Subaru EJ 2.0L (02-05 WRX MT) CCF Additions


Subaru EJ 2.0L V3.0 CCF Additions

Version 1.0



The factory EJ 2.0L ECU has a number of limitations when attempting to tune higher power cars. COBB implemented a series of changes to facilitate tuning these cars with the introduction of the "SD" ECU type - later renamed to the COBB Custom Features (or CCF) ECU type. As always, our engineers have made things as seamless as possible, but due to the extensive changes necessary to achieve these goals, we've produced this guide to help understand how these features work and what they can do for you.

Speed Density

A powerful yet easy-to-use Speed Density (SD) feature that can be used to entirely replace or work in conjunction with the existing factory mass airflow (MAF) sensor. It is highly customizable and features such as real-time tuning aid in a speedy and efficient tuning process. See our Subaru Speed Density Guide: 2.0, 2.5L, DIT for details.

Load and Airflow Limit Increase

Load and airflow limits inherent to the factory 2.0L ECU have been significantly raised. No longer is there a need to trick the ECU by manipulating airflow/load references and the fuel injector scale in order to overcome the limits in the tune. Simply tune with actual real-world values up to 10.0 g/rev of load and up to 655 g/s of airflow in any table. Additionally, the SD-based load value is directly calculated and is subject only to the 10.0 g/rev load limit (regardless of airflow).

Boost Target Limit Increase

The factory EJ 2.0L ECU has an inherent maximum limit in the Boost Targets table of 24.75 psi (relative at sea level). That is, even though the factory 2.0L ECU can monitor and target effectively any level of boost (given a MAP sensor with the appropriate range and calibration), the boost targets table is still limited to a max of 24.75 psi. The COBB CCF ECU raises this limit to 49 psi (relative at sea level). To use, simply enter any boost target value up to 49 psi in the Boost Targets table. Even higher levels of target boost can achieved following the methods outlined here: Tech Bulletin - Targeting High Boost Levels

Per Gear Boost Targets and Wastegate

Real-time tuneable boost targets and wastegate compensations allow boost and wastegate tuning by gear. See our Subaru Per Gear Boost Compensation guide for details.

Other Miscellaneous Features

Gear Position Determination Expanded to Cover 6-Speed Transmissions and New Gear Speed Monitor

The factory ECU estimates the current manual transmission gear position based on vehicle speed, RPM and the thresholds dictated by the Gear Determination Min/Max... table (found in the "Miscellaneous Tables" group). As long as the clutch is out and the vehicle is moving, the ECU will be able to reasonably estimate the current gear. However, the factory 2.0L ECU is only set up to handle 5 gears. For the COBB CCF ECU, this has been modified to be able to handle 6 gears for possible 6-speed transmission swaps. This swap (or any transmission gear ratio change) requires that the Gear Determination Min/Max... table be tuned appropriately so that the correct gear can be estimated. For the COBB CCF ECU, we have simplified this process with the addition of a Gear Speed monitor. This will allow you to view/log the currently calculated rev/mile value that the ECU uses to compare to the Gear Determination Min/Max... table thresholds to estimate the current gear. This table's thresholds are set up as follows:
1st gear estimated if gear speed is greater than or equal to table value #1
2nd gear estimated if gear speed is less than table value #1 and greater than or equal to table value #2
3rd gear estimated if gear speed is less than table value #2 and greater than or equal to table value #3
4th gear estimated if gear speed is less than table value #3 and greater than or equal to table value #4
5th gear estimated if gear speed is less than table value #4 and greater than or equal to table value #5
6th gear estimated if gear speed is less than table value #5

The gear speed value will tend to vary a bit within a certain range for the current gear. As such, you will want to set up the thresholds in the Gear Determination table so that the average gear speed value you see when logging for a given gear will be a midpoint between the appropriate two thresholds in the table. For example, if 1st gear shows a logged gear speed value hovering around 10,000 and 2nd gear shows a logged value around 8,000, then 9,000 would be reasonable for the first value in the table. This would avoid the incorrect gear being estimated due to noise in the gear speed value. For example, if you set table value #1 too close to the observed gear speed of 2nd (say 8,200 in the example above), then the ECU would sometimes determine you were in 1st gear when you were actually in 2nd.

When doing a transmission swap from an EJ 2.5L car, you may decide to copy the values from that ECU's Gear Determination table into your CCF tune. While this is a good starting point, we have found that further tweaking of the table may be necessary to avoid incorrect gear estimation. Always verify your table threshold values by logging the gear speed monitor for each gear (across a broad RPM range where possible). When you have finished tweaking the table, verify that the Gear Position monitor shows the correct estimated gear (with clutch out and vehicle moving) for every forward gear in the transmission (also across a broad RPM range where possible). Note: A value of "7" will be shown for gear position when the transmission is in neutral (this is different than the MAF ECU which will show a value of "0" in this case).

Injector Latency Adder

A real-time tunable table named Fuel Injector Latency Adder (Small IPW) (found in the "Fuel Tables" > "Injectors" group) has been added to the COBB CCF ECU. This is an adder to the current injector latency based on the current injector pulse width. This can be useful to tune for the non-linearity of larger injectors at low injector pulse widths to improve idle/low load behavior.

Neutral Position Switch Invert

Some manual transmission swaps require that the neutral position switch determination by the ECU be inverted. The COBB CCF ECU allows you to do this via the Neutral Position Switch Invert (MT) toggle in the "Edit" > "Advanced Parameters" -> "Toggles (Base)" menu. Simply uncheck this toggle, save map, and reflash to car if you wish the neutral position switch to be inverted. To verify operation, live connect to the car with the Accesstuner software and bring up the Neutral Position Switch monitor in the dashboard. This monitor should show "ON" when the transmission is in neutral and "OFF" when the transmission is in gear.

More Flexible MAP Calibration Offset

The factory 2.0L ECU only allows for effectively a negative offset for MAP sensor calibration. This presents a problem when using aftermarket MAP sensors that require a positive offset. The COBB CCF ECU overcomes this issue by allowing either a positive or negative offset to be entered. This gives you the ability to tune for any aftermarket MAP sensor that is compatible with the car.

Tunable IAT Calibration Axis and Latency Axis

The factory 2.0L ECU does not allow for editing the individual cells that make up the voltage axis of the Intake Temp. Sensor Calibration and the Fuel Injector Latency tables. This prevents you from modifying the intake temp sensor voltage and battery voltage values (respectively) in these tables. The COBB CCF ECU overcomes this limitation and allows you to edit any cell in either of these tables.

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