From
http://www.vems.hu/wiki/index.php?page=MembersPage%2FPhatBob%2FUserGuideUnder the section Configuring Air Metering.
Speed Density (MAP vs RPM)For turbocharged and Normally Aspirated (NA) plenum based engines with mild camshaft timing, Speed Density provides the best metering solution.
ConfigurationSet MAP Multiplication to: Enabled
Set max RPM for Alpha-N (rpm) to: 0
Set max RPM for Speed Density (rpm) to: 0
Alpha-N (TPS vs RPM)Best suited to NA engines running independent throttle bodies (ITBs) where MAP readings are noisy and lack resolution.
ConfigurationSet MAP Multiplication to: Disabled
Set max RPM for Alpha-N (rpm) to: 25500
Set max RPM for Speed Density (rpm) to: 25500
Alpha-N with Map multiplicationTurbocharged engines running ITBs are a special case, they have the same problems with MAP noise and resolution when off-boost, but need the MAP to be factored in at anything over atmospheric pressure.
ConfigurationSet MAP Multiplication to: Enabled
Set max RPM for Alpha-N (rpm) to: At least 500 to 1000RPM below the max RPM for Speed Density (rpm)
Set max RPM for Speed Density (rpm) to: The RPM below where the Turbo starts to provide positive pressure.
Alpha-N/Speed Density blendingFor NA engines with plenums that use more extreme camshafts and as a result have very noisy MAP signal at lower RPMS due to the valve overlap. Configuration values are dependent on the characteristics of the engine.
ConfigurationSet MAP Multiplication to: Enabled
Set max RPM for Alpha-N (rpm) to the RPM point just above where the MAP signal starts to read cleanly.
Set max RPM for Speed Density (rpm) to a value just below the Alpha-N value.
Mass Air Flow (MAF)In cases where a Mass Airflow Sensor is used to provide a Load value.
ConfigurationSet MAP Multiplication to: Disabled
Set max RPM for Alpha-N (rpm) to: 0
Set max RPM for Speed Density (rpm) to: 0