Air filter above the air filter??

[Shinare]

When changing out my air filter the other day I noticed when I poened up the OEM air box there was a thinner darker filter above the main filter up inside the top part of the box. Does that need to be there? It looks very dirty and wondering if I need to replace it or take it out.

[RedRide]

That is pat of the air pollution prevention. It prevents gas fumes from venting into the atmosphere .

Strangely enough, experiments in removing it (and doing nothing else) seems to make little difference in performance and even at that, only in the extreme top end if anything.
It actually allows much more air flow to the engine than you would imagine it would

BTW, it is not dirty. It supposed to be grey in color.

I would leave it in. :smile:

[Kaotic Lazagna]

Someone on a Lexus forum played with it. Dyno'd their car with the carbon trap (I think that's what that piece is called) and without....engine made less power with it off. lol

[Betrivent]

^ because science.

[RedRide]

It should be remembered that it is indeed a "hydrocarbon trap" and not an air trap.

[Shinare]

Thanks, I was just wondering seeing as how all these aftermarket intakes probably don't have one, just wondering if I needed it since it looked very "dirty". Seeing as how that's how it is supposed to look, I'm fine with it. heh :)

[CrankyOldMan]

It's a charcoal/carbon filter. Technically, removing it is in violation of EPA regulations, blah blah blah, but in reality it could make a very small difference in the intake airflow. I would also take the dyno test with a grain of salt, unless they did 3+ pulls in a row for each configuration and compared the average of the two.