The
four
-
stroke
internal
combustion
cycle
BEFORE
THE
CYCLE
BEGINS
.
The
cycle
begins
at
top
dead
centre
(
TDC
)
.
Here
the
piston
is
furthest
____________________
from
the
crankshaft
.
There
are
four
strokes
of
the
piston
.
____________________
STROKE
.
The
crankshaft
rotates
.
This
makes
the
piston
move
____________________
the
cylinder
,
away
from
the
valves
.
At
the
same
time
,
the
____________________
above
the
intake
valve
rotates
.
This
makes
the
valve
move
____________________
,
which
opens
the
intake
port
.
As
the
piston
moves
down
,
fuel
is
sucked
into
the
cylinder
through
this
inlet
.
____________________
STROKE
.
As
the
crankshaft
rotates
,
it
makes
the
piston
move
____________________
the
chamber
towards
the
valves
.
Simultaneously
,
the
cam
above
the
____________________
valve
rotates
and
allows
it
to
close
.
Both
valves
are
now
____________________
.
As
the
piston
moves
____________________
towards
the
valves
,
it
compresses
the
fuel
.
____________________
.
Now
the
piston
is
once
again
at
TDC
.
The
compressed
fuel
is
____________________
by
the
____________________
plug
,
and
there
is
a
small
____________________
at
the
top
of
the
cylinder
.
____________________
STROKE
.
Immediately
after
this
,
the
gases
____________________
in
the
cylinder
,
which
pushes
the
piston
____________________
.
This
makes
the
crankshaft
rotate
and
provides
____________________
to
drive
the
wheels
of
the
vehicle
.
____________________
STROKE
.
As
the
crankshaft
rotates
,
it
pushes
the
piston
____________________
the
cylinder
.
At
the
same
time
,
the
cam
above
the
exhaust
valve
pushes
the
valve
____________________
.
This
opens
the
exhaust
port
,
and
the
____________________
gases
are
pushed
out
.
The
cycle
is
repeated
____________________
of
times
per
minute
.
