POWER
stroke:
this
is
the
start
of
the
second
revolution
of
the
engine.
While
the
piston
is
close
to
Top
Dead
Center,
the
compressed
air–fuel
mixture
in
a
gasoline
engine
is
ignited,
usually
by
a
spark
plug,
or
fuel
is
injected
into
the
diesel
engine,
which
ignites
due
to
the
heat
generated
in
the
air
during
the
compression
stroke.
The
resulting
massive
pressure
from
the
combustion
of
the
compressed
fuel
‐
air
mixture
forces
the
piston
back
down
toward
bottom
dead
center.
Detail
Piston
moves
from
TDC
to
BDC
Intake
valve
closed
Exhaust
valve
closed
Rapid
burning
causes
rapid
rise
in
temperature.
Rapid
rise
in
temperature
causes
increased
pressure.
Pressure
induces
a
force
on
the
piston.
Force
on
piston
produces
torque
on
crankshaft.
540
degrees
rotation
EXHAUST
stroke:
during
the
exhaust
stroke,
the
piston
once
again
returns
to
top
dead
center
while
the
exhaust
valve
is
open.
This
action
evacuates
the
burnt
products
of
combustion
from
the
cylinder
by
expelling
the
spent
fuel
‐
air
mixture
out
through
the
exhaust
valve(s).
Detail
Piston
moving
from
BDC
to
TDC.
Intake
valve
closed
Exhaust
valve
open
Waste
gasses
are
expelled
from
the
cylinder.
720
degrees
of
rotation