GM 3.6 Liter V6 LFX Engine

The 3.6 liter V6 LFX engine is GM’s new high-feature V6 engine, replacing the 3.6L direct-injected six-cylinder engine (code LLT). Compared to the LLT it replaces, the LFX is lighter and more powerful, and also features the following features:

• New cylinder head design with integrated exhaust manifold
• Improved intake port design and larger intake valves within the cylinder heads
• Longer-duration intake camshafts
• Composite intake manifold
• New fuel pump and isolated fuel rail
• New, optimized-flow fuel injectors
• Structural front cover and cylinder block enhancements
• Stronger and lighter-weight connecting rods
• Camshaft cap and throttle body design enhancements
• E85 ethanol capability

The engine further refines an already well-balanced powerplant. It now uses new, lighter-weight components and enhancements designed to improve performance, efficiency, and durability.

Engine highlights include:

• Aluminum Engine Block & Integral Oil Pan: the 3.6L V6 VVT’s engine block is cast from A319 aluminum alloy. This aluminum-intensive construction means less weight and greater efficiency than conventional cast-iron engines – and less weight translates to improved vehicle fuel economy. The sand-mold-cast block features strong cast-in iron bore liners, six-bolt main caps, and inter-bay breather vents. A cast aluminum oil pan is stiffened to improve powertrain rigidity and reduce vehicle vibration.
• Rotating Assembly with Oil-Spray Cooled Pistons: the crankshaft is manufactured from forged steel, while the connecting rods are made of powdered metal that features a higher ratio of copper, which makes them stronger and enables them to be lighter.
  The V6 VVT engine family was developed with pressure-actuated oil squirters in all applications. The jets reduce piston temperature, which in turn allows the engine to produce more power without reducing long-term durability.
• Integrated Cylinder Heads/Exhaust Manifolds: the LFX’s new cylinder head design has a revised intake port design that enhances airflow to the combustion chambers. Larger-diameter intake valves are used in the heads and work in conjunction with new, longer-duration intake camshafts to provide the engine’s boost in horsepower. By using larger valves and holding them open longer, more of the air is pulled into the combustion chamber, for a more powerful combustion. The exhaust manifold is incorporated with the cylinder head, which saves weight, reduces complexity and helps promote a quicker light off of the catalytic converter, which further helps reduce emissions.
• Direct Injection: direct injection moves the point where fuel feeds into an engine closer to the point where it ignites, enabling greater combustion efficiency. It fosters a more complete burn of the fuel in the air-fuel mixture, and it operates at a lower temperature than conventional port injection. That allows the mixture to be leaner (less fuel and more air), so less fuel is required to produce the equivalent horsepower of a conventional, port injection fuel system. Direct injection also delivers reduced emissions, particularly cold-start emissions, which are cut by about 25 percent.
• E85 Flex-Fuel Capability: E85 is a clean-burning, domestically produced alternative fuel composed of 85 percent ethanol alcohol and 15 percent gasoline. Ethanol is renewable and produces fewer greenhouse gas emissions in the combustion process. It can be produced from various feed stocks, including corn and wheat stalks, forestry and agricultural waste and even municipal waste.
• Dual Overhead Cams with Four Valves per Cylinder & Silent Cam Drive: four-valves-per-cylinder with inverted-tooth chain cam drive contributes to the smoothness and high output of the LFX. The engine incorporates a timing chain with an inverted tooth design. These smaller links engage at a lower impact speed, which decreases the noise generated. In conjunction with the smaller pitch chain, the number of teeth on the sprockets are increased, which increases the meshing frequency and further reduces noise and vibration.
  Four valves per cylinder and a silent chain valvetrain contribute to both smoothness and high output. Four-cam phasing changes the timing of valve operation as operating conditions such as rpm and engine load vary.
• Variable Valve Timing: variable valve timing (VVT), or cam phasing, helps the LFX deliver optimal performance and efficiency, and reduced emissions. It allows linear delivery of torque, with near-peak levels over a broad rpm range, and high specific output (horsepower per liter of displacement) without sacrificing overall engine response, or driveability. The system changes valve timing on the fly, maximizing engine performance for a variety of operating conditions. At idle, for example, the cam is at the full advanced position, enabling exceptionally smooth idle quality. Under other operating demands, cam phasing adjusts to deliver optimal valve timing for performance, driveability and fuel economy. At high rpm it might retard timing to maximize airflow through the engine and increase horsepower. At low rpm it can advance timing to increase torque. Under light-load driving it can retard timing at all engine speeds to improve fuel economy.
• Composite Intake Manifold and Fully Isolated Composite Camshaft Covers: the upper intake manifold for the LFX is made from composite material and provides mass savings over an aluminum manifold, with a carefully designed structure that helps ensure quiet engine operation. The surfaces on the cam covers are shaped to limit the broadcasting of undesirable noise, and the covers use isolating perimeter gaskets, as well as isolating radial lips around the tubes that accommodate the spark plugs. These effectively de-couple the covers from vibration generated in the block and engine during combustion. Acoustic dampening has also been added for additional NVH improvements.
• Refinement, Durability and Maintenance: additional changes incorporated in the LFX deliver greater refinement, quietness and durability, starting with revisions to the front cover. It was redesigned with additional support ribs on the backside and an additional fastener to improve noise and vibration characteristics. The cylinder block is modified slightly to accommodate the front cover’s additional fastener. In addition, the camshafts feature new saddle-type caps for improved durability. Finally, the throttle body is updated with a new, digital throttle position feature that eliminates a previous mechanical contact for more trouble-free operation.