KMS MP25 - Page 36

KMS MP25(M)/MA25(M) manual Version 4.2
36
3.2.4.1.10.1 Parameters Boost Control
Solenoid frequency:
Each control valve has a specific frequency at which it operates best. This frequency can be entered
here between 16 and 40 Hz.
Sample rate:
Specifies the number of measurements per second for detecting boost pressure. In case of control
instability, you need to input a lower value. If the control system responds too slowly, a higher
value has to be entered.
Max PWM:
A linear solenoid valve will only open at a certain pulse width and reach a maximum opening at a
pulse width less than 100%. Here you need to enter the pulse width (as a percentage) above which
the solenoid valve will open completely.
Min PWM:
Here you need to enter the pulse width (as a percentage) beneath which the solenoid valve will
close completely.
Start RPM:
Here you can enter the rpm at which the control may activate. This helps avoid unnecessary
operation of the solenoid valve at low revs.
Boost Limit (ignition cut off):
In case the boost pressure exceeds the target value (risk of engine damage), you can specify a limit
with this parameter. When the boost pressure reaches this limit, ignition and injection will be
interrupted.
Setup pressure:
To allow the turbo system to respond as quickly as possible but not overshooting the target, it is
important that the PID control only activates above a certain boost pressure (the boost pressure
should reach first a stable pressure with the fixed PWM value). Therefore the setup pressure (in
kPa) should be kept slightly lower than the target boost pressure (recommended: 20 – 40 kPa below
target pressure). From this setup pressure the PID starts to control the boost up to the target.
So it is important that boost pressure will reach setup pressure with the fixed PWM values,
otherwise PID control wil not activate!
Setup hysteresis:
Once the setup target pressure has been reached and the pressure consequently decreases, it is
advisable not to switch off the control at once, but to allow for a certain pressure reduction prior to
switching off.
Correction amplifier:
For input of the control amplifier gain. With a gain factor the first step will be larger to reach the
target boost value faster.
Overshoot reduction:
Under certain conditions the boost pressure can exceed the set target pressure faster than normal.
With this parameter you can enter the maximum boost pressure increase (in kPa) between 2
samples, before the turbo control intervenes to reduce turbocharging pressure.