SSANGYONG KYRON 2010.01 Manual page 127

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7) Accelerometer Strategy
▶ Resetting the pilot injection
The accelerometer is used to reset the pilot injection flow in closed loop for each injector. This
method allows the correction of any injector deviations over a period of time. The principle of
use of the accelerometer is based on the detection of the combustion noises.
The sensor is positioned in such a way as to receive the maximum signal for all the cylinders.
The raw signals from the accelerometer are processed to obtain a variable which quantifies the
intensity of the combustion. This variable, known as the ratio, consists of the ratio between the
intensity of the background noise and the combustion noise.
- A first window is used to establish the background noise level of the accelerometer
signal for each cylinder. This window must therefore be positioned at a moment when
there cannot be any combustion.
- The second window is used to measure the intensity of the pilot combustion. Its position
is such that only the combustion noises produced by the pilot injection are measured . It
is therefore placed just before the main injection.
The accelerometer does not allow any evaluation of the quantity injected. However, the pulse
value will be measured when the injector starts injection and this pulse value is called the MDP
(Minimum Drive Pulse). On the basis of this information, it is possible to efficiently correct the
pilot flows. The pilot injection resetting principle therefore consists of determining the MDP, in
other words the pulse corresponding to the start of the increase in value of the ratio (increase of
vibration due to fuel combustion).
This is done periodically under certain operating conditions. When the resetting is finished, the
new minimum pulse value replaces the value obtained during the previous resetting. The first
MDP value is provided by the C2I. Each resetting then allows the closed loop of the MDP to be
updated according to the deviation of the injector.
ENGINE CONTROL SYSTEM
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