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CHAPTER 1ENGINE SYSTEM
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OBJECTIVESExplain the principles of internal combustion
engine operation
Identify internal combustion engine parts
Describe the function of engine parts
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Engine characteristics
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ENGINE DESIGN AND OPERATION
Four Stroke Cycle
Intake
Compression
Power
Exhaust
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TWO-STROKE CYCLE
Common in some smallengine such as lawn moverengines, and some dieselengine
Valve train is eliminated
Each upward piston stroke is
a compression stroke, andeach downward piston strokeis a power stroke in a two-stroke cycle engine.
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OTTO CYCLE
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DIESEL CYCLE
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VALVE MECHANISM AND CAM SHAFT
DRIVES
Valve mechanisms vary depending on the
camshaft location
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CAMSHAFT AND VALVE OPERATION
Intake stroke: The crankshaft completed one-
half a revolution, while the camshaft rotated one-
quarter revolution.
Compression stroke: valves remain closed. the
crankshaft rotates for one half revolution while
the camshaft turns one-quarter revolution.
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..
Power stroke: Both valves remain closed the
crankshaft turns half revolution, and the
camshaft rotates one quarter revolution.
Exhaust stroke: The crankshaft completes
another half turn, and the camshaft rotates one-
quarter revolution.
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CAMSHAFT LOCATION
Flathead or Side Valve
Overhead Valve (OHV)
Overhead Cam (OHC
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ENGINE BLOCK TYPES
In-Line Blocks
V-Type Blocks
Opposed type Blocks:
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ENGINE SYSTEMS
Ignition System.
Fuel System
Emission Control Systems
Exhaust System.
Lubrication system:
Cooling system
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REVIEW OF ENGINE MEASUREMENTS
Bore and Stroke
The bore is thediameter of the
cylinder and ismeasured acrossthe cylinder.
Piston stroke:
It is the distance thatthe piston movesfrom TDC to BDC
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Continue.
Displacement:
The volume of the cylinder between TDC andBDC is referred to as displacement
valve overlap.The crankshaft rotation near TDC on the exhauststroke when both the intake and exhaust valvesare open is called valve overlap.
Compression ratioThe compression ratio is the ratio of the cylinder
volume with the piston at BDC to the cylindervolume with the piston at TDC
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COMPRESSION RATIO
CALCULATION:
If the cylinder volume with the piston at
BDC is 480 cubic centimeters [cc], and the
cylinder volume with the piston at TDC is
60 cc, the compression ratio is 8:1.
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EFFECTS OF COMPRESSION RATIO
Higher compression ratio produce more power thanengines with a lower compression ratio.
The cylinder heat on the compression stroke increasesproportionally.
The fuel may explode rather than burn smoothly in thecombustion chamber.
This exploding action causes detonation
Higher octane fuel reduces this detonation problem to
some extent.The type of fuel recommended by the vehicle
manufacturer is determined largely by thecompression ratio.
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Continue
Compression Ratio for BMW Engine Series
M 43 9.7:1
M54B22 10.8:1
M54B25 10.5:1
M54B30 10.2:1
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FIRING ORDER
The order in which various cylinders of
Multi cylinder engine fire is called the firing
order
4 Cylinder Engine 1 2 4 3 or 1 3 4 2
6 Cylinder Engine1 5 3 6 2 4 or 1 4 2 6 3 5
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ENERGY EFFICIENCY
Thermal Efficiency
Thermal energy is the relationship
between the engine power output and theheat energy available in the fuel. A
percentage is used to express this
relationship.
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Mechanical Efficiency
Mechanical efficiency is the relationship
between the engine power delivered and the
power that would be delivered if the engineoperated without any power loss. The
mechanical efficiency of an engine is expressed
as a percentage.
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Volumetric Efficiency.
Volumetric efficiency is the relationshipbetween the amounts of air actually taken into
the cylinder on the intake stroke compared to theamount of air required to fill the cylinder atatmospheric pressure. Volumetric pressure isalso expressed as a percentage.
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.
Torque and Horsepower
Torque is transferred from the engine
crankshaft through the drive train to the drive
wheels.
Torque = force x distance.
torque is measured in Newton-meters (Nm).
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BASIC ENGINE MECHANICAL
SYSTEM
Crank case
The crankcase is made of Aluminum alloy with
drawn cast iron bushes ( M54)Cast iron crankcase used in M 43 engine
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BLOCK ASSEMBLIES
Cast iron alloy
Aluminum block are becoming more common.
Aluminum block has steel cylinder liners
The aluminum in other block is mixed with silicon
so the silicon accumulates on the cylinder walls
to provide a hard surface that does not require a
sleeve.
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CYLINDER SLEEVES
The cylinder is cast integrally
with the block in most engines.
Heavy-duty engines have
removable dry-type or wet-typereplaceable cylinder sleeves.
A wet-type cylinder sleeve is in
contact with the coolant. This
type of sleeve must be sealedin the block at the top and
bottom
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MAIN BEARING BORES.
The main bearing bores
support the crankshaft in the
block.
The main bearing boresmust be strong enough to
withstand combustion
forces without distorting or
stretching.
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CAMSHAFT BEARING
Camshaft bearing and bearing bores must
support the load of the camshaft and valve train.
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VALVE LIFTER BORES
The valve lifter bores are machined in the block
directly above the camshaft lobes.
Oil is supplied from the main oil gallery in the
block to each valve lifter bore.
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COOLANT JACKETS.
Coolant jackets surround the outside ofeach cylinder wall in the block.
Coolant is circulated through each of thesecoolant jackets to cool the cylinder walls.
A threaded coolant drain plug is positionednear the bottom of the coolant jackets inthe block
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CRANKSHAFTS
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3
1
2 4
5
6
7
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INDEX EXPLANATION
1 Crankshaft
2 Upper bearing shells
3 Lower bearing shells
4 Upper thrust bearing shell
5 Lower bearing shell
6 Incremental gearwheel
7 Ball bearing for gear shaft
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.
The crankshaft changes the vertical piston
movement to rotary motion
Crankshafts may contain cast iron alloy or
forged steel.
All the main bearing and connecting rod bearingjournals are machined to a highly polished finish.
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.
Bearing inserts are located between the main
bearing bores and the main bearing journals on
the crankshaft
Connecting rod bearing inserts are mountedbetween the connecting rod bores and the
crankshaft journals.
Oil passages are drilled from each main bearing
journal to the connecting rod journals to assure
adequate oil supply at the connecting rod
bearings.
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A flex plate, or
flywheel, is bolted to
the transmission end
of the crankshaft and
a vibration damper
and pulley is pressed
onto the front of the
crankshaft
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CONNECTING RODS, PISTONS,
PISTON PINS, AND PISTON RINGS.
Connecting Rod
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Connecting Rod.
Steel-forged, tapered I
beam design.
The connecting rod bore fits
over the crankshaft journal,and the eye in the upper end
of the connecting rod fits
over the piston pin
The connecting rod cap is
bolted to the upper part of
the rod.
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PistonPISTON
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Piston.
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Piston..
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Piston..
Aluminum alloy pistons
The top of the piston is called the head, or
domePiston ring grooves are cut into the sides
of the piston just below the piston head
The ridges between the ring grooves are
referred to as lands
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Piston
Piston must be assembled on the
connecting rods correctly, and the
complete piston and rod
assembly must be installed
properly in the cylinder to
maintain the pin offset in the
correct position
The piston must have sufficientclearance to allow a film of oil
between the piston and the
cylinder wall.
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PISTON PIN.
Piston pins are manufactured from hard steel
Polished exterior surface
One of the most common methods of a mountingthe pin the piston and connecting rod is to pressthe pin into the rod and allow it to rotate in thepiston with a precision clearance
There must be enough clearance between the pinand the piston pin bore or rod bushing to allow afilm of oil between these components.
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PISTON RINGS
The piston rings fit into the piston ringgrooves and provide sealing betweenthe piston and the cylinder walls
Control the amount of oil on the cylinder
walls to prevent excessive amounts ofoil from moving past the rings into thecombustion chamber.
Made from cast iron or nodular iron.
Piston rings may be classified ascompression rings or oil rings. Manypistons have two compression rings inthe upper ring grooves and an oil ring inthe lower groove.
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CAMSHAFT
camshafts are made from a hardened cast ironalloy
A lobe is positioned on the camshaft for each
valve in the engine.The camshaft changes the rotary motion of this
shaft to reciprocating motion of the valves
Marks on the camshaft and crankshaft sprockets
must be properly aligned before the timing chainis installed to time the camshaft in relation to thecrankshaft.
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PARTS OF A CAM LOBE AND A VALVE
TIMING CHART
Parts of a cam lobeA Valve timing chart
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VALVE LIFTERS,PUSH ROD,ROCKER
ARMS AND VALVES
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CYLINDER HEAD
Cylinder heads were made from cast iron
modern engines are usually equipped with
aluminum cylinder heads.
The lower side of the cylinder head contains thecombustion chamber recesses
Threaded openings in the combustion chamber
accept the spark plugs
Coolant passages surround the combustion
chamber and spark plug to provide adequate
cooling.
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CYLINDER HEADS AND INTAKE
MANIFOLD
Warning: The torque on engine bolts is
extremely important, especially on aluminum
components. Improper torque results in warpedcomponents. When servicing an engine, always
follow the torque instructions in the vehicle
manufacturers service manual.
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