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					               CHAPTER 3
INTERNAL COMBUSTION ENGINES

Again, the study reference is CHAPMAN’S and the
AUXILIARY study guide.
    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.
          IGNITION PRINCIPLES
                  GASOLINE 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).
          IGNITION PRINCIPLES
                       DIESEL 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
           OPERATING CYCLE
1. All reciprocating engines have definite operating cycle
2. Either 2-Stroke or 4-Stroke
3. STROKE: Up or Down movement of piston
4. Each PISTON completes 2 strokes for each revolution
   of the crankshaft.
            OPERATING CYCLE
               FOUR 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
      THE OPERATING CYCLE
                 4-STROKES

1. INTAKE
2. COMPRESSION
3. POWER
4. EXHAUST
              OPERATING CYCLE
                      INTAKE STROKE

1.   Intake valve open.
2. Exhaust valve closed.
3. PISTON: Moving DOWN.
4. FUEL/AIR MIXTURE: Drawn IN through intake valve.
            OPERATING CYCLE
              COMPRESSION 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.
           OPERATING CYCLE
                  POWER 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.
           OPERATING CYCLE
                 EXHAUST STROKE
1. EXHAUST valve OPEN
2. INTAKE valve CLOSED
3. PISTON moving UP

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

1. DIESEL ENGINES ARE MOSTLY TWO STROKE
2. GASOLINE ENGINES MOSTLY LIMITED TO
   OUTBOARDS
3. HAS ONE COMPRESSION AND ONE POWER
   STROKE
             OPERATING CYCLE
                TWO 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
    FUEL INJECTION SYSTEMS
  UNIT INJECTOR and COMMON RAIL
1. 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.
2. 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.
                 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.
             OPERATING CYCLE
               COMPRESSION RATIOS

1. With compression ratio in diesel of 14:1, 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
          POWER SYSTEM
Includes the CYLINDERS, PISTONS, CONNECTING
              RODS AND CRANKSHAFT
               POWER SYSTEM
       CYLINDERS – 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.
               POWER SYSTEM
               VALVE 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.
               POWER SYSTEM
                           AIR


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

      VITAL TO THE HEALTH OF THE ENGINE


1. Delivers oil to moving parts to assist in engine cooling
   and reducing friction.
2. Uses a PUMP and FILTER to cleanse and deliver
             COOLING SYSTEM
                    WATER 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.
         ELECTRICAL SYSTEMS
1. GENERATOR/ALTERNATOR: Produces the electrical current
   to operate the vessel’s 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.
            IGNITION SYSTEM(S)
1. Ignition COIL
2. Mechanical Breaker
3. Condenser
4. Distributor
5. Spark Plug(s)
6. Switch
7. Wiring
  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)
  PRIMARY IGNITION CIRCUIT
       (LOW VOLTAGE)
                 GASOLINE ENGINE
1. Battery
2. Ignition switch
3. Ignition coil (Low side)
4. Breaker points ( in distributor)
5. condenser
SECONDARY IGNITION CIRCUIT
     (HIGH VOLTAGE)
             GASOLINE ENGINE

1. DISTRIBUTOR (ROTOR)
2. IGNITION COIL (HIGH SIDE)
3. SPARK PLUGS
        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)
     REVIEW QUESTIONS NO.1
1. All reciprocating engines have a definite cycle
   of operation and __________________
  a. operate on either a 2-stroke or 4-stroke cycle.
  b. the number of cycles depends on the number of cylinders.
  c. the 2-stroke cycle is used only in diesel engines since 4-
     stroke cycle is required for proper function of a gasoline
     engine.
  d. the number of valves used for exhaust determine the
     operating cycle.
    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 .
    REVIEW QUESTIONS NO. 3
3. Diesel engines have high compression ratios, in
the range of 16:1 to 20:1, 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.
    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.
    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
     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
    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.
    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
     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
    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
END CHAPTER 3

				
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