When someone says "my car isn't making boost," the very first thing that I want to know is the value of the DAM parameter stored in their car's ECU.
DAM is an acronym for Dynamic Advance Multiplier (also called IAM or Ignition Advance Multiplier in RomRaider and ECUFlash definitions). This value will vary between 0.0 and 1.0 on 32 Bit Subaru ECUs and between 0 and 16 for 16 Bit Subaru ECUs.
A normal and healthy engine running normal and healthy fuel should have a DAM that is 1.0 for 32 Bit ECUs and 16 for 16 Bit ECUs. An exception to this is immediately after the ECU is reset, the DAM will be set LOWER THAN the maximum value (0.5 OR 12) for the OEM map and allowed to increment when the car is driven.
So what is DAM and why do I ask you to post its value? First of all, I'll tell you what DAM isn't -- DAM is NOT an indication that something is catastrophically wrong with the engine and neither does it tell us exactly what is going on, but it's a tool in our arsenal to rule out some things while focusing effort on checking other parameters. DAM is a component within Subaru's knock control strategy that allows GLOBAL timing adjustments based on a table called Knock Correction Advance (or KCA). When the DAM value is decremented, this is allowing the ECU to retard the timing over a wide range of RPM and Load cells. The primary purpose of the DAM strategy is to address Fuel Octane inconsistencies, but the DAM parameter can also respond to situations where Engine Knock is present throughout the rev band like those caused by vac leaks, boost leaks, fuel system problems, and improper mapping.
![328765]( "328765")
KCA Table Taken from a 2015 STI base map
Subaru's Knock Control strategy is complicated and varies depending on model and year, but one thing is consistent: when the DAM parameter drops sufficiently low, Subaru's ECU logic responds by zeroing out the boost control in an effort to minimize engine damage. On EJ engines, this is done by zeroing out the WGDC table thereby disallowing the ECU to hit its target boost. This doesn't mean that the car will not make boost -- it will, but only up to the physical exhaust pressure required to open the wastegate. On Turbo Subarus, this wastegate pressure allows the car to hit between 6 and 9 PSI of boost, depending on model and ambient conditions.
To find out the value of your DAM, use your AccessPort or OpenPort2.0 and live monitor the value of Dyn. Adv. Mult. (AP) or IAM (OP2.0). You do not need to drive the car or datalog to obtain this value -- this is not a value that is tabled along with vehicle sensors.
![328766]( "328766")
DAM is an acronym for Dynamic Advance Multiplier (also called IAM or Ignition Advance Multiplier in RomRaider and ECUFlash definitions). This value will vary between 0.0 and 1.0 on 32 Bit Subaru ECUs and between 0 and 16 for 16 Bit Subaru ECUs.
A normal and healthy engine running normal and healthy fuel should have a DAM that is 1.0 for 32 Bit ECUs and 16 for 16 Bit ECUs. An exception to this is immediately after the ECU is reset, the DAM will be set LOWER THAN the maximum value (0.5 OR 12) for the OEM map and allowed to increment when the car is driven.
So what is DAM and why do I ask you to post its value? First of all, I'll tell you what DAM isn't -- DAM is NOT an indication that something is catastrophically wrong with the engine and neither does it tell us exactly what is going on, but it's a tool in our arsenal to rule out some things while focusing effort on checking other parameters. DAM is a component within Subaru's knock control strategy that allows GLOBAL timing adjustments based on a table called Knock Correction Advance (or KCA). When the DAM value is decremented, this is allowing the ECU to retard the timing over a wide range of RPM and Load cells. The primary purpose of the DAM strategy is to address Fuel Octane inconsistencies, but the DAM parameter can also respond to situations where Engine Knock is present throughout the rev band like those caused by vac leaks, boost leaks, fuel system problems, and improper mapping.
KCA Table Taken from a 2015 STI base map
Subaru's Knock Control strategy is complicated and varies depending on model and year, but one thing is consistent: when the DAM parameter drops sufficiently low, Subaru's ECU logic responds by zeroing out the boost control in an effort to minimize engine damage. On EJ engines, this is done by zeroing out the WGDC table thereby disallowing the ECU to hit its target boost. This doesn't mean that the car will not make boost -- it will, but only up to the physical exhaust pressure required to open the wastegate. On Turbo Subarus, this wastegate pressure allows the car to hit between 6 and 9 PSI of boost, depending on model and ambient conditions.
To find out the value of your DAM, use your AccessPort or OpenPort2.0 and live monitor the value of Dyn. Adv. Mult. (AP) or IAM (OP2.0). You do not need to drive the car or datalog to obtain this value -- this is not a value that is tabled along with vehicle sensors.
