CCAS 3381 AUTOMOTIVE SKILL I INTERNAL COMBUSTION (IC) ENGINE

OBJECTIVES To understand the operational principles and basic mechanisms of the internal combustion engine Lecture – 1 hour Workshop – 1 hour

ENGINE BASICS (1) Purpose of an IC engine –to convert fuel (petrol, diesel, NGV) into motion to move your car by burning the fuel inside an engine (internal combustion engine) There are different kinds of IC engines –Spark ignition (SI) or petrol engine –Compression ignition (CI) or diesel engines –Rotary engines –Two-stroke engines (motorbikes) –Each has its own advantages and disadvantages

ENGINE BASICS (2) Combustion is key!!! Rotary engine (Mazda R7)

Most cars use a four-stroke combustion cycle which consists of: –Intake stroke - piston starts at top, intake valve opens & piston moves down to let the engine take in a cylinder-full of air and fuel (A/F) –Compression stroke - the piston moves back up to compress this A/F. Compression makes the explosion more powerful –Combustion stroke - the piston reaches the top of its stroke, spark plug emits a spark to ignite A/F & explodes driving piston down –Exhaust stroke - the piston hits the bottom of its stroke, exhaust valve opens & exhaust leaves cylinder to go out tail pipe ENGINE BASICS (3)

ENGINE BASICS (4)

ENGINE BASICS (5) Core of engine is cylinder - piston moving up and down inside the cylinder (one cylinder) Inline V Boxer Engine configurations

Combustion chamber - area where compression & combustion take place (size of combustion chamber changes) Difference between max. & min. is called the displacement (measured in liters or CCs) In a 4-cylinder engine, each cylinder displaces half a liter, then the entire engine is a "2.0 liter engine" A 2.0 liter engine is roughly half as powerful as a 4.0 liter engine Displacement (& power) can be increased by increasing no. of cylinders or by making the combustion chambers of all the cylinders bigger (or both) ENGINE BASICS (6)

Movement of piston from top to bottom - stroke Top position – top dead center (TDC) Bottom position – bottom dead center (BDC) IC engine requires four sub-systems in order to sustain its operations (details are covered in engine sub-systems) –Cooling system –Lubrication system –Fuel (& exhaust) system –Ignition system ENGINE BASICS (7)

ENGINE BASICS (8)

TDC BDC CLEARANCE VOLUME DISPLACEMENT VOLUME ENGINE BASICS (9)

ENGINE BASICS (10) Engine Control Unit

What Can Go Wrong? –Three fundamentals: Bad fuel mix Lack of compression Lack of spark (Beyond these, thousands of minor things can create problems) –Bad fuel mix No petrol Air intake clogged (petrol but no air) Fuel system supplies too much or too little fuel to the mix Impurity (water) in the fuel ENGINE BASICS (11)

What Can Go Wrong? –Lack of compression Your piston rings are worn (A/F leak) Intake or exhaust valves leak Hole in the cylinder (gasket leaks) –Lack of spark (nonexistent or weak) Spark plug or the wire leading to it is worn out Ignition system not working properly Ignition timing is off or bad ENGINE BASICS (12)

What Can Go Wrong? –Others…. Battery dead (engine not turning) Crankshaft bearing jammed Valves do not open at right time or at all Exhaust pipe blocked Engine seized (no oil) ENGINE BASICS (13)

ENGINE BASICS (14) Overhead camshaft (OHC) –Engines having camshaft mounted above Overhead valve (OHV) –Valves are mounted in the cylinder head above the combustion chamber (opened and closed by push rods) Multi-valve engines –Engines having more than one exhaust or intake valve per cylinder Timing –Delivery of ignition spark, or opening/ closing of engine valves, depending on the piston's position, for the power stroke (timing chain or timing belt)

ENGINE BASICS (15)

OTHERS (1)

OTHERS (2) Producing More Power –Increase displacement –Increase the compression ratio (requires higher-octane gasoline) –Use turbochargers and superchargers pressurize the incoming air to effectively cram more air into a cylinder –Use intercooler –Put more intake valves (polished intake manifold, bigger air filters) –Put more exhaust valves (dual exhaust pipes, free-flow manifold) –Everything lighter! –Inject fuel

THE END IQ + EQ + SQ = TQ*