GM 2.5 Liter I4 LKW Engine

The Ecotec 2.5L I4 (LKW) iVLC DOHC four-cylinder engine with direct injection employs variable valve lift control and start/stop technology. The variable intake valve actuation enhances efficiency and helps lower emissions, while also enhancing low-rpm torque, for a greater feeling of power at lower speeds. New start/stop technology shuts down the 2.5L engine to save fuel when the vehicle stops momentarily, such as stoplights, to save fuel and reduce emissions. The engine automatically starts again when the driver takes his or her foot off the brake. An auxiliary battery powers electric accessories such as the climate system, power windows and radio during engine restarts.

The new 2.5L is SAE-certified at 196 horsepower (145 kW) and 186 lb.-ft. of torque (253 Nm) and is offered exclusively in the Chevrolet Impala and Malibu.

Engine highlights:

• Engine Block
  : a cast aluminum cylinder block with cast-in iron liners serves as the foundation for the 2.5L. The block features cast iron bearing cap inserts and a strong, forged steel crankshaft to help reduce noise and vibrations and improve durability, while refinements to the oil distribution system enable improved flow through the engine.

  Aluminum Pistons with Jet-Spray Cooling

  : the Ecotec 2.5L uses lightweight aluminum pistons, for less reciprocating mass inside the engine to enhance efficiency, decrease vibration and bolster the feeling of performance as rpm increases. Each piston has its own directed jet that sprays oil toward its skirt, coating its underside and the cylinder wall with an additional layer of lubricant. The extra lubrication cools the pistons, reducing friction and operational noise, while also bolstering the engine’s durability.

  Cylinder Head

  : the Ecotec 2.5L has a 356T6 aluminum cylinder head cast with advanced semi-permanent mold technology to provide excellent strength, reduced machining and optimal port flow. The cylinder head is designed specifically for direct injection into each combustion chamber and includes a premium valve seat, valve guide and valve materials. The cylinder head also has integral cast oil passages that feed a set of internal oil control valves that activate cam phasers, enabling variable valve timing.

  DOHC with Enhanced Authority Cam Phasing

  : overhead camshafts are the most direct, efficient means of operating the valves, while phasing changes the timing of valve operation for an optimal balance of performance and efficiency. The 2.5L’s enhanced authority cam phasing takes the continuously variable performance to the next level, with 4X timing reluctors and digital sensors that enable more accurate timing measurements and more immediate adjustments.

  Variable Intake Valve System

  : the LKW 2.5L features a unique two-step intake valve actuation system designed to enhance efficiency and help lower emissions, while also enhancing low-rpm torque, for a greater feeling of power at lower speeds.

  When the 2.5L’s iVLC system operates in low-lift mode, the engine pumps only the air it needs to meet the driver’s demand. The system switches to high-lift mode at higher speeds or under heavy loads, providing the full output capability of the engine.

  Direct Injection

  : direct injection moves the point where fuel feeds into an engine closer to the point where it ignites, enabling greater combustion efficiency. Direct injection also reduces cold-start emissions.

  With direct injection, the higher compression ratio is possible because of a cooling effect as the injected fuel vaporizes in the combustion chamber. This reduces the charge temperature and lessens the likelihood of spark knock. The direct injection fuel injectors have been developed to withstand the greater heat and pressure inside the combustion chamber and also feature multiple outlets for best injection control.

  Cam-Driven High-Pressure Fuel Pump

  : a high-pressure, cam-driven pump provides the fuel pressure required of the direct injection system in the Ecotec 2.5L. The engine-mounted fuel pump is augmented by a conventional electrically operated supply pump in the fuel tank.

  Two-Stage, Variable-Displacement Oil Pump

  : the variable-flow oiling system helps maximize fuel efficiency. Rather than the linear operation of a conventional fixed-flow pump, a crankshaft-driven oil pump matches the oil supply to the engine load. The engine’s variable-flow pump changes its capacity based on the engine’s demand for oil.

  The flow volume of the oil pump is designed to support the engine’s oiling requirements, including piston cooling and camshaft phasing. The cam phasers are supplied with oil through separate bores in the cylinder block and head. The recirculation of the increased amount of oil in the cylinder head is permitted through additional pre-cast oil return channels.

  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, biodegradable and produces fewer greenhouse gases 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.

  Refinement Features

  : the 2.5L has refined many components to provide a quiet, efficient engine. The engine’s noise frequency signature pushes radiated noises into a higher frequency range to maintain low noise levels. Other highlights include:

  Balance shafts reduce noise through a shorter, quieter drive chain, as well as precision shaft-to-shaft reversing gears and light drag torque from driving the oil pump. The oil pump is located within the oil pan where it is driven by the second balance shift, reducing noise and providing a small drag torque for quiet balance shaft gear operation The camshaft drive uses an inverted-tooth chain to reduce noise and enhance durability.

  A unique, two-piece oil pan made of aluminum and stamped steel offers a stiff structure and noise reduction Structural camshaft and front covers improve stiffness for less noise and excellent oil sealing An acoustic intake manifold cover, a forged steel crankshaft, an isolated fuel rail and iron main bear cap inserts all help reduce noise.