CCAS 3381 CCAS 3381 AUTOMOTIVE SKILL IAUTOMOTIVE SKILL I

INTERNAL

COMBUSTION (IC)

ENGINE

OBJECTIVESOBJECTIVESTo understand the operational

principles and basic mechanisms of the internal combustion engine

Lecture – 1 hourWorkshop – 1 hour

ENGINE BASICS (1)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 ENGINE BASICS (2)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 (3)

ENGINE BASICS (4)ENGINE BASICS (4)

ENGINE BASICS (5)ENGINE BASICS (5)Core of engine is cylinder - piston

moving up and down inside the cylinder (one cylinder)

Inline

V

BoxerEngine 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)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 (7)

ENGINE BASICS (8)ENGINE BASICS (8)

TDC

BDC

CLEARANCEVOLUME

DISPLACEMENTVOLUME ENGINE BASICS (9)ENGINE BASICS (9)

ENGINE BASICS (10)ENGINE BASICS (10)

Engine Control Unit

What Can Go Wrong?–Three fundamentals:

Bad fuel mix Lack of compressionLack of spark

(Beyond these, thousands of minor things can create problems)

–Bad fuel mixNo petrol Air intake clogged (petrol but no air) Fuel system supplies too much or too

little fuel to the mixImpurity (water) in the fuel

ENGINE BASICS (11)ENGINE BASICS (11)

What Can Go Wrong?–Lack of compression

Your piston rings are worn (A/F leak) Intake or exhaust valves leakHole 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 properlyIgnition timing is off or bad

ENGINE BASICS (12)ENGINE BASICS (12)

What Can Go Wrong?–Others….

Battery dead (engine not turning) Crankshaft bearing jammedValves do not open at right time or

at allExhaust pipe blockedEngine seized (no oil)

ENGINE BASICS (13)ENGINE BASICS (13)

ENGINE BASICS (14)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 cylinderTiming – 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)ENGINE BASICS (15)

OTHERS (1)OTHERS (1)

OTHERS (2)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 ENDTHE ENDIQ + EQ + SQ = TQ*