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What's this?

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More specifically, what good purpose does it serve?
It comes off the opening to the throttle body in the air box, and goes right up against the filter element.
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I'm looking at it and my air box and seeing how much available air was being limited as half the air box behind the element would have filtered air to draw, but this limited the draw to this little circle directly against the element.
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I was looking at my element thinking it may be clogged up some because of the delay in my throttle response. I could hear the labored suction when pulling the cables under my hood. I have changed my element before, but never really looked inside the box before then. I saw this. I saw the vacuum lines coming in to the box on either side behind the element, outside of this, and all that readily available air going to waste. I also saw the limit this puts on the available vacuum at the same time. Out it came.
I have since had a much better throttle AND shifting (AT) response. As an added bonus, there is a minor weight reduction.
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Brian, a non-authoritative answer: "Air intake noise reduction". Quite a bit of the structure in the intake plumbing is intended to silence the air intake "roar".
I can't imagine that eliminating that piece of plastic will cause any negative issues, as long as you maintain a good seal in the plumbing between the air filter and the throttle body.
 

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Discussion Starter · #3 ·
Brian, a non-authoritative answer: "Air intake noise reduction". Quite a bit of the structure in the intake plumbing is intended to silence the air intake "roar".
I can't imagine that eliminating that piece of plastic will cause any negative issues, as long as you maintain a good seal in the plumbing between the air filter and the throttle body.
"Sounds" like a good answer. 😆 The best answer yet even!🤣
I really had no answer myself. I'll have to give a listen next time I run her. It certainly hasn't been an obvious reduction. It might be more so if I drove her hard, but I don't usually, and on a road where I might get her up to enough rpms to be noticeable, there is so much other noise, wind alone will drown it out.
Thanks for the ... "input"?
I'm having too much fun here.
 

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could be emissions related? - fuel supply will automatically adjust to available air supply based on exhaust O2, and an intake restriction effectively changes the range that the fuel system ideally operates across. idunno, seems like a weird way to restrict flow if that was the goal...
 

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Aside from noise reduction I suppose it might help prevent the throttle body from sucking dripping water from a wet air filter into the throttle body? A little bit like roof eaves over a window? If so, it's probably not necessary except in the most extreme driving rain at high speed or something where water is going to blow into the intake system.
 

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Discussion Starter · #6 ·
could be emissions related? - fuel supply will automatically adjust to available air supply based on exhaust O2, and an intake restriction effectively changes the range that the fuel system ideally operates across. idunno, seems like a weird way to restrict flow if that was the goal...
In this point, if fuel adjust to air, then both are burning so emissions would be moot. This effectively chokes the system as it reduces the area it can readily pull air from.

it might help prevent the throttle body from sucking dripping water from a wet air filter into the throttle body
In this one, this "nozzle or snorkel" for lack of better description, was mounted in such a fashion that the flush rounded end was inside the throttle body's tube, coming out and up at an angle so that the angled end sat flush and in contact with the element. If somehow despite all engine design the element got wet, much less enough so to interfere with the engine, this snorkel would assuredly suck moisture through and off of it.

Genie from "Aladdin" comes to mind. "GREAT BIG AIR BOX!. little bitty sucking space."🧞‍♂️

Noise reduction may be it. Unless we get an answer from a designing engineer or someone as knowledgeable to tell, we'll never know. I'm sure we'll have to resort to torture to find out even then.
I started her today, and have to say at the high idle in the cool temps we're getting since I removed it, she does sound a bit more sport car growly like.
 

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Well, it looks like a "velocity stack", and I suppose that could be its intended function, but having its intake occluded by the filter element would seem counterproductive. Probably some enterprising engineer running intake airflow simulations found a tiny performance boost, and managed to get it incorporated into the airbox design?
Just FWIW, at some point in the early 2000s, Subaru moved the air filter element from a box on the passenger side wheel-well, to the larger box just behind the throttle body. This might be a carry-over from that design transition? There just ain't no way to know, but I can't imagine it making much difference, regardless.
"Velocity Stack" sounds cooler than "Noise Suppression" in any event, and gets my vote :-D.
 

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In this point, if fuel adjust to air, then both are burning so emissions would be moot. This effectively chokes the system as it reduces the area it can readily pull air from.


In this one, this "nozzle or snorkel" for lack of better description, was mounted in such a fashion that the flush rounded end was inside the throttle body's tube, coming out and up at an angle so that the angled end sat flush and in contact with the element. If somehow despite all engine design the element got wet, much less enough so to interfere with the engine, this snorkel would assuredly suck moisture through and off of it.

Genie from "Aladdin" comes to mind. "GREAT BIG AIR BOX!. little bitty sucking space."🧞‍♂️

Noise reduction may be it. Unless we get an answer from a designing engineer or someone as knowledgeable to tell, we'll never know. I'm sure we'll have to resort to torture to find out even then.
I started her today, and have to say at the high idle in the cool temps we're getting since I removed it, she does sound a bit more sport car growly like.
until we're running pure hydrogen the cleanest burning engines will still have regulated emissions that scale with fuel load, and manufacturers' fleet emissions calculations will depend on models staying within designated categories
 
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