Compared with the emissions of gasoline engines, diesels have typically offered benefits, particularly in hydrocarbons and carbon monoxide. But controlling nitrogen oxides (NOx) and particulate matter have been challenging. New emission regulation changes in the U.S., Canada and Europe require substantial NOx reduction. Meeting these new requirements by engine hardware changes alone has proven to be extremely difficult. However, the advanced aftertreatment technologies of the new Duramax diesel engines (Fig. 5) have shown great effectiveness in dealing with these emissions.
Two new Duramax diesel engines were developed to meet the 2010 Federal emission standards for oxides of nitrogen (NOx) and particulate matter (PM). They reduce NOx to 0.2 grams per brake horsepower per hour (g/bhp-hr). The 2007 standard was 1.2 (g/bhp-hr).
Engine Applications
The 6.6L Duramax diesel engine (RPO LGH, VIN code L) is used on 2010 interim and 2011 Chevrolet Express and GMC Savana vans and 2011 Chevrolet Silverado and GMC Sierra trucks with RPO ZW9 (chassis cabs or trucks with pickup box delete).
The 6.6L Duramax diesel engine (RPO LML, VIN code 8) is used on 2011 Chevrolet Silverado and GMC Sierra pickup models.
Mechanical Features
These engines use an iron block and aluminum cylinder heads. The bore and stroke are unchanged. The main bearing has been changed to enhance oil film thickness, and oil pump flow is increased.
In the cooling system, the thermostat is equipped with bleed holes to improve bleeding air from the system. The thermostat must be positioned with the bleed holes oriented toward the front of the engine. (Fig. 6)
(Fig. 6)
An oval air filter is used on vans and a flat panel air filter is used on pickups. Also on pickups, the charge air cooler system has plastic lock rings on the inlet and outlet ducts. Twist the lock ring counterclockwise to release the tabs.
A single variable nozzle turbocharger (VNT) is used. The oil feed has been relocated from the number 4 cam bearing to a dedicated supply port at the left rear of the engine valley.
The EGR valve and stepper motor are contained in one unit. The position sensor now reflects the true position of the valve -- the valve moves when the stepper motor extends or retracts.
A single EGR cooler is used on the LGH engine for Express and Savana van applications, and a dual cooler is used on the LGH engine for Silverado and Sierra truck applications. The LML engine for the pickups also uses a dual cooler with an EGR cooler bypass controlled by the ECM to prevent coking of the EGR cooler during light load and idling.
Fuel System Features
The fuel system supply side is equipped with a fuel filter vacuum switch near the fuel filter. The switch opens if there is a restriction on the supply side, indicated by a vacuum of 13.6 - 15 Hg.
The fuel system high pressure side uses a two-chamber pump that generates 200 megaPascals (mPa) of pressure (29,000 psi). Two high pressure lines feed the right fuel rail. A transfer tube carries fuel to the left fuel rail. A Fuel Rail Pressure sensor (FRP) is located on the rear of the left fuel rail.
The high pressure pump is timed so the peak pressure pulses match the injection events. Matching the pressure pulses results in a more constant pressure within the fuel rails. If the pump is removed, it must be retimed when it is installed. There are timing marks on the pump gear and camshaft gear that must be aligned.
Two Fuel Rail Pressure Regulators (FRPR) are used. FRPR 1 is still located on the injection pump as on previous Duramax engines. FRPR 2 is located on the front of the left fuel rail. This solenoid is normally open. The ECM supplies pulse width modulation to change the duty cycle of FRPR 2 to control the amount of fuel returned to the fuel tank.
The new Duramax engines are equipped with Bosch piezoelectric fuel injectors. These injectors operate at high voltage, indicated by the orange color of the injector harness. (Fig. 7)
(Fig. 7)
Do not make contact with the fuel injector harness, ECM or fuel injectors while the ignition is in the On or Run position. Use certified, insulated Class 0 gloves rated at 1000 volts. Remember to check the expiration date of the gloves.
The ECM supplies high voltage and provides a ground. Voltage is supplied up to 160 volts at 20 amps, and can peak up to 240 volts. This causes the injector to open. The capacitor discharges through an injector for initial opening and holds open with 12 volts.
Injectors are grouped into four pairs: 1-4, 6-7, 2-5, and 3-8. If a condition is detected in a group, that group is disabled and a DTC is set.
Piezoelectric injector features include: (Fig. 8)
A. Nozzle
B. Control valve
C. Hydraulic amplifier
D. Piezo actuator
E. High pressure supply
(Fig. 8)
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