What is the mesh / device in the upper portion of the OEM airbox?

 

Do you mean the carbon filter?

If so it's..well... a carbon filter.

Don't remove it, it won't help... (and one person showed a 1hp loss on a dyno from removing it, though that's certainly within the margin of error)

 

From the NCF Book.

Jeff

 

How does it not restrict airflow?

 

Air passes through it very readily.

Jeff

 

It's still an object between the atmosphere and the engine... Unless it acts to laminarize flow, it would only make the air passing through it more turbulent.

 

That's a distinct possibility. I have a feeling Lexus may have also worked some features into the shape of the airbox to help direct flow through that section with the filter as well. It's hard to know exactly without doing some flow tests on it, however I do know from experience with other Toyota models and with the IS as Kurtz mentioned, that removing the HC filter in the airbox doesn't provide any performance boost, at least not with the stock airbox/intake setup. If you changed the factors involved (airbox shape/intake length/etc.) perhaps you may get into a situation where removing this filter would provide a benefit.

That being said, I haven't heard of issues with removing it either, so if you do choose to remove it, there shouldn't be any problems.

Jeff

 

I was looking at the charcoal filter just yesterday and was hoping it was something that would pop in/out of there...but that's not gonna happen. I'd leave it in there personally.