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boostcontrol [2010/07/29 11:05]
twdorris created
boostcontrol [2024/03/15 11:16] (current)
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 ====== ECU-based Boost Control ====== ====== ECU-based Boost Control ======
 +ECMLink'​s boost control functions are modeled after the factory implementation provided by Mitsubishi on 1995+ DSMs and Lancer EVOs.  The idea is to start with a base duty cycle curve that fairly closely produces the desired boost and then let the ECU do some minor error correction to keep things in line.
  
 +The idea is **not** to just dial in a desired boost and let the ECU try to achieve it for you.  You won't be happy with the results. ​ Your boost pressure will either spike too high or take too long to build or oscillate too much.
 +
 +Instead, you want to start with a good base duty cycle table and then let the ECU fine tune from there.
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 +
 +===== Main sections =====
 +
 +To keep this page more "​readable",​ we're going to split the following sections out.
 +
 +  * [[bcsoverview|Operational overview]]
 +  * [[bcschoice|Which solenoid to use]]
 +  * [[bcsinstall|Installation,​ including hose configurations and wiring]]
 +  * [[bcssetup|Dial-in and setup]]
 +
 +
 +
 +===== Logging support =====
 +There are several log values available for working with the Boost tab.  These include the following.
 +
 +  * **WGSBoostTarget** - The current value the ECU is using from the Boost Target table.  This is what the ECU considers its current boost target value used to drive error correction (when enabled).
 +  * **WGSGear** - The gear the ECU is using for both the Boost Target Target and Base Duty Cycle tables.  This is just a sanity check so you can see for sure which gear the ECU believes you're in.
 +  * **WGSDuty** - The current WGS duty cycle used by the ECU.  This is the final duty cycle, which will include any active error correction (WGSTrim).
 +  * **WGSTrim** - The current amount of error correction applied on top of the base duty cycle.
 +  * **ECUBoost** - The ECU's idea of boost based on the configuration entered into the ECU-side of the ECU Inputs tab.
 +
 +===== Technical details =====
 +The ECU's WGS output is fixed at 17hz (period of 0.06 seconds).
 +
 +A "duty cycle" here refers to how much of each 0.06-second period is considered "​active"​ versus "​deactive"​.  A duty cycle (DC) of 100%, for example, just means the output is always active (tied to ground).  Likewise, a DC of 0% just means it's always deactive (the output is floating).
 +
 +Values between these two extremes indicate how long the output is held active before being deactivated during each 0.06-second interval.  A DC of 75%, for example, means the output will be tied to ground (active) for 0.75 * 0.06 = 0.045 seconds and then switched off (deactive) for the remaining 0.015 seconds, then switched on again for 0.045 seconds and switched off again for 0.015 seconds, etc.
 +
 +This provides a relatively smooth analog approximation to a variable value using an on-off solenoid and a digital output from the ECU.  Digital outputs and simple solenoid air valves are much less expensive than analog alternatives and provide reasonable approximations.
  
boostcontrol.1280415925.txt.gz · Last modified: 2010/07/29 11:05 by twdorris