than to a change in the throttle valve position. The
ignition timing also changes much more quickly.
To keep the ignition point as close as possible to
the knock limit and so optimize the efficiency of the
engine, two KS are installed in the engine, which
pick up the mechanical vibrations of the engine
and convert them into an electrical signal for the
PCM.
TIE42093
1
2
A
B1
2
Description
Item
Normal combustion
A
Knocking combustion
B
Pressure characteristic in cylinder
1
Output signal from KS
2
The term "knocking" is used to describe
combustion processes in which the flame front
propagation speed reaches the speed of sound.
This can happen towards the end of combustion
in particular, when unburnt air/fuel mixture on the
combustion chamber walls self-ignites due to the
increase in pressure following initiation of regular
combustion. The resulting pressure peaks damage
the pistons, cylinder head gasket and cylinder
head.
The cylinder in which combustion knock is
occurring is identified from the camshaft position (CMP sensors) and crankshaft position (CKP
sensor) information.
If the PCM detects combustion knock, the ignition
timing for the cylinder in question is gradually
retarded for a few crankshaft revolutions until
combustion knock stops. After that the ignition point
is slowly returned to the calculated value. This
facilitates individual cylinder ignition, which makes
it possible for the engine to operate at optimum
efficiency at the knock limit.
Engine fueling
Fuel is supplied by a non-return fuel system.
Fuel pressure and fuel delivery rate are regulated
by the PCM with the aid of the FPDM. The fuel
pump is supplied with a cycled voltage by the
FPDM. By cycling the voltage, the fuel pump output
can be steplessly adjusted. The fuel pressure can
be steplessly regulated between 3 and 5 bar.
Adjusting the fuel pump output has the following
advantages:
• The fuel pump's power consumption is reduced,
thereby reducing the load on the vehicle's power
supply system.
• The fuel pump's service life is increased.
• Fuel pump noise is reduced.
Fuel pressure regulator
The PCM calculates the required fuel pressure
based on the operating conditions. The PCM
transmits a corresponding PWM signal to the
FPDM. With the aid of this signal, the FPDM
actuates the pump by sending, in turn, a PWM
signal to the ground connection of the fuel pump.
The fuel pump can be steplessly regulated by
varying the pulse width of the PWM signal.
The PCM continuously monitors the fuel pressure
in the fuel rail by means of the fuel temperature/fuel
pressure sensor. If the pressure deviates from the
calculated value, the PCM adapts the PWM signal
to the FPDM accordingly. Thus the fuel pressure
levels out at approx. 4 bar.
For safety reasons, the PCM switches off fuel
delivery if the SRS (supplemental restraint system)
module detects a crash.
Regulation of injected fuel quantity
The electromagnetically controlled injectors dose
and atomize the fuel. The quantity of injected fuel
is regulated by the duration of actuation of the fuel
injectors. The fuel injectors are either closed (not
G1021908en2008.50 Kuga8/2011
303-14- 20
Electronic Engine Controls— 2.5L Duratec (147kW/200PS) - VI5303-14-
20
DESCRIPTION AND OPERATION
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FORD KUGA 2011.0MY WORKSHOP REPAIR MANUAL
