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Discussion in '07.5 - 2010 LMM' started by MAX4X4, May 5, 2008.

  1. MAX4X4

    MAX4X4 Recruit

    May 4, 2008
    2007 DURAMAX DIESEL 6.6L V8 Turbo (LMM)

    DURAMAX DIESEL 6.6L V8 Turbo (LMM) Truck Engine
    2007 Interim Model Year Summary

    • New Engine For All Applications For The 2007 Interim Model Year
    • New Fuel Injectors Improve Combustion Characteristics
    • Durability Enhancement For Variable-Geometry Turbocharger
    • Larger Exhaust Gas Recirculation Chamber
    • Closed Crankcase Ventilation System
    • Diesel Particulate Filter System
    • Intake Throttle For Precise Combustion Temperature Control
    • Electrically Variable Engine Cooling Fan
    • Increased Engine Control Processing
    • Lower Output Fleet Version Dropped


    The all-new 2007 Chevrolet Silverado and GMC Sierra 2500 HD and 3500 pickup trucks are the first applications for the new Duramax Diesel 6.6L V8 Turbo (LMM), which will be introduced in February, 2007. . In addition, the Chevrolet Express and GMC Savana full-size vans and Chevrolet Top Kick and GMC Kodiak medium-duty trucks will also be equipped with the newly engineered Duramax Diesel 6.6L V8 Turbo (LMM) beginning in January, 2007.

    Sophisticated solenoid injectors are used to precisely control combustion and to take advantage of the cleaner Ultra Low Sulfur fuel federally mandated to be available for all on-road diesel vehicles for the 2007 model year. The injectors have six specially shaped holes, developed by Powertrain engineers to better atomize fuel for complete combustion of the fuel. The injectors are programmed to inject fuel into the combustion chamber at multiple intervals during one compression stroke. By doing this, the combustion event can be tailored to lower emissions and reduce noise at its source.

    The unique variable-geometry vane-type turbocharger is housed inside the “V†of the Duramax Diesel 6.6L V8, where it is cooled by the engine’s cooling system. For 2007, the compressor is changed to a “boreless†type, which will increase durability at high rpm.

    To help control combustion temperatures, exhaust gas is introduced into the intake system. The exhaust gas is also cooled inside an chamber, which was made larger for the 2007 model year to contribute to achieving lower emissions.

    The crankcase ventilation system is a sealed chamber between both cylinder banks of the Duramax Diesel 6.6L V8 to ensure that emissions from the crankcase are kept to a minimum.

    To accomplish a dramatic reduction in emissions of particulate matter (PM), a complex ceramic-type exhaust gas filter is installed behind the oxidizing catalyst already in the exhaust system. The filter replaces the muffler in location, and consists of hundreds of small, porous tubes blocked at one end, which force the exhaust gas through the walls of the tubes, which trap PM. The trapped particles are then burned off by the heat of the exhaust, which reaches 550 degrees Celsius. Sensors detect the differential pressure between exhaust gas entering and exiting the filter, and signal the engine control module (ECM) to adjust combustion to maintain the exhaust gas temperature. The use of Ultra Low Sulfur fuel is necessary, and it will be the only diesel fuel available for on-road vehicles at the beginning of the 2007 Model Year.

    During low load conditions such as idling for extended periods and unladen low-speed driving, the temperature of the exhaust falls. To increase the amount of load on the engine during those periods, a throttle is added to the intake system, upstream of the turbocharger. This throttle is operated by the ECM as an additional control for combustion temperatures.

    The engine cooling fan is now controlled by the ECM. This allows the engine cooling system to be assisted by the fan only when necessary, which results in more precise control over the engine temperature and also aids efficiency and improves fuel economy slightly.

    The powerful E35 ECM which added more processing capacity for the 2006 Model Year is reprogrammed to include substantially more functions. Adding to the existing functions such as the variable-geometry turbocharger, the E35 ECM now controls the new injectors, the data from the diesel particulate filter pressure sensors, the new intake throttle operation, and the electrically variable engine cooling fan.

    The lower-output option for fleet versions of the engine that was introduced for the 2003 Model Year has been dropped.

    The Duramax Diesel 6.6L V8 provides class-leading output, exclusive durability enhancing features and superior noise and vibration control for GM’s heavy-duty pickups, commercial vans, and medium-duty trucks. This 90-degree turbodiesel V8 combines the best design and manufacturing elements of General Motors Powertrain worldwide. With vast experience in a wide range of climate conditions, driving cycles and ownership demands, GM Powertrain is responsible for engine control systems and electronics.

    The Duramax Diesel 6.6L V8’s compact, exceptionally rigid cast-iron engine block provides the foundation for smooth, low-noise operation. It features induction hardened cylinder bores – a technique borrowed from larger diesel engines and exclusive in the pickup class – and four-bolt, crossed-drilled bearing caps. A die-cast aluminum lower crankcase strengthens the engine block and serves as the lower engine cover, keeping weight to a minimum. The forged steel crankshaft is surface-hardened by nitriding – a process widely viewed as the most effective means of limiting wear and assuring durability. Aluminum pistons minimize reciprocating mass and improve efficiency. Each has a small hole cast in its skirt, allowing jets to spray cooling oil through a cast channel and up toward the bottom of the piston bowl, where most heat is generated.

    Aluminum cylinder heads deliver strength greater than or equal to cast iron with considerably less weight. The Duramax also has four valves per cylinder – the standard for contemporary luxury-car diesels – and an integrated oil cooler. Several features make it easier to service. Its compact size leaves more space around the engine when it’s installed in the vehicle. The timing gears are at the front of the engine for easy access, and in heavy-duty pickups, the customer can remove the fuel filter simply by leaning into the engine compartment.

    The Duramax Diesel 6.6L V8 operates on the direct injection principle which, other things equal, allows more complete combustion than the older style indirect injection and decreases specific fuel consumption as much as 20 percent. Each state-of-the-art high-pressure injector has its own solenoid to manage fuel spray, the latest injectors featuring six spray points in each injector tip for better fuel vaporization. The solenoid-type injectors reduce the amount of fuel leakage between pulses. They allow more precise fuel control, with more consistent performance under hot-fuel conditions, and greatly reduce the potential for clogging due to fuel contamination.

    The injectors are installed directly into the head and are coded so that the E35 ECM can precisely match the flow characteristics of each injector on a particular engine to compensate for small variations, ensuring exact fuel delivery. For the 2006 Model Year, a new fuel pump increased fuel pressure from 23,000 psi (roughly 300 times greater pressure than the typical gasoline injection system) to 26,000 psi, and the fuel lines and rails have been strengthened for the higher pressure. Also in 2006, the compression ratio was lowered from 17.5:1 to 16.8:1 to improve the operating smoothness of the engine.

    As continuing development aimed at lowering diesel emissions progressed, the exhaust gas recirculation (EGR) system was enlarged for the 2006 Model Year and installed in all Duramax Diesel 6.6L V8s. The EGR system recycles some exhaust gas back into the intake stream to cool combustion and reduce oxides of nitrogen (NOx) emissions. The Duramax Diesel 6.6L V8 system features a unique cooling process that increases its effectiveness. Hardware required includes: plumbing that carries some exhaust gas from the turbocharger to the intake, an EGR control valve and a stainless steel cooling element. The EGR valve is managed by the E35 ECM.

    The EGR cooling element bolts to the right side of the engine, on the inboard side of the cylinder head, with jackets fed by engine coolant. Returned exhaust gas passes through a spiraled passage in the element, and the temperature of the gas is lowered before it returns to the combustion chamber. The size and capacity of the cooling element has been increased for 2007 model year.

    The current E35 ECM was adopted for the 2006 Model Year, and to take advantage of its greater processing power, revised control strategies were installed which allow faster starting and reduced cold-cranking times.

    The Duramax Diesel 6.6L V8 was launched in the Chevrolet Silverado and GMC Sierra 2500HD and 3500 Series trucks with Allison automatic transmissions in 2001. Application expanded to the Chevrolet Kodiak and GMC Topkick medium-duty trucks for 2003, with 16,000, 18,000 and 19,500-pound gross vehicle weight ratings (GVWR). World-class diesel engines such as the Duramax Diesel 6.6L V8 share two key characteristics: incredible torque to tow or haul loads, and higher-rev horsepower for smooth, flexible over-highway travel.

    A turbocharger increases power by pumping additional compressed air into the engine’s combustion chambers, in turn allowing a greater quantity of fuel to combust at the optimal oxygen/fuel ratio. In a conventional turbo, the turbine spins as exhaust gas flows out of the engine and over the turbine’s blades, concurrently spinning a compressor wheel at the opposite end of the turbine shaft and pumping more air into the intake system. The turbine blades are fixed, and the amount of boost pressure is in a sense static, varied only by how fast the turbine spins as exhaust gas flows from the engine: The faster the engine operates, the more exhaust pressure and the higher the turbo boost pressure. Typically, maximum boost pressure is controlled by a wastegate, or a release valve that bleeds off excess pressure when boost reaches a prescribed level.

    Refinements in 2005 included an overall reduction in exhaust emissions and an increase in torque output, which was enabled by significant hardware changes in 2004. Those changes included a new variable-geometry turbocharger. Self-adjusting turbine vanes and sophisticated electronic controls automatically adjust boost pressure and exhaust backpressure. The vanes direct exhaust gas at the turbocharger’s turbine blades. These vanes can be opened and or closed to vary the amount of boost pressure. An electro-hydraulic device operated with engine oil, similar in concept to a camshaft phaser, adjusts the turbine vane angle. The variable-geometry turbo has its own sensors managed by the engine control module (ECM). A solenoid controls oil pressure against a piston that operates a small cam, which works on a unison ring that moves the turbine vanes simultaneously. As the cam turns, it varies the angle of the blades relative to the turbine wheel. The crucial advantage: With the moveable blades, boost pressure can be controlled independent of engine speed.

    The variable-geometry turbo presents a number of benefits over the conventional fixed-geometry type. Boost can be controlled more precisely, with a greater range of modulation, than with a fixed-blade turbine. The Duramax Diesel 6.6L V8’s turbo eliminates the need for a wastegate, which is often the first turbocharger component to fail as mileage accumulates. Because the variable-geometry turbo can essentially change resistance and adjust the amount of exhaust backpressure, it also eliminates a separate exhaust pressure regulator, which was previously used to manage engine or compression braking.

    Maximum boost in the Duramax Diesel 6.6L V8 remains 20 psi. Yet boost pressure can be varied more subtly over the engine’s rpm range. This presents itself to the customer as more immediate engine response, with virtually no turbo “lag.†Equally important, the ECM measures a number of parameters, from operating temperature to engine speed to fuel injection timing to load demands, when managing the turbine vanes and controlling boost, so the turbocharger operates more efficiently in all conditions. Combined with improvements to the fuel system, the variable-geometry turbocharger allows the Duramax Diesel 6.6L V8 to deliver more power with lower exhaust emissions and no decrease in overall fuel efficiency.

    Late in the 2006 Model Year, structural changes to the block and connecting rods increased the strength of the engine, which allowed calibration changes that increased output for the applications in the Chevrolet Silverado and GMC Sierra pickups to the current horsepower and torque levels (see specifications).

    The Duramax Diesel 6.6L V8 is equipped with two-piece rocker covers that accommodate external connections for the fuel lines and new fuel injectors. These resemble conventional rocker covers, but they are split lengthwise along the plane of the top surface of the cylinder head. The lower, rectangular piece of the rocker cover rings the perimeter of the cylinder head and bolts to the head like a conventional cover. The upper portion of the rocker cover attaches to the lower piece. The new two-piece rocker covers ease access to the fuel rails and injectors. Previously, the rocker covers and then the fuel lines had to be removed in order to reach the fuel injectors. The top piece of the new rocker cover is scalloped on its lower edge, around the point where the injectors fit into the cylinder heads. The injectors are now exposed on the engine, and can be removed with no other disassembly required. Such serviceability considerations are particularly significant in an engine like the Duramax Diesel 6.6L V8, with an anticipated useful life beyond 200,000 miles.

    Fast-heating glow plugs reduce pre-start heating time without increasing draw on the battery. All diesel engines are equipped with glow plugs – essentially heating elements that pre-heat the combustion chambers to sufficient temperature for compression ignition. The Duramax Diesel 6.6L V8’s glow plugs draw 6.6 watts of electricity, as before, but the element has been redesigned to more efficiently convert electricity to heat. Moreover, the glow-plug controller is specifically calibrated for the Duramax Diesel 6.6L V8’s new engine control module and allows pulse width modulation, which manages current more like a rheostat than an on-off switch.

    FSTDMAX New Member

    May 27, 2008
    Stillwater, MN
    Good read. Thanks for posting.

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