Brdman*

Though not cheap, obviously. I'm not sure if it's the same shape or design as the 12V one:

<img src="http://i16.ebayimg.com/07/i/000/fd/22/d844_1.JPG">

<img src="http://i16.ebayimg.com/04/i/000/fd/22/d54b_1.JPG">

<img src="http://i23.ebayimg.com/03/i/000/fd/22/d70a_1.JPG">

<img src="http://i6.ebayimg.com/01/i/000/fd/22/d971_1.JPG">

<img src="http://i2.ebayimg.com/08/i/000/fd/22/dba6_1.JPG">

quattro90S6

if the lower end is better

VAP

and all 3 closely resembling the B4 box. But I "think" that modifying the B4 box to be the best solution as I just don't have the heart to start with a new $700 airbox and butcher it. Even used RS/S/944T airboxes are risky due to lid warpage and cracking which is the bane of B4 airboxes in salvage yards. And used any european box will cost half as much as new plus shipping from a euro salvage yard. At current currency exchange rates none of those are as attractive/viable considerations when compared to a B4/VS conversion. Those cars had turbos that could suck-start a Harley thru their airbox inlet! We arent nowhere near that lucky! Due to our normally aspirated power-plant I personally believe the inlet OD on those to be still a little too small for maximum efficiency and/or any "if you're gonna be a dog, why be a Chihuahua" philosophy is pursued. You can still virtually kill the RS/S/944T inlet flow/volume-wise with a more contemporary/efficient VS design than they knew about or were using "back in the day."

But it was a pic of that airbox many years ago that planted the seed that just bloomed the past few weeks for me. And to think I came VERY close to kicking it to the curb first time out!

Brdman*

For some reason the S2 guys want the RS2 box. Not sure of the difference.

VAP

and exceedingly difficult to find in ANY condition other than scrap plastic. I fully believe Audi "got it" early on and put a LOT more emphasis on induction in the vintage performance cars than the contemporary performance offerings, not to mention the complete lack-luster stuff found in their passenger car "non-S" lineup. Those airboxes just LOOK the part! And I also belive the B4 is the last of the watered-down performance boxes and entirely likely the identical bottom half of the S/RS design with a smaller inlet. Virtually the same box as RS2 with a reduced inlet and "outside-the-box" MAF setup. And maybe a slightly different frame mounting arm. But gonna set someone back a seriously thick pile of pelts to confirm it. Any comparative look at the B4 lower box alongside the S/RS lower boxes would visually confirm uncanny similarities. My bet is it's identical in EVERY way with a larger inlet. But I didn't feel strongly enough about that to buy one and make it even bigger! Not when I can get a box/lid for $50 locally but admittedly have to sort thru 5 to find one top/bottom that's dimensionally/mechanically perfect!

VAP

in determining if the lower airbox is same as B4. Not "conclusive" evidence but one more step that direction.

B4 filter element part# stamped on B4 airbox lid: 191 129 620

Brdman*

Upper:

<img src="http://www.showyourmedia.com/files/1216682902.jpg">
RS2 on bottom.

"The RS2 lower section is smaller so the air filter sits lower, allowing a greater volume in the upper chamber. This means that on the RS2 box, the chamber after the filter has a larger volume than the chamber before the filter, allowing a faster and greater air flow (apparently)"

Lower:

<img src="http://www.showyourmedia.com/files/1216682936.jpg">
RS2 with larger inlet on the left.

Both use the same filter, part number 191 129 620

VAP

I suspect lids actually had reduced volume comparatively speaking to say a B4 lid due to the internal VS and MAF provision. Tho wouldn't surprise me to find the RS2 had more volume than the "S" version.

Brdman*

<img src="http://www.showyourmedia.com/files/1216684816.JPG">

<img src="http://www.showyourmedia.com/files/1216684852.JPG">

<img src="http://www.showyourmedia.com/files/1216684888.jpg">

Source: S2Central

VAP

clamp styles used between the B4/RS box. I see 2 common and all others different related to location. An absence of the midline front-to-rear inboard (engine side) clamp on the RS box (due to heat-shielding) would concern me as the biggest reasons these lids warp is from a lack of sufficient clamps used spaced closely enough together to prevent distorting the lid when clamped shut. And the B4 has at least 2 more clamps and maybe 3 than the RS box unless there's some integrated or different clamp method used I'm not picking up on. But If I REALLY wanted to go this route and have bragging rights to having a real-deal RS2 box (or at least the bottom half of one) I'd probably bring a bottom over from the UK and modify it to have "at least" as many clamps and at the same location as the B4 lid has reinforced areas for those clamps. I think ALL these airboxes could benefit by a stainless airbox lid "bezel-surround" that would sit over the clamping edge and distribute the clamping pressure over a greater area.

The biggest question I have is about the efficiency of that box with a custom-sized and fitted, more up-to-date &amp; efficient full radius-edged velocity stack inlet design for the RS2's in Europe. Something strictly plug-n-play that could be "undone" without any compromise to the stock OEM components due to "purist" value. But there's GOT to be a few cheap/easy ponies laying on that table!