Mystery ECU pressure sensor...?

[free5ty1e]

Hey hey.

Just got a pair of what are supposed to be N/A ECUs for their connectors and am puzzled upon taking the first one apart:



What the fork is that?? There's a hole on the back of this ECU where this thing is aimed. The entire circuitboard's sole purpose appears to be driving this thing, which I suspect is some sort of pressure sensor.

Did some Legacy ECUs use a board-mounted atmospheric sensor instead of sharing the MAP sensor under the hood? The other N/A ECU I have here does not appear to have this strange piece of aircraft-grade technology.

The sensor itself is a thick film hybrid microcircuit - on the exposed thick film (on the top) I can see laser-trimmed resistors. Highly accurate stuff. Overkill, in fact - which does agree with Subaru's engineering practices.

Anyone know for sure what this is and what it's for?

[vrg3]

Non-turbos up through 92 had that kind of onboard barometric pressure sensor.

[rallysam]

Never seen inside the ECU before. Pretty cool. That's not too complicated - we design stuff more complicated than that all the time. But, it is surprising to see so many surface-mount chips from what's basically an 80's design.

[vrg3]

Well, JECS ECUs like this one are of a newer design than the 80s-ish Hitachi ones. It's more of a 90s design. This same basic ECU was used up through like 96 or something overseas.

[rallysam]

Hey Freestyle -

You're just poaching connectors, right? Mind sending me the circuit board when you're done abusing it?

[free5ty1e]

Thanks - I couldn't imagine what else that thing could have been used for. So pre-facelift N/A ECUs have this onboard sensor? Interesting.

All turbos had the under-hood atmospheric pressure sense, correct?

Rallysam - I am mostly poaching connectors, yes. Not sure if I will end up using or experimenting with any other parts of the ECU, but if I don't you'd be welcome to the internals. It may be a couple months though, because of the move. Right now I'm just planning for the next LegacEBC circuitboard while I've got a little breathing room with my paid work.

[vrg3]

Not just pre-facelifts -- 92 models also.

Yes, all turbos used the pressure exchange solenoid to allow the underhood pressure sensor to measure both manifold pressure and atmospheric pressure.

[free5ty1e]

By the by, there were so many high-quality useful components on the ECU boards, I'm not sure you'd want what's left... we stripped the hell out of them.