2. Objectives (1 of 2)
• Upon completion and review of this chapter, you should be able
to:
– Define the methods used for engine classification.
– Describe the four strokes in the four-stroke engine.
– Explain compression ratio.
– Explain the purpose of the camshaft, pushrods, and rocker arms.
– Explain volumetric efficiency.
– Describe the difference between an overhead cam and an
overhead valve engine.
– Describe the different types of engine block design.
– Briefly describe the different engine systems.
– Define cylinder bore and stroke.
3. Objectives (2 of 2)
• Upon completion and review of this chapter, you should be able
to:
– Explain how to calculate engine displacement.
– Describe three different methods of measuring engine efficiency.
– Name and describe the components of a typical lubricating
system.
– Describe the purpose of a crankcase ventilation system.
– Explain oil service and viscosity ratings.
– List and describe the major components of the cooling system.
– Describe the function of the water pump, radiator, radiator cap,
and thermostat in the cooling system.
4. Introduction
• Modern engines are highly engineered power
plants.
• Modern engines are:
– Compact
– Lightweight
– Fuel efficient
5. Engine Classifications
• Operational cycles
• Number of cylinders
• Cylinder arrangement
• Displacement
• Valvetrain type
• Ignition type
• Cooling system
• Fuel type
11. 4-Stroke Operation
Intake Valves Exhaust Valves
• The four strokes
– Intake stroke
– Compression stroke
– Power stroke
– Exhaust stroke
12. 4-Stroke Operation
• The four strokes
– Intake stroke
– Compression stroke
– Power stroke
– Exhaust stroke
13. Intake Stroke
• Piston moves
downward.
• Intake valve is open.
• Exhaust valve is closed.
• Expanding volume
creates low pressure in
the cylinder allowing
atmospheric pressure to
force in air/fuel mixture.
14. Compression Stroke
• Piston moves upward.
• Both valves are closed.
• Pressure in the
combustion chamber
rises.
15. Power Stroke
• Piston moves
downward.
• Both Valves are closed.
• Ignition occurs, igniting
the air fuel mixture.
• The heat from
combustion increases
pressure in the
cylinder, forcing the
piston downward.
16. Exhaust Stroke
• Piston moves upward.
• Intake valve is closed.
• Exhaust valve is open.
• Exhaust gasses from
combustion are forced
out of the cylinder
through the exhaust
valve.
21. That Thing Got a Hemi®?
•Disadvantages of a Hemispherical
Combustion Chamber
•Limited to Two Valves/Cylinder
•Large Combustion Chamber
22. Power Impulses
• A four-cylinder engine has one cylinder on a power
stroke every 180 degrees of crankshaft rotation.
• The more cylinders, the more power impulses and
the smoother the engine will run.
23. In-Block Valves – Flathead
• Old design that is no
longer used.
• Flathead
36. Engine Efficiency
• Thermal efficiency
– 35% loss to cooling and lubrication systems
– 35% loss to exhaust gasses
– 5% loss to engine friction
– 10% loss to powertrain friction
• Mechanical efficiency
• Volumetric efficiency
37. Torque and Horsepower (1 of 2)
• Torque = Force x Radius
• Brake horsepower
– The useable power at the engine’s crankshaft
• Friction horsepower
– The power required to overcome the internal
friction of the engine
38. Torque and Horsepower (2 of 2)
• There exists a relationship
between horsepower and
torque
• HP and Torque are always
equal at 5,252 RPM.
• HP = (Torque x RPM)/5252
40. Atkinson Engine
• By using levers, all four
strokes are achieved
with one crankshaft
revolution.
• The power stroke is
longer than the intake
stroke, which improves
fuel efficiency.
42. Two-Stroke Gasoline Operation
• As the piston moves
upward, the expanding
volume in the
crankcase creates a
lower pressure area
which draws the air/fuel
mixture into the
crankcase.
44. Two-Stroke Gasoline Operation
• Continuing downward,
the intake port is
exposed and the
air/fuel mixture is forced
into the combustion
chamber,
simultaneously forcing
out the exhaust gasses.
45. Two-Stroke Gasoline Operation
• As the piston moves
upward, the intake and
exhaust ports are
sealed-off by the piston
and the air/fuel mixture
is compressed.
• (Also remember that
the next air/fuel mixture
is simultaneously being
drawn into the
crankcase).
46. Two-Stroke Gasoline Operation
• The spark plug ignites
the air/fuel mixture,
forcing the piston
downward, and
continuing the cycle.
47. Four-Stroke Diesel
• 4 strokes are the same
as the gasoline 4-stroke.
• Compression ignition
instead of spark ignition.
48. Two-Stroke Diesel Operation
With Exhaust Port With Exhaust Valve
• May or may not have
an exhaust valve.
• Must have a blower
(supercharger) to run.
• Commonly used by
Detroit Diesel®.
53. Miller-Cycle Engine
• A Miller-cycle engine depends on a
supercharger.
• A Miller-cycle engine leaves the intake
valve open during part of the compression
stroke, so that the engine is compressing
against the pressure of the supercharger
rather than the pressure of the cylinder
walls. The effect is increased efficiency, at
a level of about 15 percent.
Source: http://auto.howstuffworks.com/question132.htm
55. Hybrid Engines
• Hybrid – Two power
sources
– Usually gasoline and
electricity
• Electricity is usually
used during low-speed,
low torque conditions
• Gasoline is used during
high-speed, high-torque
conditions
89. General Diagnostic Procedure
• The key to diagnostics is to know:
– What test to conduct
– When to conduct a test
• To know this you must understand:
– The system
– The test
90. Engine Leak Diagnosis
• Fuel leak diagnosis
• Engine oil leak diagnosis
– Dye can be used with a black-light for hard-to-
find leaks.
• Engine coolant leak diagnosis
– Use a cooling system pressure tester to
pressurize the system.
91. Engine Noise Diagnosis (1 of 2)
• Main bearing noise
• Connecting rod bearing noise
– Will be greater under load
– Disconnect sparkplug wire from each cylinder and
listen for noise to diminish
• Piston slap
– Usually heard at when engine is first started (cold)
and diminishes as engine warms up.
• Piston pin noise
• Piston ring noise
• Ring ridge noise
92. Engine Noise Diagnosis (2 of 2)
• Valvetrain noise and camshaft noise
– These noises will be half the frequency of
engine speed
• Combustion noises
– Spark knock
– Check ignition timing and fuel quality
• Flywheel and vibration damper noise
93. Engine Exhaust Diagnosis
• Exhaust smoke
– Blue smoke indicates excessive oil
consumption.
– Black smoke indicates a rich air-fuel mixture.
– Light gray/white smoke indicates coolant leak.
• Exhaust noise
– Minor leaks can sound like a ticking noise
94. Diagnosis of Oil consumption
• Excessive oil consumption may be caused
by:
– External leaks
– Combustion chamber leaks
• Usually rings
– Plugged PCV system
95. Engine Oil Pressure Tests
• Oil pressure test gauge
connected to the
opening of the oil
pressure gauge
sending unit
96. Engine Temperature Tests
• Thermostat
• Belts and hoses
• Radiator
• Radiator shroud
• Radiator cap
• Cooling system pressure test
• Antifreeze protection
• Cooling fan
98. Exhaust Gas Analyzer (1 of 3)
• Looks at the results of the combustion
process
• Measures
– Hydrocarbons (HC)
– Carbon monoxide (CO)
– Carbon dioxide (CO2)
– Oxygen (O2)
– Oxides of nitrogen (NOx)
99. Exhaust Gas Analyzer (2 of 3)
• Quick tests using the exhaust analyzer
– Engine manifold vacuum leaks
– Leaking injectors
– Fuel combustion efficiency test
– Contaminated motor oil test
– PCV test
– Air injection reaction (AIR) test
100. Exhaust Gas Analyzer (3 of 3)
– General emissions test
– Fuel enrichment test
– Combustion chamber leaks
– Locating a fuel leak
– Excessive valve guide wear
101. Engine Power Balance Test
• Checks the efficiency of individual cylinders
• May be used to identify the problem cylinder
• Disables each cylinder individually
• The cylinder that drops the least RPM is
contributing the least amount of power.
102. Compression Tests
• Compression test
– Checks the sealing ability of
• The rings
• The valves
• The combustion chamber
• Wet compression test
– Determines if the leak is from the rings or valves
• Running compression test
– Tests the cylinder’s volumetric efficiency
103. Cylinder Leakage Test (1 of 2)
• Determines where the leak is
– The rings
• Air will leak out oil cap
– The valves
• Air will leak through the throttle body if the intake
valve is not sealing
• Air will leak through the tailpipe if the exhaust valve
is leaking
– The combustion chamber
• Usually a bad head gasket
• Could be a cracked cylinder head or block
104. Cylinder Leakage Test (2 of 2)
• During a cylinder leakage test, air may be felt or be
heard leaking from these areas.
105. Valve Timing Checks
• Checks to determine if the camshaft is in time
with the crankshaft
– The timing chain or belt may have jumped a
tooth due to excessive wear
106. Valve Adjustment (1 of 2)
• Required as maintenance on engines that
use mechanical valve lifters
• Not required as maintenance on engines that
use hydraulic lifters
• Should be done on any engine if the valve
train components are worn or have been
improperly serviced
107. Valve Adjustment (2 of 2)
• Measuring the valve
clearance between the
camshaft and the
rocker arm
