CHAPTER 3 INTERNAL COMBUSTION ENGINES

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CHAPTER 3INTERNAL COMBUSTION ENGINES
Again, the study reference is CHAPMANS and the
AUXILIARY study guide.
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INTERNAL COMBUSTION ENGINES
DEFINITION BOTH DIESEL AND GAS CHANGE OR
CONVERT HEAT ENERGY INTO WORK BY BURNING FUEL IN
A CLOSED COMBUSTION CHAMBER. THE PISTONS USE AN
UP-AND-DOWN MOTION. THUS, THEY ARE CLASSIFIED AS
RECIPROCATING ENGINES.
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IGNITION PRINCIPLESGASOLINE ENGINES

1. Uses SPARK IGNITION SYSTEM
2. Called a SPARK IGNITION ENGINE.
3. Fuel and air mixed in a carburetor ( Injection
   chamber if fuel injected).
4. Fuel drawn into cylinders.
5. Fuel/air mixture ignited by electric spark from
   sparkplug(s).

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IGNITION PRINCIPLESDIESEL ENGINES

1. Engine takes atmospheric air and compresses it in
   cylinder head.
2. Injects fuel into combustion space ( cylinder
   head)
3. Fuel injectors. NO carburetors
4. Require extremely CLEAN fuel to properly ignite
5. Compression heating ignites fuel
6. NO SPARK PLUGS

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OPERATING CYCLE

• All reciprocating engines have definite operating
  cycle
• Either 2-Stroke or 4-Stroke
• STROKE Up or Down movement of piston
• Each PISTON completes 2 strokes for each
  revolution of the crankshaft.

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OPERATING CYCLEFOUR STROKE (CYCLE)

1. Each piston goes through 4-strokes
2. Crankshaft has 2 revolutions / one cycle
3. One power stroke per 2 revolutions of crank shaft

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THE OPERATING CYCLE 4-STROKES

1. INTAKE
2. COMPRESSION
3. POWER
4. EXHAUST

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OPERATING CYCLEINTAKE STROKE

1. Intake valve open.
2. Exhaust valve closed.
3. PISTON Moving DOWN.
4. FUEL/AIR MIXTURE Drawn IN through intake valve.

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OPERATING CYCLECOMPRESSION STROKE

1. Both INTAKE and EXHAUST valves CLOSED.
2. PISTON moving UP.
3. Fuel/air mixture is COMPRESSED.
4. Ignition Spark and Compression heating ignites
   mixture.

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OPERATING CYCLEPOWER STROKE

1. INTAKE and EXHAUST valves are CLOSED
2. PISTON moving DOWN
3. CRANKSHAFT TURNS.
4. POWER stroke only time power is translated to
   crankshaft.

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OPERATING CYCLEEXHAUST STROKE

• EXHAUST valve OPEN
• INTAKE valve CLOSED
• PISTON moving UP

THIS ENDS THE 4-STROKE CYCLE The piston
immediately starts down again and the cycle
process starts over.
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OPERATING CYCLETWO STROKE

1. DIESEL ENGINES ARE MOSTLY TWO STROKE
2. GASOLINE ENGINES MOSTLY LIMITED TO OUTBOARDS
3. HAS ONE COMPRESSION AND ONE POWER STROKE

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OPERATING CYCLETWO STROKE (DIESEL)

1. ONE power stroke for each revolution of the
   crankshaft
2. TWICE as many power strokes as in the four-stroke
   engine.
3. Cylinder has exhaust valve but NO INTAKE VALVE.
4. Air comes in through PORTS in cylinder wall
5. 2-STROKE DIESELS GIVE EXCELLENT SERVICE

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FUEL INJECTION SYSTEMSUNIT INJECTOR and COMMON
RAIL

• UNIT INJECTOR Cylinder and plunger in cylinder
  head, sprays or squirts fuel into combustion
  chamber, for ignition. Fuel is INDUCTED from fuel
  tank to fuel injectors under pressure from a
  pump.
• COMMON RAIL Most commonly used. One pump for all
  cylinders. Fuel under pressure from tank to
  cylinder.
• DRAWBACKS System must be purged of all air
  until only fuel comes out. Time consuming,
  awkward and messy.

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CARBURETOR

1. A device used to send a fine spray of fuel into a
   moving stream of air through the intake valves
   into the combustion chamber in the cylinder head
   of the engine.
2. On gasoline engines, used to control the fuel/air
   mixture.

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OPERATING CYCLECOMPRESSION RATIOS

1. With compression ratio in diesel of 141,
   cylinder head temperature 1000ºF. This heat
   ignites the fuel mixture without the spark plug
   ignition.
2. Diesel compression ration are close to 14 1 to
   16 1
3. Gas compression ratios are close to 4 1 to 8 1

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POWER SYSTEM

• Includes the CYLINDERS, PISTONS, CONNECTING RODS
  AND CRANKSHAFT

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POWER SYSTEMCYLINDERS PISTONS - CRANKSHAFTS

1. PISTONS Move up and down in the cylinder
   attached to the crankshaft and transmits power to
   the crankshaft .
2. CYLINDERS Cast in a single engine block with a
   hardened sleeve alloy sleeve to reduce wear.
3. CRANKSHAFT Changes the reciprocating motion of
   the piston and rods into rotary motion of the
   crankshaft which turns the propeller.

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POWER SYSTEMVALVE and CAMSHAFT

1. VALVES Opened by a CAMSHAFT which is driven by a
   CRANKSHAFT.
2. Let fresh air in. Allow combustion gasses to
   vacate.
3. CAMSHAFT Changes rotary to intermittent
   reciprocating motion.

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POWER SYSTEMAIR

1. 4-STROKE (Cycle) Air enters INTAKE VALVE.
2. 2-Stroke (Cycle) Air enters PORTS in cylinder
   wall.

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POWER SYSTEMLUBRICATION

• VITAL TO THE HEALTH OF THE ENGINE
• Delivers oil to moving parts to assist in engine
  cooling and reducing friction.
• Uses a PUMP and FILTER to cleanse and deliver

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COOLING SYSTEMWATER and AIR

1. WATER Holding tank, circulating pump and
   radiator to get rid of the heat in the water.
2. Both SEA and FRESH water are used.
3. FRESH water used with self-contained system.
4. SEA water straight from the environment.

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ELECTRICAL SYSTEMS

1. GENERATOR/ALTERNATOR Produces the electrical
   current to operate the vessels system and charge
   the battery.
2. VOLTAGE REGULATOR Controls the voltage from the
   generator/alternator
3. CUT OUT Keeps the battery from discharging
   through the alternator/generator at low speeds.
4. STARTER An electric motor. Diesel may have
   separate starter motor.
5. Battery Diesels require TWICE the power of gas
   engines.
6. Wiring harness Carries the electrical current.

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IGNITION SYSTEM(S)

1. Ignition COIL
2. Mechanical Breaker
3. Condenser
4. Distributor
5. Spark Plug(s)
6. Switch
7. Wiring

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IGNITION SYSTEM COMPONENTS

1. IGNITION COIL The generated power source (FOR
   THE SPARK IN THE SPARK PLUG)
2. MECHANICAL BREAKER(POINTS) Break the current at
   proper time
3. CONDENSER Prevents arcing when the points are
   open.
4. DISTRIBUTOR Serves as a selector switch to
   distribute the current to the individual spark
   plugs (gas engine only)
5. SPARK PLUG(S) ( Gasoline engines only)Provided
   the fire to ignite the fuel in the combustion
   chamber. (Spark comes from the COIL, NOT the
   battery)

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PRIMARY IGNITION CIRCUIT(LOW VOLTAGE)

• GASOLINE ENGINE
• Battery
• Ignition switch
• Ignition coil (Low side)
• Breaker points ( in distributor)
• condenser

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SECONDARY IGNITION CIRCUIT(HIGH
VOLTAGE)GASOLINE ENGINE

1. DISTRIBUTOR (ROTOR)
2. IGNITION COIL (HIGH SIDE)
3. SPARK PLUGS

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TROUBLE SHOOTING
GAS ENGINES REQUIRE 1. CORRECT FUEL-AIR
MIXTURE 2. GOOD COMPRESSION 3. GOOD
SPARK DIESEL ENGINES REQUIRE 1. CORRECT FUEL
PRESSURE 2. HIGH COMPRESSION 3. NO AIR IN
FUEL LINE(S)
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REVIEW QUESTIONS NO.1

• All reciprocating engines have a definite cycle
  of operation and __________________
• operate on either a 2-stroke or 4-stroke cycle.
• the number of cycles depends on the number of
  cylinders.
• the 2-stroke cycle is used only in diesel engines
  since 4-stroke cycle is required for proper
  function of a gasoline engine.
• the number of valves used for exhaust determine
  the operating cycle.

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REVIEW QUESTIONS

• All reciprocating engines have a definite cycle
  of operation and ________________
• a. operate on either a 2-stroke or 4-stroke
  cycle.

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REVIEW QUESTIONS NO. 2
2. The cam shaft_____________________ a. drives
the propeller. b. carries cams that are usually
square in shape. c. is used to rotate the cams
that open the valves. d. changes reciprocating
motion to rotary motion .
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REVIEW QUESTIONS
2. The cam shaft ______________________ c. is
used to rotate the cams that open the valves.
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REVIEW QUESTIONS NO. 3
3. Diesel engines have high compression ratios,
in the range of 161 to 201, in order
to_________ a. easily exhaust heavy diesel
fuel. b. provide maximum power in the intake
stroke. c. compress air to generate heat for
fuel ignition. d. assist the entrance of fuel
from the carburetor.
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REVIEW QUESTIONS
3. Diesel engines have high compression ratios,
in the range of 161 to 201 in order
to______________ c. compress air to generate
heat for fuel ignition
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REVIEW QUESTIONS NO. 4
4. A 2-stroke engine______________ a. has a
compression and a power stroke. b. is only used
in diesel engines c. has twice the power in very
large gasoline engines d. is so designated
because there is a cycle of 2-strokes
between the opening and closing of the exhaust
valves of each cylinder.
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REVIEW QUESTIONS
4. A 2-stroke engine________________ a. has a
compression and a power stroke.
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REVIEW QUESTIONS NO. 5
5. In a diesel engine, fuel__________________ a.
is injected directly into the cylinder or
combustion chamber b. is mixed with air, then
injected into the cylinder c. is also used for
lubrication d. consumption is constant at all
speeds
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REVIEW QUESTIONS
5. In a diesel engine, fuel ________________ a.
is injected directly into the cylinder or
combustion chamber.
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REVIEW QUESTIONS NO. 6
6. In a gasoline engine the fuel-air mixture
ratio is controlled by the _________ a.
throttle b. carburetor c. intake valve d. fuel
pump
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REVIEW QUESTIONS
6. In a gasoline engine the fuel-air mixture
ratio is controlled by the ____________________
b. carburetor
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REVIEW QUESTIONS NO. 7
7. Lubricating oil in engines_______ a. is used
for ignition and for friction reduction b. is
used only to lubricate the bearings and
bushings c. is always under constant
pressure d. is used to reduce friction and
increase cooling.
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REVIEW QUESTIONS
7. Lubricating oil in engines ______________ d.
is used to reduce friction and increase cooling
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REVIEW QUESTIONS NO. 8
8. Which of the following groups of items are
common to both diesel and 4-cycle gasoline
engines? a. valves, carburetor and fuel
pumps b. valves, pistons and spark plugs c.
valves, cylinders and fuel pumps d. valves,
distributor and carburetor
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REVIEW QUESTIONS
8. Which of the following groups of items are
common to both the diesel and 4-cycle gasoline
engine? c. valves, cylinders and fuel pump
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REVIEW QUESTIONS NO. 9
9. The primary circuit of the ignition system for
gasoline engines includes the ________ a.
distributor and breaker points b. battery and
spark plugs c. ignition coil and breaker
points d. ignition coil and distributor
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REVIEW QUESTIONS
9. The primary circuit of the ignition system for
gasoline engines includes the _____________ c.
ignition coil and breaker points
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REVIEW QUESTIONS NO. 10
10. The high voltage that produces the spark in
the spark plug in a gasoline engine is produced
in the _____________________ a. battery b.
condenser c. breaker points d. ignition coil
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REVIEW QUESTIONS
10. The high voltage that produces the spark in
spark plug in a gasoline engine is produced in
the ___________________ d. ignition coil