computational fluid dynamics (CFD) analysis software features a higher compression ratio which helps improve fuel efficiency and has improved knock resistance. The engine features dual overhead camshafts with continuously variable valve timing and increased-authority cam phasing (increased phase rotation angle), a high-pressure returnless direct-injection fuel system with camshaft-driven fuel pump delivering at idle and at full load, higher-flowing intake and exhaust ports in the cylinder head, electronic throttle control and pistons with jet-spray oil cooling. The engine redline is 7000 rpm. The balance shafts are relocated from the cylinder block to oil pan module. The two-piece steel-aluminum oil pan features in-pan integrated oil-pump assembly driven by the balance shaft with a shorter inverted-tooth chain. Other improvements include inverted-tooth chain driving the camshaft, forged steel crankshaft, cast aluminum bedplate with main bearing cap inserts made of iron, high-pressure fuel rail with rubber-isolated assembly, acoustically shielded plastic cover for the intake manifold, and structurally enhanced aluminum camshaft cover and front cover. These improvements helped reduce noise intensity by 40% compared to the 2.4 L engine and change the noise signature into a higher frequency above 2,000 Hz. The engine also uses a variable-displacement oil pump and an actively controlled thermostat. Direct injection reduces emissions by 25%, while continuous cam phasing eliminates the need for an EGR system. Maximum engine speed is listed at 7000 rpm. Displacement for the 2.5 L engine is 2,457 cc with an bore and stroke. Compression ratio is 11.3:1. LKW Same as the LCV but features Intake Valve Lift Control (IVLC) system provides two-stage variable valve lift in addition to continuous variable timing. Continuously commanded by engine control unit, the valve rocker arm switches between high-lift and low-lift profiles on the camshaft, actuated by an oil control valve through a two-feed stationary hydraulic lash adjuster, allowing for either 4.0 or 10.5 mm lift. It also features a start-stop system. Maximum engine speed is listed at 7000 rpm. HCCI At Tech Show Torino 2008, GM Powertrain Europe announced the ignition-less HCCI (Homogeneous Charge Compression Ignition) mode of the direct injection version of 2.2 L engine. HCCI version is equipped with two-step adjustable valve lift with variable cam phasing and advanced ECU with cylinder pressure sensors, uses lean burn cycle similar to that of a diesel engine, and is claimed to further reduce fuel consumption by 15%. See also Family 0 engine Family 1 engine List of GM engines References