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Discussion Starter · #1 ·
So got this focus late last year and I've realized that it has a CAI(cold air intake) installed, but in a weird way.

Instead of taking out the non-servicable filter they have just added another one down below. But the stock filter is still showing green on the gauge. Could this be an issue or is having essentially two filters ok? Wouldn't be much of a hassle getting an elbow and removing the stock filter, but not planning on doing it unless necessary.
 

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That thing that looks like a housing for an air filter is not what it seems. That thing is called a resonator and has no filter inside it. The actual filter is (or was) buried inside the drivers side front wheel well and is advertised as a lifetime filter. What you have sounds like a Stealth CAI and is exactly how I did my car. If done correctly, the Stealth CAI can be a very nice and cheap alternative to other choices available.

Do a web search for: Focus Stealth CAI
 

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Discussion Starter · #3 ·
Ahh thanks. Thatd make more sense than what I thought was happening. It still runs a little rough so I had thought maybe that was the cause. Thinking might need to make sure its more air tight, though. Had to tighten everything recently because something had slipped free and it was dangling by the mount. [thumbd]
 

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Resonator box has plastic stubs on the bottom that plug into rubber grommets in the body, that part is held pretty securely & the rest attaches to it & the intake.
 

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Discussion Starter · #5 ·
What exactly does it.. do? Haven't heard of a resonator box on any other car.

The part that came unattached is a looping aftermarket air tube that lets the filter sit facing straight up rather than just being directly attached to the original tube and facing straight down.
 

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Ah, the filter is most often attached directly to the bottom when doing that modification.

The alternative of using JUST the MAF tube attached to the throttle body connection is the one more often used to keep the filter high in the engine compartment.

Resonator is primarily for sound deadening, keeps the flow through the filter more even & quiet. I think the tuned chamber helps with power at low rpm myself, but it isn't an effect that's studied much here.
 
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