Bosch designed the direct injection fuel system on the new Duramax 6600 engine. The Bosch common rail fuel injection system maximizes power for each pulse of fuel into the engine. It produces less heat, which allows the engine to generate more power and burn fuel more completely.

• Direct fuel injection evenly distributes fuel throughout the system, from injector to injector. It creates more power for each injector pulse than indirect injection.
   
   
• For the first time, pressure generation is decoupled from and independent of engine speed.
   
   
• The direct injection system can be programmed for optimal performance over the entire engine speed range. This means new levels of fuel efficiency, emissions and driving comfort under all conditions.
   

• The fuel is drawn from the tank by the low-pressure pump through the Electronic Driver Unit (EDU). The fuel cools the electronics, which actuate solenoid valves in each injector, sometimes over 25 times per second.
   
   
• The EDU works with the Engine Control Module (ECM) to provide a strong, precise signal for each cylinder's combustion event. The ECM also controls pressure in the fuel rail to ensure that it will be correct for precise fuel metering.
   
   
• From the EDU, the fuel passes through an engine-mounted fuel filter. This filter has a water sensor, a water separator and a fuel heater. If necessary, the heater warms the fuel to 57 degrees Fahrenheit to prevent any waxing of the fuel.
   
   
• The fuel then goes to the Bosch high-pressure pump. If the ECM and EDU are the brains of the system, the Bosch high-pressure pump is the heart. It sends the fuel to the fuel rails, variably controlled at pressures up to 23,000 psi, where it is distributed to the injectors at each cylinder.
   
   
• The injector, with a constant injection pressure fed to it, can now open, stay open and close as directed by the ECM and EDU, depending on various sensor inputs, to achieve effective combustion for the conditions present.
   
   
• The injector is optimally located in the cylinder head, and configured with a custom-designed spray pattern matching the combustion chamber, to gain the most efficient combustion. This enables improved fuel efficiency, lower emissions, and less heat loss and rejection.
   
   

• The sophistication and technology of the direct injection system components make the Duramax engine capable of employing a process known as "pilot injection."
   
   
• Pilot injection involves injecting a small amount of fuel into the cylinder prior to the main injection event. A complex process in the electronic controls selects the optimal time, duration and quantity of pilot injection, coupled with the main injection charges.
   
   
• The result — combustion starts on a smaller scale and builds subtly, but rapidly, for reduced noise/knock, less vibration and quieter and smoother warm-ups.