caterpillar’s HEUI system, for example, combines electronic and hydraulic control to manage injection timing and pressure independently of engine speed. It can maintain high injection pressure up to 150 MPa and offers improved emissions and performance. BKM started developing these systems in 1975, and they are now used in engines ranging from 17 kW to 2910 kW, with injection pressures up to 160 MPa. Other notable systems include Komatsu’s KOMPICS, Denso’s ECD-U2 common rail, and Bosch’s common rail accumulator system.
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