[mjacob23]

I'm looking for a little power and possibly some sound and thought a cold air intake would be a relatively cheap and easy option, what are some popular and good options for my 2011 328ix?

[3PedalJake]

Depends on what you mean by "cold air intake". If you mean the open filters in the engine compartment those are better called "hot air intakes" and will lose power on a N/A engine (OK for turbos). The popular upgrades for airbox is the aFe intake and the "euro" style intake, reviews are mixed over whether they're really a power upgrade, ditto the K&N dropins for stock airbox.
A silicone intake boot to replace the stock boot with the silencer chamber will give you more induction sound, sounds good but again marginal power gain at best.
The best upgrade you could do for power is a 3 stage intake, that's a bit past "cheap and easy" tho.

[mjacob23]

thanks for the reply and info, Do you think replacing simply the intake boot and nothing else would really add sound? and would after market silicon boots have places for o2 sensors?

[3PedalJake]

There is a noticeable increase in the intake induction sound. It doesn't "add" sound per se, it just doesn't deaden it like the OEM boot does with its big silencer chamber underneath. There are no sensors on either OEM or aftermarket boot. O2 sensors are on the exhaust manifolds, and the MAF intake sensor is on the filter box upstream from the intake boot. It's just a air pipe, it's the simplest mod you can do and it will give you a chance to take your intake apart and see how it goes together if you want to upgrade the airbox later (expensive). A K&N dropin filter for the stock airbox flows a little better, but that's because it filters less so it's a values call but you might get 1 or 2 HP from it.

Don't lose the rubber gremlin butt plug under the airbox when you take the airbox off...

[fravel]

+1 for the euro airbox - it's worth it just for ease of filter changes alone. Stock design requires you to remove the whole airbox. With euro airbox just gotta take the lid off.

[hassmaschine]

You already have a cold-air intake. It's the factory airbox, which has ducts to draw in air from outside of the engine bay. It's almost like BMW spent money engineering the car or something...

if you want to spend $200 to get a euro airbox to make a once in 1-2 years air filter change easier, have at it. but functionally it's pretty much the same as the one you already have.

[eljay]

All that needed to be said, was said. Listen to the above.
The only cold(er) air is outside the engine bay and that's what the factory intake draws in.

If you want to spend money on looks and loose performance, get a cone filter.
If you want a bit more induction noise, do the silicone elbow.
If you want to spend money on looks, save some time on filter changes, keep stock performance, get euro intake box.

[macloren]

Originally Posted by hassmaschine

You already have a cold-air intake. It's the factory airbox, which has ducts to draw in air from outside of the engine bay. It's almost like BMW spent money engineering the car or something...

if you want to spend $200 to get a euro airbox to make a once in 1-2 years air filter change easier, have at it. but functionally it's pretty much the same as the one you already have.

This. Also, aftermarket CAI's won't provide huge power gain.

[Biginboca]

I agree with everything above aftermarket CAI is just pissing away money for no gain, but I do also feel the Euro intake is worth a few real HP, especially coupled with a silicone elbow. Here’s a video I took showing a Stock US Airbox panel filter next to a Euro Airbox round filter. The euro filter flows much more air as you can see the surface area is about double as much.

While the stock Airbox is good and well engineered the Euro Airbox is even better from the same engineers lol

And if you want more intake sound do the Dinan ram mod to the euro Airbox. That combo gave me a ton of induction noise:

https://www.e90post.com/forums/showthread.php?t=1696371