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2002 Base Forester 5MT
36 Posts
Discussion Starter #1
Hey all, as the design stage of my suspension setup is coming to a close and fabrication is coming nearer, it's time for me to think about engines and management:

TLDR; I think I'm going to swap the EZ30 engine into my SF. While there are plenty of swaps done that involve splicing the ECU/TCU from an Outback, I would prefer to just keep the engine management from my SF. I also want to keep it manual, so I would like to avoid the mess of spoofing the TCU.

Yesterday at work I started thinking about how I wanted to go about this, and I have some thoughts, but would like to hear some critical technical feedback, as anything helps!

So the initial plan is this:

The EJ25 is a 4 cyl (of course) but like every engine, has a TDC. At it's roots, firing pattern and ignition pattern are the real two differences between this and a 6 cyl (Yeah it could be argued that there's a ton more that's different, but for matter of argument I'll stick with this).

By intercepting all four ignition and injector sequences, I could essentially interpolate this into a 6 cylinder pattern, no? The EJ fires on 180 degree marks for two cranks, and the EZ fires on 120 degrees sequentially.
At the same RPM:
  • The first cylinder of each firing sequence will trigger at the same time on the first crank cycle
  • The 3rd cylinder of the EJ will fire at the same time as the 4th cylinder in the EZ order (cylinder 2).
This gives us two solid timing marks. The other two EJ marks do not line up with the ignition marks of the EZ motor, however, they can be used for calculating timing for the other 4.

The system could also "sip" off of the cam/crank position sensors for added accuracy, also the TPS.

I'm going to setup a quick bench test between 3-4 "ESP-32's" (high frequency arduinos, small, very fast and fairly stable). The reason I would like 3 or 4 is for data acquisition and redundancy:
  1. Data input, organization
  2. Data collection, sorting
  3. Data interpretation, output
  4. Pre-mapped redundancy map for an emulated "limp mode"
I already have a collection of mosfets that will be able to drive the injectors and ignition signals, I just need voltage dividers to process the signal, then I'm going to emulate the signals with a waveform generator I have. By the time this is done, confirmed, and stable, my suspension will be done and I will have my hands on a EZ30.

Other than the inherent slight timing differences, I don't think there should be many issues.

Again, any technical critique would be appreciated. EE and engine management is not my specialty, so I'm just spitballing here.


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