© goodheart-willcox co., inc. permission granted to reproduce for educational use only publisher...
TRANSCRIPT
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Publisher
The Goodheart-Willcox Co., Inc.Tinley Park, Illinois
by
Russell Krick
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Engine operation Engine bottom end Engine top end Engine front end
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The engine is the source of power for the vehicle
It converts the energy stored in fuel into motion
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Fuel is burned inside the engine’s combustion chamber to produce heat
Heat causes expansion of gases in the engine
Expansion in the combustion chamber produces pressure
Engine components convert pressure into rotating motion
Engine Operation
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Engine Operation
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Piston Travel(TDC, BDC)
Top dead center (TDC)piston is at its highest point in the cylinder
Bottom dead center (BDC)piston is at its lowest point in the cylinder
Piston strokedistance the piston slides up or down
from TDC to BDC
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Piston Travel
(TDC, BDC)
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Four-Stroke Cycle Requires four piston strokes to
complete one cycle Every four strokes, the engine
produces one power stroke Two complete crankshaft rotations are
required to complete the four-stroke cycle
Almost all automobiles use four-stroke-cycle engines
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Intake Stroke Draws fuel and air into the engine Intake valve is open Exhaust valve is closed Piston slides down and forms a low
pressure area in the cylinder Atmospheric pressure pushes the air-
fuel mixture into the cylinder
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Compression Stroke
Compresses (squeezes) the air-fuel mixture, making it more combustible
Piston slides upward Both valves are closed
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Power Stroke Burns the air-fuel mixture and pushes
the piston down with tremendous force Both valves are closed Spark plug fires, igniting the air-fuel
mixture Pressure forms on the top of the piston Piston is forced down, rotating the
crankshaft
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Exhaust Stroke Removes the burned gases from the
cylinder Piston moves upward Intake valve is closed Exhaust valve is open Burned gases are pushed out the
exhaust port
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Four-Stroke Cycle
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Refers to the block, crankshaft, connecting rods, pistons, and related components
Another name for the bottom end is the short block
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Engine Block
Forms the main body of the engine
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Engine Block Parts Cylinders
large, round holes machined through the block
Water jackets coolant passages through the blockallow a solution of water and antifreeze to
cool the cylinders
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Engine Block Parts Core (freeze) plugs
round metal plugs that seal holes left in the block after casting
Main bearing boresholes machined in the bottom of the block
to hold the crankshaft Main caps
hold the crankshaft and main bearing inserts in place
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Crankshaft
Harnesses the tremendous force produced by the downward thrust of the pistons
Changes the reciprocating (up-and-down) motion of the pistons into rotating motion
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Fits into the bottom of the block
Crankshaft
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Journals are precision-ground surfaces for the bearings
Crankshaft Parts
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Crankshaft Parts
Counterweight offsets the weight of the piston, rod, rings, and journal offset to prevent vibration
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Crankshaft snout sticks through the front of the blockprovides a mounting place for the
camshaft drive mechanism, front damper, and pulleys
Crankshaft flangeholds the flywheel
Crankshaft Parts
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Removable inserts that fit between the block main bore and the crankshaft main journals
One-half of each insert fits into the block, while the other half fits into the block main cap
A main thrust bearing has flanges to control crankshaft end play
Engine Main Bearings
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Engine Main Bearings
Oil holes and grooves allow oil to lubricate the bearings
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Main Bearing Clearance
Space between the crankshaft main journal and the main bearing insert
Allows lubricating oil to enter and separate the journal and bearing this allows the journal to rotate without
rubbing on the bearing and causing excess wear
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Engine Bottom End
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Crankshaft Oil Seals Keep oil from leaking out the front and
rear of the engine Seals are placed around the front and
rear of the crankshaft to contain this oil Rear main oil seal
one- or two-piece seal that fits around the rear of the crankshaft to prevent oil leakage
Front main oil sealone-piece seal pressed into the front
cover
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Flywheel Large metal disk mounted on the rear
of the crankshaft Flywheel functions:
connects the crankshaft to the transmission or transaxle through a clutch or torque converter
helps smooth engine power pulses contains a large ring gear, which meshes
with the starting motor gear to start the engine
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Connecting Rod
Fastens the piston to the crankshaft Transfers piston movement and
combustion pressure to the crankshaft rod journals
Causes piston movement during the non-power producing strokes intake, compression, and exhaust
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Connecting Rod
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Connecting Rod Bearings
Ride on the crankshaft rod journals Fit between the connecting rods and
the crankshaft Rod bearing clearance
small space between the rod bearing and crankshaft journal
allows oil to enter the bearing, preventing metal-to-metal contact
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Piston
Transfers the pressure of combustion to the connecting rod and crankshaft
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Piston (Wrist) Pin
Allows the piston to swing on the connecting rod
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Piston Clearance The amount of space between the
sides of the piston and the cylinder wall Allows a lubricating film of oil to form
between the piston and the cylinder Allows for expansion when the piston
heats up
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Piston Rings Seal the clearance between the outside
of the piston and the cylinder wall Keep combustion pressure from
entering the crankcase Keep oil from entering the combustion
chambers
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Piston Rings
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Compression Rings
Prevent blowby (compression pressure leaking into the engine crankcase)
Compression and combustion pressure push the compression rings down in their grooves and out against the cylinder wall, improving sealing
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Compression Rings
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Oil Rings Prevent engine oil from entering the
combustion chamber Scrape excess oil off the cylinder wall If too much oil gets into the combustion
chamber, it will burn, causing blue exhaust smoke and increased exhaust emissions
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Oil Rings
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Ring Gap Split, or space, between the ends of a
piston ring Allows the ring to be spread open and
installed on the piston Allows the ring to be made slightly
larger in diameter than the cylinderwhen installed in the cylinder, the ring
spreads outward and presses on the cylinder wall, aiding ring sealing
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Refers to the cylinder heads, valves, camshaft, and other related components
These parts work together to control the flow of air and fuel into the engine cylinders
They also control the flow of exhaust out of the engine
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© Goodheart-Willcox Co., Inc. Permission granted to reproduce for educational use only
Bolts to the deck of the cylinder block Covers and encloses the top of the
cylinders Combustion chambers are small
pockets formed in the cylinder head combustion occurs in these small pockets
Cylinder Head
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Cylinder Head
Combustion chambers contain the spark plug tip and valve seats
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Cylinder Head Parts Intake ports
route air (diesel engine) or air and fuel (gasoline engine) into the combustion chamber
Exhaust ports route burned gases out of the combustion
chamber
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Cylinder Head Parts Valve guides
small holes machined through the cylinder head for the valves
valves slide in these guides Valve seats
machined surfaces in the combustion chamber port openings
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Cylinder Head Parts
When the valve is closed, it sealsagainst the valve seat
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Valve Train
Consists of the valves and the partsthat operate them
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Valve Train Operation
The camshaft lobe turns into the lifter and the valve
is pushed open
The lobe rotates away from the lifter and the valve spring
pushes the valve closed
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Camshaft
Located in the engine block or in the cylinder head
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Camshaft Parts Cam lobes
egg-shaped protrusions machined on the camshaft
one lobe is provided for each engine valve
Eccentricmay be machined on the camshaft for a
mechanical fuel pump Camshaft journals
machined surfaces for the cam bearings
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Valve Lifters Usually rides on the cam lobes and
transfers motion to the rest of the valve train
Located in the engine block or cylinder head
Fit into lifter bores, which are machined holes in the block or head
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Push Rods Transfer motion between the lifters and
the rocker arms Needed when the camshaft is located
in the cylinder block Made from a hollow metal tube with a
ball or socket formed on each end One end fits into the lifter, while the
other end fits against the rocker arm
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Rocker Arms Used to transfer motion to the valves Mount on top of the cylinder head Rocker arm movement allows the
camshaft lobe to force the valve open Valve spring force closes the valve and
keeps the rocker arm in contact with the push rod
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Valves
Open and close the ports inthe cylinder head
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Intake Valve Larger than the exhaust valve Controls the flow of the air-fuel mixture
(gasoline engine) or air (diesel) into the combustion chamber
Fits into the port leading from the intake manifold
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Exhaust Valve
Controls the flow of exhaust gases out of the cylinder
Smaller than the intake valve Fits into the port leading to the exhaust
manifold
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Valve Seals
Prevent oil from entering the combustion chambers through the valve guides
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Valve Spring Assembly
Used to close the valve
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Intake Manifold
Bolts to the side of the cylinder head Contains runners going to each
cylinder head port Air and fuel (gasoline engine) are
routed through these runners
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Exhaust Manifold
Bolts to the cylinder head Fastens over the exhaust ports to carry
burned gases to the exhaust system Made of cast iron, lightweight
aluminum, or stainless steel tubing
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Engine Manifolds
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Valve (Rocker) Cover
Thin metal or plastic cover over the top of the cylinder head
Keeps valve train oil spray from leaking out of the engine
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Operates the engine camshaft and sometimes the oil pump, distributor, engine sensors, and diesel injection pump
Consists of a drive mechanism, a front cover, an oil seal, and a crankshaft damper
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Camshaft Drive
Needed to turn the camshaft at one-half engine speed
Often called the timing belt, timing chain, or timing gears because they time the camshaft with the crankshaft
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Camshaft Drive
A belt-drive, chain-drive, or gear-drivemay be used to turn the camshaft
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Front Cover Bolts over the crankshaft snout Holds an oil seal that seals the front of
the crankshaft When the engine uses a gear- or
chain-type camshaft drive, the front cover may be called the timing cover
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Engine Front End
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Timing Belt
The front cover houses the front oil seal. The timing cover fits over the belt.
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Timing Chain
Timing chain and sprockets operate
the camshaft in this engine
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Crank Damper Heavy wheel on the crankshaft snout Mounted in rubber Helps prevent crankshaft vibration and
damage Also called the harmonic balancer or
vibration damper