Foam/grille in bottom of air box..?

This is on a project car, a work in progress. Was about to do some maintenance and don't remember this in my other air boxes. Anyone know what this foam thats falling apart on the bottom of air box does or is for..?

umm... venting with no bug access? wag

That looks like a nest of some kind

I vaguely remembering it having something to do with the Helmholtz box to reduce intake noise. Porsche must have thought it wasn't too important because they left it out of the 997 airbox.

Yup, that's my airbox. The material gets old and brittle. Felt like it was a 3M scrubbing pad. I removed the frame and the foam and cleaned it out. I thought at first that it was a way to collect water sucked in from the snorkel, but not sure. Underneath mine were a zillion small holes the size I see in your picture to the left of the foam. I've been running it for two years without the foam or the bracket that holds it in place, but I have been thinking I should seal it because it just sucks in hot air from the engine. I should probably just buy the 997.1 airbox on Ebay. After you remove all that crap and come up with a way to seal the holes, let us all know.

Thanks for all the replies,,, Ya, thats what I thought, some sort of noise baffle or sumtin only tutonic engineers can explain. Looked at it from every angle and seems useless, and no part number from Porsche for replacement foam. Cleaned it up, removed the grille and foam. About to put in a new air cleaner and the cleaned off MAF.

+1 hp due to clean air box. Nice.

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I was wondering about the holes too. Both the 997.1 and 997.2 airboxes have an opening that lets about fives times as much hot air in as the 996.1 version. I guess I'll have to lighten up on the people running cone filters. 997.1 box on the left with a nylon screen over the opening, 996.1 box on the right. 997.1 box with screen removed. Maybe Skip will chime in.

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996.2, ,997.1, 996.1 Seems as the displacement/airflow went up with the model years so did the holes. Must be some reason Porsche engineers decide on them. Could it be that the deck lid air intake doesn't cut the mustard in some situations and needs a little supplement air..? no matter the IAT.

Hey, Allcool! I have the same airbox holes (996.2) and this thread got me wondering, so I took some sheet gasket material, cut it to fit over all the holes, but one, and rubber cemented it into place. Took the car out and it may be my imagination, but I think it performed better and for a while, the temp gauge stayed just under its usual spot. It made no impact on the sound. Based on dirt patterns on the air filter, the majority of intake air was coming up from those holes bringing in hot air and dust. The guy with the 997 airbox with no holes gave me confidence to make this mod.

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Hey 996-CAB, maybe you've misunderstood my post, I removed the crumbling foam and the grille that holds it in, on the bottom of air box with NO holes under it . No one seems to know what this foam does, many have said its part of the sound baffling/muffling. As the pics show, holes are on the other side of airbox. my point was the holes are there for a reason, the engineers know a mix of maybe warmer air and the cool deck lid air will be introduced. Porsche engineers thought this thru better than any of us can. My guess was, under certain circumstances engine might be starving for more air with the airbox closed up no holes. Hence the holes, and as displacement/airflow increased over the years, more holes where introduced. The 997.1 air box in the pic has a fine mesh screen over large open areas to keep out debris/water(?) but is fully open as the screen lets air thru, more than likely its got the most air intake from the engine compartment of all the airboxes... This is all just a educated guess as I've got no data to back any of this up... I would never close up those holes myself, unless someone with a lot more data than me says the holes are not needed... jmo

Allcool. I have bought a couple of 996 airboxes from DC Auto and they each had a different hole pattern. I thought the foam was over the holes and I thought mine were, but clearly not. I'm going to keep the holes plugged up for now and will report back with any impacts. I do appreciate that there has to be a reason...it would cost more to make a die with pins than without, so they had to have a reason...

Anti Icing holes? especially in European winters, this goes back to Carb days but i had a Ford escort which had a little oven on the exhaust manifold that would warm the air coming into the intake if i recall correctly back to 1987 ish...

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I believe (guess) the sponge thing is to capture water that enters the box from the intake. The holes are to drain excess water accumulated inside the box (thinking washing/rain). Just my thought as I too has the original sponge fall apart in my hands. My thought is to replace with some sponge material wash rags.