GENERAL DESCRIPTION AND SYSTEM OPERATION
Cylinder Head and Gasket
The cylinder head is made of an aluminum alloy. The
cylinder head uses crossflow intake and exhaust ports.
A spark plug is located on the exhaust side of each combustion chamber.
Crankahaft
The crankshaft is supported by the five main bearings.
The number three bearing is the end thrust bearing. The
main bearings are lubricated from the oil holes which intersect
the main oil gallery on the exhaust side of the engine
block.
Timing Belt
The timing belt coordinates the crankshaft and the camshaft
and keeps them synchronized. The timing belt also
turns the coolant pump. The timing belt and the pulleys
are toothed so that there is no slippage between them.
There is a tension pulley that maintains the correct timing
belt tension. The timing belt is made of a tough reinforced
rubber similar to that used on the serpentine
accessory drive belt. The timing belt requires no lubrication.
Oil Pump
The oil pump draws engine oil from the oil pan and feeds
it under pressure to the various parts of the engine. An
oil strainer is mounted before the inlet of the oil pump to
remove impurities which could clog or damage the oil
pump or the other engine components. When the drive
gear rotates, the driven gear rotates. This causes the
space between the gears to open and narrow constantly,
pulling oil in from the oil pan when the space opens
and pumping the oil out to the engine as it narrows.
At high engine speeds, the oil pump supplies a much
higher amount of oil than required for lubrication of the
engine. The oil pressure regulator prevents too much oil
from entering the engine lubrication passages. During
normal oil supply, a coil spring and a valve keep the bypass
closed, directing all of the oil pumped to the engine.
When the amount of oil being pumped increases, the
pressure becomes high enough to overcome the force
of the spring. This opens the valve of the oil pressure
regulator, allowing the excess oil to flow through the
valve and drain back to the oil pan.
Oil Pan
The oil pan is mounted to the bottom of the cylinder
block. The oil pan houses the crankcase and is made of aluminum.
Engine oil is pumped from the oil pan by the oil pump.
After the oil passes through the oil filter, the oil is fed
through two paths to lubricate the cylinder block and the
cylinder head. In one path, the oil is pumped through the
oil passages in the crankshaft to the connecting rods,
then to the pistons and the cylinders in the cylinder
block. The oil then drains back into the oil pan. In the
second path, the oil is pumped through the oil passages
to the camshaft. The oil passes through the internal passageways
in the camshafts to lubricate the valve assemblies
in the cylinder head before draining back into
the oil pan.
Exhaust Manifold
A single four-port, rear-takedown exhaust manifold is
used with this engine. The exhaust manifold is designed
to direct the escaping exhaust gases out of the combustion
chambers with a minimum of backpressure.
Intake Manifold
The intake manifold is made of aluminum. The intake
manifold is heated by the engine coolant. An air/fuel
mixture is transferred through the intake manifold to the
engine cylinders for combustion.
Camshaft
The cast-iron camsahaft is supported by the five bearing surfaces in an aluminum camshaft carrier located on th top of the cylinder head.
The camshaft gear is power driven by the crankshaft, using the timing belt.
Exhaust Gas Recirculation Valve
The exhaust gas recirculation (EGR) system is used to
lower oxides of nitrogen (NOX) emission levels caused
by high combustion temperatures. The main element of
the system is the EGR valve which is operated electrically by the ECM.
The EGR valve feeds small amounts of exhaust gas into
the intake manifold to decrease the combustion temperature.
The amount of exhaust gas recirculated is controlled
by variations in electrical signal and exhaust back
pressure. If too much exhaust gas enters, combustion
will not take place. For this reason, very little exhaust
gas is allowed to pass through the valve, especially at
idle.
The EGR valve is controlled precisely by ECM according to various operating condition of the engine.
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