ccas 3381 automotive skill i engine subsystems. objectives to understand the operational principles...

CCAS 3381 CCAS 3381 AUTOMOTIVE SKILL IAUTOMOTIVE SKILL I

ENGINE SUBSYSTEMS

OBJECTIVESOBJECTIVESTo understand the operational

principles and basic mechanisms of engine sub-systems

Lecture – 1 hour 15 minsWorkshop – 45 mins

LUBRICATION SYSTEM (1)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

LUBRICATION SYSTEM (2)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 lostCars 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)

LUBRICATION SYSTEM (3)LUBRICATION SYSTEM (3) Whitish engine oil due to leaked gasket –

coolant mixed with engine oil

LUBRICATION SYSTEM (4)LUBRICATION SYSTEM (4) SAE 10W-30, SAE 20W-50 (mineral) SAE 0W-30 (synthetic)

FUEL & EXHAUST SYSTEM (1)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)

FUEL & EXHAUST SYSTEM (2)FUEL & EXHAUST SYSTEM (2)

FUEL & EXHAUST SYSTEM (3)FUEL & EXHAUST SYSTEM (3)

FUEL & EXHAUST SYSTEM (3)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

COOLING SYSTEM (1)COOLING SYSTEM (1) IC engines waste 70% of the chemical

energy in petrol as heatEngine cooling system must remove

this heat to prevent overheating Engine runs best at a fairly high

temperature (93oC)

COOLING SYSTEM (2)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

COOLING SYSTEM (3)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 blockThermostat opened – water goes to radiator & thermostat

closed – fluid back to pump & engineAuto cars have separate circuit for cooling transmission

fluid built into the radiator

COOLING SYSTEM (4)COOLING SYSTEM (4)Radiator cap increases the boiling

point of your coolant by about 25oCCooling 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

COOLING SYSTEM (5)COOLING SYSTEM (5)

IGNITION SYSTEM (1)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

IGNITION SYSTEM (2)IGNITION SYSTEM (2)Distributor - distribute the high voltage

from the coil to correct cylinderSpark timing - critical to an engine

performance–Spark advance (high speeds) & spark

retard (idling & low speeds)

IGNITION SYSTEM (3)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

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

& no distributors

THE ENDTHE ENDIQ + EQ + SQ = TQ*