Selecting boost table based on used gear
The first two parameters in the Boost setup menu determine which of the three available
Boost setpoint tables the SM4 will select, based on which gear we are on.
The Boost setpoint tables are where one selects the wanted boost pressure.
Parameter Boost setpoint 1-2 determines which gear ratio, (Kph/Krpm) that will select the
Boost setpoint 2 table instead of the Boost setpoint 1 table.
The gear ratio is in units of kilometers per hour times 1000 divided by the engine speed in rpm.
If the gear ratio is above the value set in parameter Boost setpoint 1-2, then Boost setpoint 2
table will be used.
For this to work, it is essential that there is a Vehicle speed signal connected to the SM4, and
that Speed setup is properly configured. See chapter about Speed setup for more information.
If we want to use the Boost setpoint 1 table on first gear, and the Boost setpoint 2 table on
gears 2 and up, then set parameter Boost setpoint 1-2 to a value in between the gear ratios of
first and second gear.
Example:
Lets say that the gear ratio on first gear is 8.78 Kph/Krpm, and the gear ratio on second
gear is 14.79 Kph/Krpm. (8.78 + 14.79) / 2 = 11.785 Kph/Krpm. Setting parameter Boost
setpoint 1-2 to the value 11.79 will make it so that the Boost setpoint 1 table is used on
first gear, and that the Boost setpoint 2 table will be used on second gear and higher.
Parameter Boost setpoint 2-3 determines which gear ratio that will select the Boost setpoint
3 table instead of any of the tables Boost setpoint 1 and Boost setpoint 2 in the same way
that the parameter Boost setpoint 1-2 works.
Selecting the Boost setpoint 3 table has priority over the other two tables. So when the Boost
setpoint 3 table is selected, the parameter Boost setpoint 1-2 is overridden. This is true for
both the ways to select Boost setpoint table. Either with the Boost setpoint parameters or
with external switches.
Lets say we don’t want the boost table to be selected based on choosen gear. Then we simply
disable it by setting both the parameters Boost setpoint 1-2 and Boost setpoint 2-3 to a very
high value that will never be reached. For example 300 Kph/Krpm.
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