SS swap into 95 Impreza LX

[BoostedSubie]

Yes, that is what I was refering to except on the Impreza ecu not the Legacy ecu. The atmospheric pressure sensor is not the Pressure sensor though. Subaru calls their MAP sensors pressure sensor refering to the Manifold pressure. The atmospheric is different and the Pressure sources switching solenoid swaps between the manifold pressure and atmospheric pressure i believe, also called the pressure exchange solenoid.

[Legacy777]

Yes, on the second gen Impreza and I think the Legacies they have a pressure sensor that reads manifold vacuum and uses the pressure exchange solenoid to switch to read atmospheric pressure every now and then.

[BoostedSubie]

So, wtdash, I believe you were right as the atmospheric pressure sensor being the map sensor. I've been doing more digging and found more diagrams. I was looking at a wiring schematic that showed the "Boost Sensor" being only on the automatic models and shows the signal wire going to pin 23 at the ecu. Well, pin 23 on the ecu pinout is the atmospheric pressure sensor. Why they call it the atmospheric pressure sensor on the pinout but the Boost sensor on another diagram is a bit confusing as it is not reading atmospheric pressure, its reading manifold pressure.

[Legacy777]

As I mentioned above, the sensor reads both atmospheric pressure and manifold pressure. There is a switching solenoid that does this.

[BoostedSubie]

Oh Ok, I was under the assumption that there was a map sensor, an atmospheric sensor, and that the pressure exchange solenoid switched between the two. Makes more sense now, thanks.

[BoostedSubie]

So, Its been a bit since I've been able to work on my car due to lots of overtime at work. I'm done with all the wiring for the most part besides the self shutoff control. I had an old Legacy harness lying around so I stripped it and found the MPFI diode for the self shutoff control, now I understand what it all does. Looking at the top of it, it is 2 pieces, there are four wires going into it, the light green and yellow wire into one half, red/black and white/red into the other half. Both halves are labeled with a 1.5a. I know the light green y's off to the ecu self shutoff pin and the main relay, but where do the other wires go? I assume the yellow goes to a power but not sure whether its switched or not. Is the other half of this a diode for something else or are they both for the self shutoff?

[BoostedSubie]

Here is the diode


The jumper harness I made, it wasn't finished when I took this so it looks a little messy

[Legacy777]

I'm not so sure that's the correct diode. However, that doesn't mean it shouldn't work. It appears that there are actually two diodes in that harness/connector.

The diagram below shows how the diode should be wired up. You would only want to use one of those diodes. You'll need to use a multimeter or get creative to check which end of the diode is which.

http://www.surrealmirage.com/subaru/fil ... rical1.jpg

[BoostedSubie]

I figured it was two different diodes, I just wondered since I saw a thread on here where n2x4 did a similar swap and used a diode from radio shack and he used a 3a, the factory one I found is 1.5a. It should be the right diode, I had the harness stripped down bare and traced the light green wire to the self shutoff pin and the main relay. Also in the diagram you posted it shows the wire colors to be correct. Thanks for the diagram, that should settle it.

[BoostedSubie]

The green wire should be for the cathode and the yellow is the anode. I also found in n2x4s thread that the yellow (anode) should be hooked up to a switched 12v source courtesy of Vikash.

[Legacy777]

Thanks for following up and for the info.

[BoostedSubie]

Yep, now hopefully I can get the rest of the wiring done this weekend and get it started. I still have plenty left to do. Interior, FMIC piping, body work and paint. I'm going to take some more pics this weekend and want to start a build journal.

[BoostedSubie]

I didn't like the mess of the jumper harness, so I ended up labeling all the harness wires at the ecu plug then cut the plug off. Then I soldered the Legacy ecu plugs to each corresponding wire. I'm pretty much done with it except a couple wires that I have questions about. For one, on the Impreza harness, the cam and crank angle sensors use the same shield at the ecu, I'm sure further down the harness, it splits off. I'm wondering if it is going to be ok to join the crank and cam shield wires from the Legacy plugs to the one shield of the Impreza harness. Another thing is the O2 sensor wiring. The Impreza harness has a O2 signal, O2 heater ground, O2 heater signal, and O2 shield. So what is the heater signal? Is it just power for the O2 heater. It uses a 3 wire 02 stock just as the Legacys use, so if the 02 heater signal is really just the power for it, can I just wire it into a 12v power source? One more thing, some of the Impreza sensors such as the MAF get its power from the same supply as the Injectors so will the Legacy ecu be effected by not sending the MAF its power? I just want to make sure on some of this stuff so if I do have problems getting it running, I'm not chasing 100 leads trying to figure out whats wrong. Any info/advice is greatly appreciated.

[Legacy777]

On the O2 sensor, I would assume the heater signal is just a 12v supply. If you're running the turbo legacy ECU then you could probably just hook that up to match the turbo legacy setup.

It "should" be ok with getting the 12v power how it's setup now. I don't see any reason why it wouldn't work, but I can't say exactly how the ECU is programmed and if it'll be cranky about it.

[BoostedSubie]

Link to my build
http://bbs.legacycentral.org/viewtopic.php?f=25&t=52127