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The following Subaru models are applicable to this document:
2022+ Subaru WRX 6MT
Table Descriptions
Besides this document, an additional resource for ECU logic details are the table descriptions shown in the Accesstuner software. These will show up in the lower left corner of the software for the current table that is selected. If not visible, make sure the "Table Description" check box is selected in the View menu. Additionally, the Help menu in the software contains links to documents that list all of these table descriptions as well as all of the data monitor descriptions.
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ECU Changes
When compared to other FA engine DIT vehicles here are some of the notable differences in operation you can expect:
Limits
Boost Reading (Map MAP Sensor Values)
Currently limited to a max of about 61.5 psig at sea level, not including the hardware limit for the factory MAP sensor (which likely is limited to about 24 psig at sea level). We have included the MAP calibration tables to account for the installation of an aftermarket MAP sensor. Keep in mind if you choose to replace it that , the factory MAP sensor includes an IAT sensor to read air temperature in the manifold.
Boost Target
Boost targets can go to a maximum of ~61.5 psig as at sea level when the Boost Targets Max. Limit table is raised from its 24 psi limit.
Load Limit
Limited to just under 4.0 g/rev.
Injector Pulse Width (IPW)
At higher load with richer fuel targets it’s entirely possible to hit , a hard-coded limit for IPW. This IPW limit can be hit that will cause the IPW to go static in the 7.x ms range which can cause and the car to run a different target than intended ( leaner than expected). This is the same limit that was present in prior DIT that was addressed via the CCF Gen 2 features on the 15-21 WRX. The feature to expand the IPW limit has not yet been added to the 2.4L WRX ECU.
Requested Torque
Internal values in the ECU cap the requested torque value at 350 N-m.
Throttle
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Mapping
The 2.4L WRX has some unique changes related to requested torque:
Requested Torque
Tables are split by the estimated (calculated) gear position (1st through 6th). This ecu utilises ECU utilizes a new monitor (Gear Position ESTIMATED Req Torque)which tracks the unique gear position monitor and is used for table switching.
Due to internal ECU limits, the maximum Requested Torque value is capped at 350 N-m.
Requested Torque (Gear Transition)
This table is used when the car is transitioning between gears.
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During testing, we observed that certain 2022 WRX vehicles can demonstrate very significant knock corrections under very “light duty” conditions. We were able to identify a few conditions that can cause this to occur.This typically occurs when:
The driver reduces throttle input after an acceleration event, but does not lift off of the accelerator entirely, such as when reaching desired speed after leaving a stop light or entering the freeway.
Engine Speed is between 2000 and 3000 RPM.
Calculated Load is below 0.5 g/rev.
Some symptoms of When this behavior can bebegins:
Feedback Knock Correction (FBKC) can rapidly increment negative into large absolute values
It will often continue until the driver inputs change, such as increasing or decreasing accelerator position, or until the FBKC value reaches the maximum negative value allowed by the calibration.
If you keep an eye on the monitor Knock Sensor Noise Level Cylinder 3 monitor, you will typically see large spikes in the value.
If you compare these spikes against the Knock Sensor Level Threshold Cylinder 3 monitor, you’ll be able to see that any time the noise level exceeds the threshold, there will be an increment in the FBKC
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.
Our testing indicated that:
The behavior is not consistent across cars but will be easily observed on the stock (or Stage0) calibration
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for those cars that are most heavily impacted.
This issue is not specifically worsened or alleviated by changes in octane; it was observed on 91 octane fuel up to 96 octane fuel.
It is unlikely that the noise is being generated by legitimate knock events and that it is mechanical/external noise (or
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another anomaly).
Many
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FA24 vehicles
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, including Ascent, also
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exhibit the noise spikes on Cylinder 3, but often to a reduced
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maximum, effectively reducing or entirely negating the severity of the issue
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.
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It’s possible the
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Mitigating the Light Load Knock
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Our Stage1 maps have a series of small changes included that help reduce the frequency of these light load knock events, though larger changes may be needed depending on the vehicle and the specific behaviors observed.
Below you can see a Visual visual representation of the issue occurring on an in-house test vehicle during early R&D efforts. This is on the stock calibration and a vehicle running 92 octane located in Portland, OR. The 3rd graph shows the noise spikes (red) exceeding the threshold (white), the 2nd graph shows FBKC incrementing downwards when those spikes occur, and the 1st graph shows the benign conditions under which it is occurring (Calculated Load below 0.5 g/rev, APP below 15%, etc.). While not shown in this graph, Cylinders 1, 2 and 4 do not demonstrate the noise spikes at all during this event.
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