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Discussion Starter #1
After driving for a while with a Drop in K&N filter I noticed the throttle response improved slightly but not a whole lot. I decided to go looking for air intake obstructions and I found a few interesting items.

First, to my disbelief there was a pre-filter on the upper air box lid with a plastic support system that has to screw up the flow. I am betting this has to do with the SULEV rating of my car as it looks like a carbon/charcoal type filter. Does anyone else have this on their 2.4? Who in the world would put a non-removeable prefilter on a car??? This makes no sense breathing through two filters.



I removed it carefully not to break the structure which was plastic riveted to the lid. Here is the bottom of the prefilter (that waffle design has to hurt flow!)



Removing it produces a higher flowing cavity!



Also interesting is that the ECU is cooled by incoming Air! Yes, that's right a hot ECU is in your airbox. I am puzzled on this design as well--I wonder how it stacks up against the hyundai version of the airbox.



I will ultimately go with a self-fabricated intake which will go down to the area behind the driver's fog lamp. There is plenty of area for the tubing and filter. The air down there would certainly be cold. I plan to do a remote thermoprobe to prove that out before I make the intake.

If you have an SX please let me know if you have this crappy pre-filter.
 

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Discussion Starter #2 (Edited)
Well after some research this is part of the SULEV spec. This is most likely what is robbing a majority of the HP in CA models (it's rated at 8hp less). There is no mention of ECU retune so it's all about flow and keeping HC's in and burning them.

HC block in the air intake system:

Hydrocarbon escape via the intake system is prevented due to the use of an additional carbon filter (1) incorporated in the air filter housing and a "closed" throttle valve actuator (2).

Fuel system components:

All metal fuel system components (fuel rail (1), injectors (2), tank ventilation valve (3), etc.) are made of stainless steel and are fastened together using coupling type connectors (4).

Fuel tank and tank ventilation system:
The fuel tank (1), tank filler neck (2) and evaporative canister (3) are made of stainless steel.


Crankcase ventilation system:
The crankcase ventilation valve (1) is incorporated in the aluminum cylinder head cover (2).


System components used to achieve SULEV tailpipe emission requirements:
  1. "Warm up" catalytic converter(s) – high cell density technology
  2. Upstream oxygen sensors – wide band technology
I doubt that the CAT is responsible for a large portion of the 8HP. I want my ponies back and will get them!
 

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that top filter might be used for the blow back off the crank case. Like a PCV valve. That way its not dumped in the atmosphere.
 

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Discussion Starter #5 (Edited)
that top filter might be used for the blow back off the crank case. Like a PCV valve. That way its not dumped in the atmosphere.
Exactly what's it is for... Mine is now back to 50 state LEV mode. It's breath so much better-especially in the mid-range.
 

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So is this something that can simply be taken out? Or would this mess up the intake system? If it's "disposable", I'm taking it off tonight!
 

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Discussion Starter #7
Just be careful... Look at my pictures in full resolution and you will see the four little nubs as to where they plastic attached this thing.

Carefully pop these out by pulling on them one by one and save it for smog. You should be able to RTV it back in for smog if needed 7 years from now.

That's my plan.

To maximize the gain, use a K&N drop in filter!
 

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Discussion Starter #8
Wow! What a difference in driveability! The car now can breathe and move it's own weight. I am going to pull the positive battery cable to reset the computer to handle the extra air.

Yeah, I got my ponies back! This is highly recommend for those with this crap in the air intake system.
 

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not in my car

well i dont have that on my forte sx sedan 6speed :confused:
 

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You don't have a SULEV engine;)...you have a ULEV engine:)...LoL! There are five states -- like California:mad: -- that require the extra emissions control Sh...stuff:D
thanks anything for some more power!! want to change that pulley but i dont want to void that warranty
 
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