PRE-RELEASE
Engine Component Description (LAU or LBW)
| Engine Component Description (LAU or LBW) |
The High Feature V6 VIN Code 4 RPO LAU is a 2.8L turbocharged engine incorporating two intake and two exhaust valves per cylinder. Individual intake and exhaust camshafts (DOHC) with camshaft position actuators are mounted on each cylinder head. The cylinders are arranged in two banks of three with a 60 degree included angle. The right bank of cylinders are number 1-3-5 and the left bank of cylinders are 2-4-6, viewed from the flywheel end of the engine. The engine firing order is 1-2-3-4-5-6.
| Crankcase |
The cylinder block is constructed of aluminum alloy by precision sand-casting with cast in place iron cylinder liners. Each steel main bearing cap incorporates six bolts bolting the cap into the engine block. Along with two outer and two inner bolts, two side bolts are used in the deep skirt block. To prevent aeration, oil return from the valvetrain and cylinder heads is channeled away from the rotating and reciprocating components through oil drain back passages incorporated into the cylinder heads and engine block. Pressure-actuated piston oil cooling jets are mounted between opposing cylinders. A knock sensor is located on each side of the exterior of the engine block. The crankshaft position sensor is located on the right side of the exterior of the engine block.
| Crankshaft |
The crankshaft is a hardened, forged steel design with 4 main bearings. Crankshaft thrust is controlled by the upper part of main bearing number 3. The crankshaft has a reluctor wheel for position sensing pressed onto the rear part of the crankshaft, in front of the main bearing. A micro encapsulated adhesive is used on the reluctor wheel to aid retention. The crankshaft is internally balanced, and has an integral oil pump drive machined into the nose in front of the front main journal.
| Connecting Rods and Pistons |
The connecting rods are steel and have full floating piston pins. The piston pins are a slip fit in the bronze bushed connecting rod. Round wire retainers are used to retain the piston pin into the piston. The cast aluminum pistons incorporate a polymer-coated skirt to reduce friction. The piston uses two low tension compression rings and one multi-piece oil control ring.
| Camshaft System |
The camshaft drive system consists of one primary timing drive chain driven by the crankshaft sprocket. The primary timing drive chain drives two intermediate drive shaft sprockets. Each oil pressure fed intermediate drive shaft sprocket drives separate secondary timing drive chains. Each secondary timing drive chain drives the respective cylinder head's intake and exhaust camshaft position actuators.
The primary timing drive chain uses two stationary timing drive chain guides and a hydraulically-actuated tensioner with built-in shoe. The tensioner minimizes timing drive chain noise and provides accurate valve action by keeping slack out of the timing drive chains and continuously adjusting for timing drive chain wear. The tensioner incorporates a plunger that adjusts out with wear allowing only a minimal amount of backlash. The tensioner is equipped with an oiling jet to spray oil onto the timing components during engine operation.
The secondary timing drive chains use a stationary timing drive chain guide and movable timing drive chain shoe. The secondary timing drive chain shoe is under tension from a hydraulically-actuated tensioner. All tensioners are sealed to the head or block using a rubber coated steel gasket. The gasket traps an adequate oil reserve to ensure quiet start-up.
| Camshaft Position Actuator System |
The engine incorporates a camshaft position actuator for each intake and exhaust camshaft. Camshaft phasing changes the inlet and exhaust valve timing as engine operating conditions vary. Dual camshaft phasing allows the further optimization of performance, fuel economy and emissions without compromising overall engine response and driveability. Variable valve timing also contributes to a reduction in exhaust emissions. It optimizes exhaust and inlet valve overlap.
The camshaft position actuator is a hydraulic vane-type actuator that changes the camshaft lobe timing relative to the camshaft drive sprocket. Engine oil is directed by a camshaft position actuator oil control valve to the appropriate passages in the camshaft position actuator. Oil acting on the vane in the camshaft position actuator rotates the camshaft relative to the sprocket. At idle, both camshafts are at the default or "home" position. At this position, the exhaust camshaft is fully advanced and the intake is fully retarded to minimize valve overlap for smooth idle. An internal lock pin locks the inner rotor to the outer camshaft position actuator housing at idle and maintains this position during start-up conditions. Under other engine operating conditions, the camshaft position actuator is controlled by the engine control module (ECM) to deliver optimal intake and exhaust valve timing for performance, driveability and fuel economy. The camshaft position actuator incorporates an integral trigger wheel, which is sensed by the camshaft position sensor mounted in the front cover to accurately determine the position of each camshaft. Each camshaft position actuator has a specific timing drive mark for right or left bank application, as the camshaft position actuators are common bank to bank. The exhaust camshaft position actuator has a different internal configuration than the intake camshaft position actuator since the exhaust camshaft position actuator phases in the opposite direction relative to the inlet camshaft position actuator.
The camshaft position actuator oil control valve (OCV) directs oil from the oil feed in the head to the appropriate camshaft position actuator oil passages. There is one OCV for each camshaft position actuator. The OCV is sealed and mounted to the front cover. The ported end of the OCV is inserted into the cylinder head with a sliding fit. A filter screen protects each OCV oil port from any contamination in the oil supply.
The camshaft front journal has several drilled oil holes to allow camshaft position actuator control oil to transfer from the cylinder head to the camshaft position actuator. The center camshaft bolt hole is counterbored to allow oil to flow around the camshaft bolt and to the camshaft position actuator. Oil in this oil passage is used to move the camshaft position actuator to the default or home position. Radially outward from the center of the journal is a set of four drilled camshaft position actuator oil holes. Oil in this group of oil holes is used to move the camshaft from the default position to a specific set position as determined by the ECM. Seal rings are used at the front and rear of the front camshaft journal to prevent oil leakage from the camshaft position actuator hydraulic system. The seal is made from a plastic compound that resists wear and has a diagonal end gap to enhance sealing. The camshaft position actuator is mounted to the front end of the camshaft and the timing notch in the nose of the camshaft aligns with the dowel pin in the camshaft position actuator to ensure proper cam timing and camshaft position actuator oil hole alignment.
| Cylinder Head Assembly |
The cylinder heads are cast aluminium. The valve seat inserts and valve guides are sintered. Each cylinder has two intake valves and two exhaust valves. These are actuated by roller lifters mounted on bearings in a hydraulic valve clearance adjustment device (SHLA). Separate exhaust and intake camshafts are supported by bearings machined into the cylinder head. The front camshaft bearing cap is used as a thrust control surface for each camshaft. In addition to the thrust bearing surfaces in the front camshaft bearing caps, there is a plastic thrust washer installed between the camshaft position actuator and the forward face of the cylinder head/camshaft thrust cap to supplement camshaft thrust control. Each spark plug is shielded by a tube that is pressed into the cylinder head. Each spark plug ignition coil is also mounted through the spark plug tube. The engine coolant temperature (ECT) sensor is threaded into the left cylinder head.
| Induction System |
The intake manifold consists of two cast aluminum components. Two short bolts in the lower intake manifold and four long bolts, that pass through both manifolds, mount the intake manifold assembly to the cylinder heads. Additionally two bolts mount the upper intake manifold to the lower intake manifold. The throttle body, manifold absolute pressure (MAP) sensor, Evaporative Emissions (EVAP) solenoid and tubes, Positive Crankcase Ventilation (PCV) tubes, fuel rail support bracket, fuel injector wiring harness bracket, and brake booster hose are mounted to the upper intake manifold. The fuel injector wiring harness, fuel rail assembly, and fuel injectors are mounted to the lower intake manifold. An electronically controlled throttle (ETC), through the ECM, coordinates the input from the driver with various control components.
| Right and Left Bank Designation |
Right hand (RH) and left hand (LH) designation through the engine mechanical section are viewed from the rear of the engine or from inside.
| Turbocharger |
The turbocharger is a compressor used for forced induction of the engine, compressing the intake air so as to "pack" the cylinder with air/fuel. The turbocharger consists of a turbine wheel in the exhaust stream and a compressor wheel in the intake stream, mounted on a common shaft. The exhaust gases drive the turbine wheel, which drives the compressor wheel in the intake stream, thereby compressing the intake gases. This increases the density of the air/fuel mixture entering the cylinders above what can be achieved with normal aspiration. The speed, and therefore output pressure, of the turbocharger is controlled by the wastegate. The wastegate is a variable bypass that allows some of the exhaust gasses around the turbine wheel and directly into the exhaust system. This is how the turbocharger boost pressure, and the turbocharger operating speed, is controlled, as the boost pressure is directly related to the speed of the compressor wheel. The wastegate is controlled by the ECM and operates via a vacuum solenoid. The turbocharger is also both oil- and water-cooled via the engine lubrication and cooling systems, respectively.
| Oil Cooler |
The oil cooler lowers the engine temperature by cooling the oil with the engine coolant. Engine coolant is directed from the water pump to the oil cooler by a coolant tube. The oil cooler attaches directly to the oil filter housing.
