General description and operation of the engine (Chevrolet Captiva 1)

Cylinder head and gasket

The cylinder head is made of aluminum alloy. The cylinder head has intake and exhaust channels on different sides. The spark plug is located in the center of each combustion chamber. The cylinder head contains double camshafts.

Crankshaft

The crankshaft has counterweights built into it, cast together for balancing. Oil holes run through the center of the crankshaft and supply oil to the connecting rods, bearings, pistons and other parts. The axial load is supported by thrust washers mounted on the central journal.

Gas distribution mechanism drive belt

The drive belt of the gas distribution mechanism coordinates the rotation of the crankshaft and the double crankshafts of the upper arrangement and synchronizes them. The drive belt of the gas distribution mechanism also rotates the coolant pump. The timing belt of the gas distribution mechanism and the pulleys have teeth, so that no slippage is allowed between them. There are two idle pulleys. The automatic tensioner ensures that the drive belt of the gas distribution mechanism is properly tensioned. The drive belt of the gas distribution mechanism is made of strong reinforced rubber, similar to the rubber used for the bending drive belt. The drive belt of the gas distribution mechanism does not require lubrication.

Oil pump

The oil pump draws engine oil from the oil pan and delivers it under pressure to various parts of the engine. An oil filter is installed before the inlet to the oil pump to remove contaminants that could clog or damage the oil pump or other engine components. As the crankshaft rotates, the driven gear of the oil pump rotates. This causes the gap between the gears to constantly narrow and open, sucking oil from the oil pan when the gap opens and pumping oil into the engine when it narrows.

At high engine speeds, the oil pump delivers much more oil than is needed to lubricate the engine. The oil pressure regulator prevents excess oil from entering the engine's oil passages. When the oil supply is normal, the spool spring and valve hold the bypass closed, directing all the oil into the engine. As the volume of oil being pumped increases, the pressure increases to a level sufficient to overcome the spring force. This opens the oil pressure regulating valve, allowing oil to flow through the valve and drain back into the oil pan.

Oil pan

The oil pan is installed below the cylinder block. The oil pan contains the crankcase, the oil pan is made of aluminum alloy.

Engine oil is pumped from the oil pan by the oil pump. After passing through the oil filter, it is sent through two paths to lubricate the cylinder block and cylinder head. In one path, the oil is pumped through oil passages in the crankshaft to the connecting rods and then to the pistons and cylinders. It then drains back into the oil pan. In the second path, the oil is pumped through oil passages to the crankshaft. The oil passes through internal passages in the camshafts to lubricate the valve bodies before draining back into the oil pan.

Exhaust manifold

This engine uses a single, four-port, rear-exhaust manifold. The manifold is designed to discharge exhaust gases directly from the combustion chamber with minimal back pressure. The oxygen sensor is mounted on the exhaust manifold.

Intake manifold

The intake manifold has four independent ports and uses dynamic boost to increase torque at low and medium speeds.

Camshafts

DOHC engine (two overhead camshafts), which means there are two camshafts. One camshaft controls the intake valves, the other camshaft controls the exhaust valves. The camshafts are mounted on journals on top of the engine (in the cylinder head) and are held in place by the camshaft heads. The camshaft journals of the cylinder head are drilled to create oil passages. Engine oil is forced under pressure to the camshafts where it lubricates each camshaft journal. The oil returns to the oil pan through drain holes in the cylinder head. The camshaft lobes are combined into a single camshaft to open and close the intake and exhaust valves to deliver the correct amount of oil at the correct time. The camshaft lobes are washed by pressurized oil sprays from the camshaft journals.

Exhaust Gas Recirculation (EGR) Valve

The exhaust gas recirculation (EGR) system is used to reduce the nitrogen oxide (NOX) content of the exhaust gases produced by high combustion temperatures. The main component of this system is the EGR valve, which is controlled by an electrical circuit.

The exhaust gas recirculation valve recirculates a small amount of exhaust gas into the intake manifold to reduce combustion temperatures. The amount of recirculated gas is controlled by the engine control module (ECM) in response to changes in engine load. If too much exhaust gas is introduced, combustion does not occur. For this reason, only a small amount of exhaust gas is allowed to pass through this valve, especially at idle.



The exhaust gas recirculation valve is normally open in the following cases:

• Warming up the engine
• Above idle speed

(The article is based on data from the website «ChevyMan»)