Transcript CCAS 3381 AUTOMOTIVE SKILL I

CCAS 3381
AUTOMOTIVE SKILL I
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)
Rotary engine
(Mazda R7)
Combustion is
key!!!
ENGINE BASICS (3)

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 (4)
ENGINE BASICS (5)

Core of engine is cylinder - piston
moving up and down inside the cylinder
(one cylinder)
V
Inline
Engine configurations
Boxer
ENGINE BASICS (6)
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 (7)
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 (8)
DISPLACEMENT
VOLUME
ENGINE BASICS (9)
CLEARANCE
VOLUME
TDC
BDC
ENGINE BASICS (10)
Engine Control Unit
ENGINE BASICS (11)

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 (12)

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 (13)

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 (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*