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ESIS (modified stock air box) mini update

8415 Views 6 Replies 3 Participants Last post by  31st330i
my new OEM E36 air filter just arrived ($9 from Pacific BMW) and I confirmed Shawn Fogg's findings. the filters are interchangable and I have confirmed that the E36 filter has 26% more surface area and NO foam layer.

edit: actually, the surface area numbers can be multiplied by two because I forgot to figure in that each pleat actually consists of two sides.

E36 filter
pleat nubber: 81
pleat width: 166mm
pleat depth: 46mm
surface area: 618,516 sq. mm
part number: 13 72 1 730 946

E46 filter
pleat number: 82
pleat width: 166mm
pleat depth: 36mm
surface area: 490,032 sq. mm
foam layer heigt: 9mm
part number: 13 72 1 744 869

so for those of you who are as stubborn as I with regard to retaining the stock paper filter, you can use the E36 filter. do NOT use aftermarket E36 filters from companies like Fram. I purchased one and counted the pleats on it and found that it actually had a REDUCED surface area comparet to even the E46 filter.

on the air box mod itself, I cut the new tube in half. the opening was cut at an angle to make it effectivly larger than the inner diameter of the hose itself. furthermore, I used the flared end of the radiator hose INSIDE of the air box this time. I trimmed the flare way bask so that the tube doesn't protrued into the air box as much and so that there is sort of a mini reverse velocity stack shape.

anyway, so far, just the extra inlet tube seems to make a difference. I just noeed to recruit a local 330 owner to validate my findings.

so far, I have into this project:
radiator hose for the new inlet: $10
hole saw (to cut hole in air box): $14
E36 air filter: $9

I don't count the OBD-II software that I use to take the measurements because I would have purchased it anyway.

here is a pic (courtesy of Shawn Fogg's web page) of the two filters side by side:

anyone wanting to follow the progress of my air box mods along with the insualtion work of Kevin_21_325ci should follow this thread on e46fanatics:

once my project is complete, I will be posting a DIY on my home page.
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The "other" air intake idea

Hey 31st,
I was reading one of your earlier posts about installing an ITG air filter and housing, resulting in a Dinan/ECIS compromize intake.

I had been on the ITG site before and requested a quote for the filter and housing. It's not quite as cheap as I thought it would be. They want 470 pounds ($685) for the housing and 48 pounds ($70) for the filter.

They are sending me the dimensions of the housing by post today.

It sounded like a great plan and I really like the ITG filter.
I was thinking along the lines of the Conforti intake for about $400, but I'm interested in seeing how your airbox mod works.

I like the big $$$ savings!!!:thumb:

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:yikes: WOW:yikes:

that's a high price. thanks for checking into it. I figured it might be a little pricey but $700+ total makes it cost prohibitive. thanks for checking into it.
by the way gang, I discovered that the rubber frame around the E36 filter is very slightly larger than that of the E46. it could be that I just had a pooely cast sample but it was easy to install none the less. the trick is to remove the duct from above the radiator and install the filter into the air filter housing *lid* versus into the bottom. you may need to push the rubber frame down into the groove of the air box using a screw driver but once done, it stays in place and you can assemble the airbox then put the intake tube back on. the E36 Fram filter that I tried fit perfectly, this is why I suspect that the BMW filter was just mal-formed from the factory.
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Hey 31st

Have you tried the ITG drop in filter?
I was wondering how that would perform vs. stock or M3 filter.
I was thinking about getting one for my 330Ci

Any thoughts?
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Re: Hey 31st

Samir on E46fanatics dynoed his 330i w/ both the stock filter and the ITG. The car gained a few horsepower.
I haven't had time and have somewhat abandoned the project for the short term. I'm knee deep in miata at the moment. ;)
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