Engine Description

WARNING: This page is about a different variant/trim than selected.

Active Thermal Management

A new cooling system called active thermal management helps the engine warm up and achieve its optimal engine temperature more quickly. The system eliminates the need for a conventional thermostat. A rotary valve system is used to distribute coolant through the engine in a targeted manner.

Balance Shaft Assembly

A balance shaft assembly is attached to the engine block lower structural extension. The balance shafts are driven by the balance chain located in the rear of the engine. Chain tension is monitored by a hydraulic tensioner that is supplied pressure by the engine oil pump.

Camshaft Carrier

The intake and exhaust camshafts mount to the lower section of the camshaft carrier. The upper section includes the ignition coils, the high pressure fuel pump, the four intake camshaft profile actuators, and the two exhaust camshaft profile actuators for the sliding cam valve lift system.

Camshaft Drive

A roller chain is used for camshaft drive. There is a tensioner and active guide used on the slack side of the chain to control chain motion and noise. The chain drive promotes long valve train life and low maintenance.

Camshaft Profile Actuators

The intake and exhaust camshaft profile actuators are electromagnetic actuators. They are used to axially move the lobe packs in conjunction with the shifting groove. Intake and exhaust camshaft profile actuators are different. The exhaust actuator pins are 4 millimeters while the intake actuator pins are 5 millimeters.

Coolant Control Valve

The coolant control valve includes the main rotary valve and the block rotary valve. The main rotary valve distributes coolant to the transmission and engine oil heat exchangers, as well as the radiator and the cabin heat exchangers. An integrated exhaust manifold exchanger, actually an additional port on the main rotary valve, uses heat from the exhaust to heat the coolant. The heated coolant can then be used in the cabin heat exchanger, as well as by the engine and transmission oil heat exchangers, to warm the engine and transmission oils. The coolant control valve is controlled by the ECM.

Crankshaft

The crankshaft in the 2.7-liter L3B in-line four-cylinder engine is made of forged micro alloy steel. Four counterweights are scalloped for mass reduction and topped for precise engine balance. A harmonic balancer is used to control torsional vibration.

Crankcase Ventilation System

The crankcase ventilation system incorporates a pre-separator. It's located in the left side of the engine block, below the coolant control valve, and behind the PCV baffle cover. As crankcase gases enter the pre-separator, oil separation occurs and the separated oil drains back to the oil pan through two oil drain channels in the block. The blowby flows internal from the pre-separator through the block and head into the fine separator.

Cylinder Head

The cast aluminum alloy cylinder head features a dual overhead camshaft design. The combustion chamber is designed for increased swirl efficiency to maximize combustion. The fuel injectors are located under the intake ports. The exhaust manifold is integrated into the cylinder head.

Electric Water Pump

Mounted to the bottom right side of the engine, an electric water pump eliminates the parasitic drag that comes with a conventional engine-driven water pump. It incorporates a three-phase motor and pump impeller to distribute coolant through the entire cooing system. The ECM controls the water pump over the LIN network.

Engine Block

The cast aluminum alloy cylinder block features four cast-in-place iron cylinder liners and five crankshaft bearings. The thrust bearing is located on the second bearing from the rear of the engine.

Engine Block Lower Structural Extension

In the engine block structural extension is the oil pump and the balance shafts installed.

The balance shafts are driven by the balance chain. The chain is tensioned by a hydraulic tensioner that is supplied pressure by the engine oil pump. This design promotes the maximum effectiveness of the balance shaft system and reduces noise and vibration.

The oil pump assembly is fastened directly to the rear of the balancer shaft assembly and by the oil pump drive shaft. The oil pump assembly possesses variable flow capability which is made possible by a shift of the circular vane arrangement and the actuation of an oil control valve assembly guided by the ECM. The variable flow capability of the pump optimizes oil flow to the engine components when needed. During performance maneuvers and acceleration the oil pump operates in a steady high pressure state. However, during steady low load touring speeds on level terrain the oil pump operates in a steady low pressure state.

Fine Separator Assembly

In the fine separator assembly, the blowby flows through a fine oil separator and the pressure regulation valve. The fine oil separator has an internal oil drain with a check valve. After the blowby has passed the pressure regulation valve, it can flow through the primary or secondary check valve.

Fuel Injection System

The engine is equipped with a central direct injection system. The fuel system consists of 4 separate direct injection fuel injectors, one high pressure fuel rail, and a high pressure fuel feed pipe that connects the high pressure fuel pump to the fuel rail. The injectors are each seated into their individual bores in the cylinder head with two combustion seals to provide sealing. The high pressure fuel pump mounts to the rear of the cylinder head and is driven by the intake camshaft. Motion is transmitted to the pump from a tri-lobe on the rear of the camshaft through a hydraulic roller lifter. Due to the location of the central direct injection system injector location this provides an increase in fuel economy and performance.

Hall Effect Sensors

Hall effect sensors are used to detect and confirm the sliding lobe position. These sensors are integrated in to the cam carrier in addition to the intake and exhaust camshaft profile actuators and provide feedback to the ECM.

Intake and Exhaust Camshafts

The engine also has an innovative Sliding Cam Valve Lift System (SCS) that modifies camshaft timing under changing engine demand. The Sliding Cam Valve Lift System (SCS) has three distinct operating modes. The SCS system enables the ECM to change the camshaft lift profile of the intake and exhaust camshafts while the engine is running. The SCS has four intake camshaft profile actuators and two exhaust camshaft profile actuators that vary the camshaft lift profile sleeve position axially on the camshaft in response to commands from the ECM.

The SCS system has three unique-sized cam lobes on each camshaft profile slider.

Power Profile: High Lift - Full capacity, conventional lift and duration. In this profile, all four cylinders are active and all valves open to their maximum lift for when the full capability of the engine is needed.
Economizer Profile: Low Lift - Reduced capacity (3 mm lift) changes the duration of the valve opening and closes the valve early. In this profile, all four cylinders are still active, but all intake valves open to a lower lift height to help save fuel under medium load conditions, such as highway driving.
Ultimate Fuel Economy Profile: AFM - Cylinder deactivation, used for increased fuel economy in light load conditions, such as highway cruising. In Active Fuel Management (AFM) mode, cylinders 2 and 3 are deactivated.

Sliding Cam Valve Lift System

The sliding cam valve lift system on the CSS engines is the first to incorporate variable lift, duration, and active fuel management. This system optimizes performance and efficiency across the RPM band. It's a key reason the engine's peak torque is available at only 1, 500 RPM.

Intake Manifold

The intake manifold is the air flow passage to the cylinder combustion chamber through the throttle body and has an effect on engine torque, power, noise, drivability, emission, fuel economy and performance. It is made of composite plastic.

Lower Oil Pan

The oil pan is made of synthetic material. The oil pan is attached at the engine block lower structural extension. The oil pans incorporates 4 jack screws that need to be used during the removal procedure.

Piston and Connecting Rod Assembly

The pistons are cast aluminum with low friction, lightweight design with two compression rings, one oil control ring assembly, and full-floating piston pins. The connecting rods are fractured at the journal and then machined for precise clearance. All pistons feature a graphite-coated skirt.

Turbocharger

The turbocharger is the device that supplies hot, compressed air, that is from the turbine/impeller created from the passing exhaust gas or ram air, to the engine to increase the power. Quick compressed air from this turbocharger expands with high temperature and causes decreasing of charging efficiency into the cylinder because density of oxygen gets lower. However charging efficiency into the cylinder increases as compressed hot air is cooled and density of air gets higher through the charge air cooler. It brings also higher fuel efficiency as well as lower CO2 emissions. Charge air cooler which is installed on top of radiator in front of car makes compressed hot air cool by airflow through the radiator grill. With the variable turbine geometry turbocharger the boost pressure is optimized in all engine conditions.

Valves

There are 2 intake and 2 exhaust valves per cylinder. Positive valve stem seals are used on all valves.

Hydraulic Valve Lash Adjuster

The valve train uses a roller finger follower acted on by a hydraulic lash adjuster. The roller finger follower reduces friction and noise.