CCAS 3381 AUTOMOTIVE SKILL I

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CCAS 3381 AUTOMOTIVE SKILL I

• ENGINE SUBSYSTEMS

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OBJECTIVES

• To understand the operational principles and
  basic mechanisms of engine sub-systems

Lecture 1 hour 15 mins Workshop 45 mins
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LUBRICATION SYSTEM (1)

• Makes sure every moving part in the engine gets
  oil so that it moves easily especially
• Pistons (so they can slide easily in their
  cylinders)
• Any bearings that allow things to rotate freely
• Oil is sucked out of the oil pan by oil pump, run
  through oil filter to remove any grit squirted
  under high pressure onto bearings the cylinder
  walls before trickling down into the sump

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LUBRICATION SYSTEM (2)

• Piston rings - provide a sliding seal between the
  outer edge of the piston and the inner edge of
  the cylinder
• Prevent the fuel/air mixture and exhaust in the
  combustion chamber from leaking into the sump
• Keep oil in the sump from leaking into the
  combustion area, where it would be burned and
  lost
• Cars that "burn oil" have to top up engine oil
  every 1,000 miles are burning it because the
  rings no longer seal things properly (stinky
  bluish/whitish smoke)

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LUBRICATION SYSTEM (3)

• Whitish engine oil due to leaked gasket coolant
  mixed with engine oil

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LUBRICATION SYSTEM (4)

• SAE 10W-30, SAE 20W-50 (mineral)
• SAE 0W-30 (synthetic)

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FUEL EXHAUST SYSTEM (1)

• Pumps petrol from the tank and mixes it with air
  so that the proper air/fuel (A/F) mixture flows
  into the cylinders by either
• carburetion,
• port fuel injection
• direct fuel injection
• 10 mg of gasoline per combustion stroke is needed
  during each cycle
• Carburetor mixes just the right amount of
  gasoline with air (not too lean/too rich)

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FUEL EXHAUST SYSTEM (2)
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FUEL EXHAUST SYSTEM (3)
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FUEL EXHAUST SYSTEM (3)

• Valves - intake exhaust valves open at the
  proper time to let in A/F to let out exhaust
  (both valves are closed during compression and
  combustion so that the combustion chamber is
  sealed)
• Exhaust system - includes exhaust pipe, muffler
  to reduce noise a catalytic converter

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COOLING SYSTEM (1)

• IC engines waste 70 of the chemical energy in
  petrol as heat
• Engine cooling system must remove this heat to
  prevent overheating
• Engine runs best at a fairly high temperature
  (93oC)

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COOLING SYSTEM (2)

• In cold engine, components wear out faster, is
  less efficient emits more pollution
• Cooling system allows engine to heat up as
  quickly as possible then keep it at a constant
  temperature

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COOLING SYSTEM (3)

• Liquid Cooling
• circulates a fluid through pipes and passageways
  in the engine, absorbs heat, cooling the engine
• The fluid leaves the engine, passes the radiator
  which transfers the heat from the fluid to the
  air blowing
• Water pump (driven by belt connected to
  crankshaft) sends the fluid into the engine block
• Thermostat opened water goes to radiator
  thermostat closed fluid back to pump engine
• Auto cars have separate circuit for cooling
  transmission fluid built into the radiator

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COOLING SYSTEM (4)

• Radiator cap increases the boiling point of your
  coolant by about 25oC
• Cooling fan controlled to maintain engine
  constant temperature (FWD - electric fan
  controlled by thermostatic switch or ECU)
• Water - most effective fluids for holding heat,
  (most cars use mixture of water and ethylene
  glycol (C2H6O2) also known as antifreeze

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COOLING SYSTEM (5)
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IGNITION SYSTEM (1)

• Ignition oil - generates high voltages to create
  a spark (current flows from battery through
  primary winding suddenly disrupted by breaker
  points to 100,000 V

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IGNITION SYSTEM (2)

• Distributor - distribute the high voltage from
  the coil to correct cylinder
• Spark timing - critical to an engine performance
• Spark advance (high speeds) spark retard
  (idling low speeds)

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IGNITION SYSTEM (3)

• Spark plug - spark plug supplies spark that
  ignites the A/F
• forces electricity to arc across a gap
• must have insulation
• Must withstand extreme heat pressure (plug tip
  burns deposits)
• must happen at just the right moment for things
  to work properly

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Distributor-less ignitions have a coil for each
spark plug, located directly on the spark plug
itself no spark cables no distributors
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THE END
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