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Just was poking around today and saw that there is a good sized crack in my intake box on the left hand side below the filter. I don't think it's going to hurt anything as it's on the bottom side and the air is going to get filtered anyway. I know some people even drill holes in that part of the box for more air It just made me think about making my own cone intake. There are no aftermarket systems that I know of and seems like it would be more efficient.....
Who's made their own and was it worth it?
Were there any improvements besides looking rad and bragging rights for building it yourself?

Unless you do a really complete job of shielding hot engine air, a better idea is to extend the stock airbox snout to the headlight bucket area

What about the improved airflow through a nonstock filter? Is it possible to buy a box filter that is equivalent? Or is the advantage negated by the intake of warmer air (assuming the cone filter is not extended)?

Would like to know this myself!

I look at it this way. There is something to be said for CAI's but the 'folks' that engineered these cars knew what they were doing including calculating air intake and parts design. The jokes (problems) with some design and maintence features is OVER engineering.

Yeah I'm sure you wouldn't see much of anything making intake mods on a stock car. I don't doubt bmw's work as the box seems to be pretty straight flowing and in the best place it could be for sucking cool air. If you had a 3.5 swapped and some other work like exhaust(still way down the road for me) I do wonder if it would do anything to upgrade the breathing. Like continuing the intake head farther for more cool air and heat shielding as suggested, and replacing the box in favor of just one straight pipe. Assuming a k&n cone can flow just as much or more air then the k&n box filter....

Anyway like I said way down the road for me. Just curious. I just ordered some of the grassroots motorsports e12 project issues so maybe they tackle that.

I doubt there would be much gained, but if you really want a CAI, at least on a budget price, I'd look at adapting one off an E28. It has a hose leading to the cover in back of the headlights, so it's drawing air from up front. Nice in theory, but like I said, I don't think anything to speak of would be gained.

I don't think there's much to be gained from a cold air intake. I've not noticed any change in power on my car between when the air is cold (near freezing) or really hot (over 100!), so I didn't bother with the cold air intake.

I did take the "silencer" off my Ford which consisted of a convoluted cast plastic unit that added a good metre to the intake length. Ran a bit of flexible 3" hose from the front and it made the tiniest difference. Sounded a little better though.

There's 2 items in FAQ on how to make one from the headlight cover to the box.

Cheers

This one is sort'a bitchin' -

This ... I LOVE ( need to dig through the garbage for that Pringles can I just threw out ) ... all I will need is some fresh duct-tape ( or duck-tape )
Cheers !!

Looks like you are running two flavors from the look of those cans. Original and....COOL ranch? That would help with the cold air part of the intake correct?

I tried to buy pipe of some description to extend the original air box to behind the headlights, with no success, and whilst tipping a tin of baked beans into a pan to warm tham, I looked at the aluminum can in my hand, mmmmm, I got 2 of them, opended the bottom as well, taped them togethere with duct tape, and taped them to the original airbox, free aluminum pipe,

I cleaned them first, I figured baked beans would do nothing for the mix/octane rating, although if anyone has tried different sauces and got a power increase, let us know,

I also drilled some small holes in the air box, right side of the filter, seems to work good with the bean cans,

Your best bet is to head over to the wreckers and find an E24 (non-M). You can use the right side headlight cover (with a large hole in it) and the accordion tube that will fit directly into the current air box on our cars.
It fits like a glove.

No. 13 is what we already have. Replace it with the below components along with a drop-in F&N filter if you'd like and you're done.


No. 19 and 20


and No. 10

I never thought the day would come where people started to use pringle can's as tubing for cold air.. hahah

I just bought a cone filter (Canadian Tire- $40) and luckily enough, it fit the existing diameter of the intake plenum.
I left the existing airfilter holder to block out
some of the heat coming off the intake manifold.
I cut a hole in the headlight cover also for a little for direct airflow into the collector.
I would say it is worth it, not so much performance wise but aesthetically and the whistle sound it makes will say it all.
I also did notice a small increase in my gas mileage, only about 1-2 MPG
As for the pringles and duct tape, I disapprove

I think the cone filter is not worth it for the sake of performance. My 3.5 pulls strong to the rev limiter thru the stock air box and filter. There's some work on the exhaust, and I rounded off all the sharp corners in the AFM, but all I did to the air box was replace that venturi inlet thingy with a hose to a hole I cut into the plastic cover on the back of the headlights. The hose was just an air duct I got from local parts shop -- measured the diameter and cut to length.

The cone filter looks cooler, and sounds meaner.