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Knock
'
threshold
'
Under
certain
condit
ions,
the engine runs as
close
the
efficiency of
fuel
utilization.
ni
ng
conditions.
Methods of preventing
Knock may be prevented
t
o TOC, the pressure and temperature
also p revented by enriching the mixture, which has the effect
• Knock
may
be
caused by the
Use
of a
fuel with
an octane
ratio.
pression ratio. A
lean mixture
-
combustion
resulting in high
temperature
radiator or
thermostat,
-
Incorrect or worn
spark
is incorrectl or is it IS
fouled
timing. The resistance to
w
ill
higher
be
-
A
sudden
increase
in engine speed.
creased.
If the engine is
pression of
the accelerator will produce
time to
adjust
the
timing
the cylinders.
of the
number of
degrees
however,
the
combination
as possible
t
o
the knock
In
other
words.
knock
by
retarding the
ignition. Since
in
the
cylinder
fo llowing
:
rating
is
too
too
mixture
is
lean,the
may be due
a
10
temperature.
Carbon
the risk
or
to rustnime deposits m the
plugs.
The fisk of detonation will be greatly mcreased if the plug IS
.
knock Will be
impaired
under
these conditions.
What
is
known
running under normal
conditions
an
instantaneous increase
accordingly.
For
a brief period,
fun ct
ions
with which
the control unit
per
cran
kshaft
Design and function
of high perlormance and
threshold.
The
closer
the
knock
threshold
is
detonation
are
t
hereby
lowered, reducing the
of reducing
low for
the
compression
temperature
In the combustion
such as tow fuel pressure or air
deposits
in
Ihe
combustion chamber
of
glow
IgnitIon).
DefiCient
cooling
passages). Will have the $time effect.
if
ignition takes
place
as 'transitional"
knock w
of speed and
load
in
the quantity of mixture admitted
therefore.
the timing
is
programmed limits
Group
low
fuel
consumption
the
curve
to the threshold
a
not
fixed limit, but varies depending on
of
the mixtu
re occurs
when the piston
r isk
the
combustion
rat
io
of
Ihe
engine.
chamber
be
h
leaka
ge into
cooling (due,
for
example,
o
f
the wrong type
too
early. since the cylinder
ill
occur if the engine speed
{with the
timing fairly weI!
will be too
advanced
for the amount
the
scope of
timing
28
Igni
rion sysrems
functions
demands
that
,
Ihe
higher
run
is
closer
of
detonation
.
Knock
tem
p
erature.
igh
despite a conslant com·
the
induction system.
the rate
of
heat dissipation,
to
a
water
pump,
if
the
heat
rating
pressure
and tem-
and
load
are
suddenly in·
advanced),
sudden
de-
before the
system
has had
of mixture
adjustment
to
a spec-
29
-
is
in
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