This thread
https://www.northamericanmotoring.co...ead.php?t=4133
details how to access the partition for venting more outside air to an aftermarket CAI/HAI kit through the cowl. It says it "won't work for a stock airbox".

With that in mind, I studied the design a little more. As there is already a small hole in the stock lower airbox that connects via a grommet to a hole in the lower section of the partition, I figured out that I could add a series of honeycomb style holes in the lower stock airbox and match it up to honeycomb holes in the lower section of the partition, and then seal off the whole thing with some foam insulation to keep out the hot engine bay air.

I chose to do a series of small honeycomb holes for structural integrity purposes (and I didn't want to go buy a 2" hole attachment for my drill ).

The foam isn't quite thick enough to seal completely on one side, so once it was all together, I doubled it up and stuffed some more around it. But these pics give the basic idea of what I did.

The supercharger whine is more apparent now at WOT , but it's hard to tell if I really added any "power". At best, I probably picked up 2 hp and added some more fresh ambient air. At worst, I wasted an hour working on my car, which is always fun anyways. And it's way cheaper than buying aftermarket parts...

My apologies if this has been done by someone already, but I didn't see anything about modding the stock airbox...

 

Looks good! I like it.
You may want to look into getting a filter that filters better than the K&N.

 

Thanks for the feedback. If not the K&N panel filter, what do you suggest?

Here's some tests comparing filtering capabilities of a few different types:
http://mkiv.com/techarticles/filters_test/2/
http://offroadpakistan.com/blog/tech...rs_work_1.html

I supposed if I lived in really dusty or offroad conditions, I'd consider something other than a K&N...

 

Here is one that should be a bit better.
http://afefilters.com/prodrys/v1.html

 

https://www.northamericanmotoring.co...=carnation+hai
p.s. i've used both the alta and uni foam panel filters, both of which i trust more than oiled cloth.

 

The foam panel filter is the best for performance. Doesn't loose as much airflow over time like the pleated ones do.

 

I'd agree that the foam filters are probably best for flow, but they seem to be very poor for filtration (according to the test I posted about)...

 

That link only tested one very inferior foam product. Here is a link to another article. In fact if you do a search for "foam air filter test" you will come up with all kinds of interesting results.......!

 

I like this one.
http://www.bmwe34.net/E34main/Upgrade/Air_filter.htm

 

I used a little trick from the miata world.
I enlarged the existing holes between the airbox and the cowl to 2 inches, I then got about 3 inches of 2inch diameter shopvac hose and connected the holes. Don't know if it did much but colder air can't hurt and it sounds nice.

 

Here's my variation on this mod:

One big rectangular hole.



One big rectangular hole, but with the buttresses supporting the rear mounts left in place.



Couldn't source the 9/16" thick weatherstripping, so I stacked 3/16" thick camper shell weatherstrip foam with some 3/4" wide by 1/2" thick stuff.



Trimmed the weatherstripping, and removed a piece near the bottom lip that was superfluous. The keenest of observers will note the extra tiny hole for drainage in the rear section of the bottom of the airbox. I figured, now that the back of the box is open and could possibly get water in there, that it would be better to let it drain there rather than make it get deep enough to flow over the lump to the next section where the factory drain is....



Just about buttoned up--just have to put the battery terminal back on and clean up tools....



To get the rectangular holes, I used a Dremel with a tiny cut-off grinder wheel, with final clean-up of the holes' shape and de-burring the edges via a file and a chisel.

Thanks for the original post, Dan00Hawk--I wouldn't've had such an easy time without your pics showing the general location of the holes and where to apply weatherstripping....

:D

C ya,
Dutch

 

Sorry to revive this OLD thread ... But has anyone noticed any difference by doing this mod? Looks super straight forward ... also my concern would be water from driving on the highway in the rain? I am in Florida and it rains alot and HEAVY . These little motors flow a ton of air and i can see how it would get sucked in at least a little ...

 

If you look behind the opening in the cowl (the hole above the foam tape), you'll see that the cowl extends below the opening. If you pop the hood on your own car and peer down into the cowl area, you'll see there's a drain at the bottom where water can drain out. It'd have to be raining awfully heavy to fill up to the point where the intake opening in the side of the cowl area would draw in water....



I noticed a small improvement in zip at high rpms (I bounced it off the rev limiter a few times until I got used to it), but mostly it's a nice way to hear the supercharger better. The one-ball exhaust mod added more (the car felt as if it had finally coughed up a hairball it was hacking on), and it did it across the board rather than just at higher revs. Plus, now I can shift by ear a bit easier because I can hear the exhaust note a little bit....

I expect that the airbox mod will make more difference when I finally bite the bullet and put a 15% pulley on the super....

C ya,
Dutch

 

Yea I guess I'll have to go take a look at mine. I was thinking more as the rain was dripping / falling from the top to bottom and on the way the suction of air would draw the drops into the box... no so much as it filling up But I hear ya ... I was thinking of this as prep for my soon-to-be pulley also, rather than dropping 150-200 bucks on a "real" CAI. Thanks for the quick reply too

 

It might draw a few drops in the opening, but the bottom of the airbox has a small drain hole that would let any accumulated water drain out. A few drops getting on the air filter would evaporate from the air passing through the filter, just making the incoming air slightly more humid....

As far as "real" is concerned, the idea for this was lifted from Porsche's racing team, so this method's got some "real" racing pedigree....

C ya,
Dutch

 

Looks good!! And I agree with you quote!