Mechanics of a Diesel Fuel Injection System

All diesel engines mounted on automobiles are generally four stroke engines. A four stroke engine operates by a constant repetition of the following sequence:

1. Intake stroke
2. Compression stroke;
3. Combustion (power) stoke;
4. Exhaust stroke

SUPPLY PUMP

The supply pump pressurizes fuel up to 1,800 bar and sends it to the common rail. The fuel pressure in the common rail is detected by the high-pressure sensor and controlled by adjusting an electromagnetic valve of the supply pump.

Product Types:

• HP-3 (for passenger cars and light-duty vehicles)
• HP-4 (for medium-duty vehicles)
• HP-0 (for heavy-duty vehicles, available up to 1,600 bar)

Benefits and Features:

• Generates high fuel pressure up to 1,800 bar
  • Adapting an outer cam structure rather than an inner cam structure reduces the surface pressure applied to the sliding part of the plunger that pressurizes fuel.
  • The plunger is made of a newly developed material with very little foreign matter and the sliding part of the plunger is coated with a ceramic material, improving fatigue limit of the plunger.
• Light weight
  • Using aluminum for pump housing parts that are not exposed to high pressure achieves the world's lightest supply pump for the common rail system.
• Precise control of fuel pressure in the common rail
  • The supply pump sends only a required amount of fuel to the common rail through the electromagnetic valve, precisely controlling the fuel pressure in the common rail.

SOLENOID INJECTOR

DENSO's solenoid injector can inject fuel at an interval of 0.4 milliseconds with a required small quantity -- only one cubic millimeter per pilot injection. The injectors allow the system to perform five injections during each combustion stroke. DENSO's proprietary technologies in material development and processing enabled the solenoid injector to achieve high performance with a fatigue strength sufficient for 1,800 bar injection pressure.

The five-time multiple injections are named "pilot," "pre," "main," "after, and "post" injections, respectively. The "pilot" injection, well before ignition, provides time for fuel and air to mix. The subsequent "pre" injection shortens ignition delay in the main injection and thereby reduces the generation of NOx, noise and vibration. The "after" injection, which happens a split-second after the main injection, re-burns any remaining PM. Then, the "post" injection helps manage the temperature of the exhaust gas, which makes the exhaust processing in the after-treatment system more effective.