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Old 10-23-2022, 07:18 PM   #1
StiLimited
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Join Date: Jul 2006
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2007 Sti Limited
Urban Gray Metallic

Default Removing the sound resonator on the Secondary Air Pump

Hello,

I have a 07 Sti. Mostly stock. I have the manifold off to replace a torn turbo duct intake pipe. There is a black resonator chamber under the intake that goes to a wye pipe/hose from the air pump to the secondary air valve at the back of the engine. Assuming I keep the valve and air pump, what is the effect of removing the sound resonator? I mean how much noise is there when that thing runs? I've never even noticed it at start up.

This thing:


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Old 10-31-2022, 03:24 AM   #2
Subie_
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Join Date: Apr 2015
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Crystal gray metallic

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I removed it & plugged it on my 07 STI. From what I recall, there were no ill effects, but I can't remember if this was before or after I deleted/deactivated the system though, so it's a 50/50.
It's an annoying part, because you need to lift, if not remove, the intake manifold to get it in/out.
Something tells me it's more functional than just sound damping. I'd have to look at a diagram of the system again, but if my memory serves me right (& had to guess) the part might have compensated for the lack of volume in piping that would have bridged to the other head. In the 2007 STI, the RH head came with a block off plate - there was only one valve (& consequently less piping) whereas the 2007 WRX had 2. The 06 STI may have been the same.
In my world of design engineering, creating a cheap part is sometimes easier than re-coding/tuning a control system knowing you'll revamp the whole thing next year (2008+). 2007 is a black sheep. I wouldn't be surprised if system design got cut mid-development and they tossed a baffle in to bridge the gap to the next major model change in 08.
Hang onto that kidney reservoir thing if you do remove it. People are out there looking for them to maintain the oem system & they aren't available from Subaru anymore. I passed mine forward for free to someone looking for one a few years ago.

Last edited by Subie_; 10-31-2022 at 03:37 AM.
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Old 10-31-2022, 08:43 AM   #3
StiLimited
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Thank you so much! I think you are right about the extra chamber area to compensate for the lack of a valve on the other side. That makes the most sense. I'd really like to ditch the whole system but.... You know what that means.

How much does that air pump and valve weigh? (If you recall.)
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Old 11-03-2022, 08:46 PM   #4
cproo12
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What does ditching the whole system mean? Get some block off plates for the heads, plug whatever holes go to the intake, and tune out the code open source.

Did it on mine, makes working on car way easier with all that tubing out of the way.

Quote:
Hang onto that kidney reservoir thing if you do remove it. People are out there looking for them to maintain the oem system & they aren't available from Subaru anymore.
Agree with this.
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Old 11-07-2022, 03:25 AM   #5
Subie_
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Quote:
Originally Posted by StiLimited View Post
How much does that air pump and valve weigh? (If you recall.)
Not much. The pump is maybe 5-8 lbs. The valve, only 1-2 lbs.

You need to keep the valve because the atmospheric pressure sensor is integrated into it. The sensor can be removed from the valve, but not easily - it's epoxied in.
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