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Old 10-01-2007, 07:58 PM   #1
Scooby Specialist
Member#: 61966
Join Date: May 2004
Chapter/Region: RMIC
Location: Denver, CO
2015 WRX & 2013 WRX
Sold: 04 WRX & 06 STI

Default What kind of boost control solenoid/boost controller is this?

Alright, as I recently posted, I bought a used 2006 STI not too long ago, and as of right now, I can't seem to identify what kind of boost controller/boost control solenoid is on the car. Here's a couple quick pics of it:

Notice there's a little screw thing on the back of it (lower left side of the picture), that has a piece of sponge or something over it, which is the only reason I believe it might be a MBC as opposed to an EBC, but there's also a blue connector on the front of it, check it out:

Here's a pic of the other side of it, notice there's a blue connector in it with 2 wires running from it, those wires are tapped/soldered into the 2 wires that go to the factory blue connector that usually goes to the stock boost control solenoid, check it out:

The factory connector for the boost control solenoid is not connected, it was just taped up under the hood, with those 2 previously mentioned wires running from it, take a look:

Also notice the factory boost control solenoid was completely missing from where it's supposed to be:

Now by the turbo, there is no longer a "T", instead one of the vacuum hoses coming from the compressor housing is routed to the "new boost control solenoid/controller" and the vacuum hose coming off the other side of the boost controller is going to the wastegate actuator. I pulled off the hose going to the compressor housing, to check it, and sure enough, the little brass restrictor pill is no longer inside.

Now what I'm really wondering is, is this a MBC or an EBC? I would think with the little screw like thing on the back of it, it's a MBC, but then I have to wonder, why the hell is that blue connector tapped into the wires from the factory connector, and why is that connector on the "new boost control solenoid"? Is it to control boost via the stock ECU, or is it just there to suppress a CEL or something to that effect?

Currently, the car has a DEFI boost gauge & what looks like a D-link controller (so I can play back boost on previous runs), but there's nowhere to adjust the gains or anything, so I'm pretty sure you can't play with the boost from it, check it out:

Now the boost gauge itself is reading right around stock boost levels, so I can't really figure out why someone would want this controller on there, unless maybe he was just trying to get the car to hold more boost in the upper RPM's?!? I know some of the EVO guys do that, but is it really common on STI's? I can't track down a wire from the boost controller going inside the cabin, so if it is in fact an EBC, it would have to be controlled by the ECU.

I pulled up the carpet, and metal covering to check the ECU, sure enough, no signs of splicing/tapping ect, the ECU looked stock. So now I'm thinking, maybe there's an ECUtek/AP/Open-source reflash in the ECU, if that was in fact an EBC, but I can't tell for sure. Like I said though, it's right around where it should be, factory boost wise, so if it has been flashed, I don't know why they wouldn't have raised the boost?!?

Has anyone seen anything like this before? If so, please help as it's driving me nuts not knowing what's on my car!! I've already bought a factory boost control solenoid, just waiting on the little brass pill to come in from my local Subie dealer before I put it back on. In the meantime, anyone have any ideas? Thanks in advance

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Old 10-01-2007, 08:09 PM   #2
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Join Date: May 2004
Chapter/Region: RMIC
Location: Denver, CO
2015 WRX & 2013 WRX
Sold: 04 WRX & 06 STI


Could this be it?

^^^I'm referring to the GM boost control solenoid... is that about what it looks like? That looks pretty familiar...
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Old 10-01-2007, 10:10 PM   #3
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2003 WRX
NF Performance


that's the gm boost solenoid
you sure the car wasn't tuned for it?
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Old 10-01-2007, 10:24 PM   #4
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Chapter/Region: VIC
Location: vancouver B.C
2011 335i


yup it's the GM solenoid,how's your car running?

all you have from that picture is a boost solenoid not a boost controller that you can tweak inside the car,and it was taped from the original wiring of your stock solenoid.there's no way a stock ecu can handle that thing w/o a flash or some sort of EM.
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