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2003 Forester AT
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106 Posts
Discussion Starter · #1 ·
This is a How-To article, but I am unable to post in that section of the forum.

PROBLEM: After installing the 13:1 steering rack from 2015+ STIs into other vehicles (Forester, Legacy, older STIs), there may be unwanted intervention/intrusion by the VDC/TCS systems. There are multiple potential sources of this issue, many of which are mechanical (installation problems etc), which should be corrected first. If all mechanical problems have been addressed, the problem likely relates to data received from the steering angle sensor. The change in steering ratio leads the car to believe the wheels are turned less sharply than they are, which in turn causes miscalculations about whether the car is spinning, skidding, etc


SOLUTION: If the steering angle sensor data is indeed the only issue (no contributing mechanical problem), this can be corrected by scaling the SAS data back to normal. Utilizing an arduino chip, we will intercept the SAS signal (via CANBUS), scale it up by the correct percentage, and then send the corrected signal to the car so the VDC calculations will be accurate again.

Because images in forum posts tend to get lost over the years, attached is an in-depth PDF guide detailing this project. Please see said PDF for the exhaustive list of items and procedures required.

In short, we utilize an Arduino board along with two CANBUS shields. The connection from SAS to the car is severed - the SAS signal is wired to one CANBUS board, and then the up-scaled signal is sent out from the other board to the car. A few modifications are required - the CANBUS shields always communicate on via their own pin 10, so we tweak one CANBUS board to run its pin 10 signal to the 8th pin on the Arduino (to give each board its own "channel" so the signals do not interfere). Also, out of the box, the 2x3 pin ISCP header on the CANBUS shields does not have pins sticking out, so we solder a new header (with protruding pins) in place on the middle board, to continue this connection to the top board.


NOTE: I was intent on creating a plug-n-play harness rather than cutting any of my car's harness. When I was doing this project and how-to article, the only solution I could find was to hack OEM harnesses from a junker. I've talked with Brian at iwireservices.com and they are working on obtaining 4-pin harness connectors to fit the male and female SAS plugs, so I am hopeful some of you will be able to benefit from these.


Related pages:


I hope this helps and want to give a big shout-out out to @Hired-Goon and @skirbykat. Hired-Goon authored the sketch and the original how-to article that was lost from OzFoz. Skirbykat has been a huge help and is currently working on adapting this project using even smaller components.
 

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2003 Forester AT
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106 Posts
Discussion Starter · #3 ·
Yes, it is the same. Their website states:

This system is powered by an Arduino Sketch written by hired-goon from ozfoz forums.
To enquire about purchasing a build for your Subaru, please contact us to discuss your requirements.
Feel free to contact that company to see about purchasing one, however I emailed them and never received any response. I'm guessing there was not a ton of demand and they probably aren't doing that project anymore.




As a side-note update, I see there's now a SAS plug available on iwireservices.com, however I only see one plug whereas you would need both the male and female for this project. I'm betting they could get both sides (or just do like I did and harvest it from a wrecked vehicle if that's possible in your area).
 

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2018 2.5i Premium CVT
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I missed this the first time around. It's gotta be the highest of any high tech solution we've ever seen here!

I have posted a link on the DIY, How-To & TSB's forum. That's an honor here!
 

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2003 Forester AT
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Discussion Starter · #5 ·
I missed this the first time around. It's gotta be the highest of any high tech solution we've ever seen here!

I have posted a link on the DIY, How-To & TSB's forum. That's an honor here!
Awesome! I'm very grateful to the original architects of this project and I'm glad it will be readily accessible here on SF.org. Thanks @bbottomley !
 
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