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View Full Version : Air Filer on intake.. flow rate?


diehlryan
02-27-2008, 11:42 AM
Anyone know what the flow rate is on the factory filter?

I'm thinking k&n flows better but I want to know how much better before I go buy anything.

Search yielded me only results about a CAI (AFE Filter) and I doubt the wifey wants an open element filter on her X3.

rs6654
02-27-2008, 12:45 PM
Here is a test some guy did a while back:

http://www.duramax-diesel.com/spicer/index.htm

UncleJ
02-28-2008, 08:12 AM
rs, thanks for the link. Very interesting, even though it was for diesels, sucking air is sucking air, and the results would probably mirror closely a test with gas engines. I was surprised the Delco filter did so well and the KN did so poorly. I have always replaced my air filter element with an K&N unit but now I wonder if it was a waste of money.

diehlryan
02-28-2008, 08:26 AM
I understood that link to show that K&N flowed the most air but trapped the least amount of material.

rs6654
02-28-2008, 08:56 AM
I've always been a little suspect of K&N air filters ability to flow so much better while still effectively catching the minute particles that will scour our cylinder walls if they are not stopped. To me K&N air filters look very much like chain saw filters which are normally only catching sawdust which is big. Beides that they are protecting an engine that is only worth a few hundred dollars at best.

Another question I've had is "do our engines really need any more air than a factory filter provides?". I've concluded that for me the answer to that is no. If I were running my engine at WOT for hours on end like racing cars do it would probably help to have more flow but I suspect that paper filters are more than adequate for the way I drive day to day.

I'm a big advocate of OE filters for my BMW (both oil and air). I'm sure some other's are just fine but I feel better running what is approved by BMW. Judging by BMW's "spare no expense" engineering principals I can't imagine them providing anything less in filters.

I also run nothing but OE oil in my '07 328i and will do the same in my X3 when I get it (I change my oil ever 5K). It's priced pretty close to the major brand synthetic's and it's what BMW is asking for so I say why not.

diehlryan
02-28-2008, 09:19 AM
I dont believe in the spare no expense engineering principles. BMW is around to make money and thats what they'll do.

As for OE filters, I'm sure they fall somewhere in the middle of efficiency and protection. K&N may not be the best, but I can't imagine its any worse. Flowing more air, is still flowing more air. Even at half throttle the engine is still working to suck air, why not make it easier?

I can't really speak about oil but I'll probably use Mobil 1 when I change the oil after the maintence plan expires.

rs6654
02-28-2008, 09:50 AM
I dont believe in the spare no expense engineering principles.

The N52 engine alone is proof enough to me that BMW does not stint on engineering.

http://www.mwerks.com/artman/publish/features/printer_960.shtml

http://www.mwerks.com/gallery/gallery2.php?mode=album&album=/BMW/Technology%20and%20Development/BMW%20N52=Inline%206%20Engine#

diehlryan
02-28-2008, 10:37 AM
The N52 engine alone is proof enough to me that BMW does not stint on engineering.

http://www.mwerks.com/artman/publish/features/printer_960.shtml

http://www.mwerks.com/gallery/gallery2.php?mode=album&album=/BMW/Technology%20and%20Development/BMW%20N52=Inline%206%20Engine#

Yeah I saw that. The show Ultimate Factories focused on BMW for one episode. Regarding that engine I'll agree with you engineering assesment however when it comes to other areas, specifically the filter in this case, they spared expense.

Mystic1
02-28-2008, 11:08 AM
If you are truly worried about filtration but still want an aftermarket filter, Dinan sells drop-in as well as a CAI, and they are approved by BMW to run on all BMW's. I think it is around $300 for the CAI, and about $50-60 for a drop-in. I am not saying they will trap as much as the OEM filter, but if BMW says it's OK, and if there is an issue, they will cover any damage it causes under the warranty (if you still have one).

diehlryan
02-28-2008, 11:10 AM
If you are truly worried about filtration but still want an aftermarket filter, Dinan sells drop-in as well as a CAI, and they are approved by BMW to run on all BMW's. I think it is around $300 for the CAI, and about $50-60 for a drop-in. I am not saying they will trap as much as the OEM filter, but if BMW says it's OK, and if there is an issue, they will cover any damage it causes under the warranty (if you still have one).

Yep, its a K&N.

http://www.dinancars.com/store/Engine-Tuning-p-1-c-467.html

rs6654
02-28-2008, 11:50 AM
.....however when it comes to other areas, specifically the filter in this case, they spared expense.

Do you have any evidence that factory air filters allow harmful amounts of dirt to pass or do not flow enough air? I'm not trying to be a smart a** either. I honestly want to know. I've always thought that factory air filters flow much more air than regular driving will ever need...... The drinking out of a fire hose thing.

diehlryan
02-28-2008, 11:56 AM
no evidence. just my opinion based on different things I've read.

rs6654
02-28-2008, 12:28 PM
I started sticking to OE after an aftermarket car charger trashed my brand new cell phone. Neither Verizon or LG would do anything because it was not an LG or a Verizon marketed charger. So I ate the cost of a replacement cell phone.

Ever since then I am OE all the way. If a BMW whatever filter or part fails and trashes the engine then BMW will have to fix it. If I use Billy Bob's part and it fails BMW will tell me to go see Billy Bob. Billy bob will drag his feet and make me sue him to get my car fixed. Billy Bob's lawyers will say it was the brand part I used before I started using Billy Bob parts and I'll lose. Billy Bob will countersue me for his attorneys fees and I'll be carless, broke and pissed. OE just makes me feel better.

diehlryan
02-28-2008, 12:35 PM
I started sticking to OE after an aftermarket car charger trashed my brand new cell phone. Neither Verizon or LG would do anything because it was not an LG or a Verizon marketed charger. So I ate the cost of a replacement cell phone.

Ever since then I am OE all the way. If a BMW whatever filter or part fails and trashes the engine then BMW will have to fix it. If I use Billy Bob's part and it fails BMW will tell me to go see Billy Bob. Billy bob will drag his feet and make me sue him to get my car fixed. Billy Bob's lawyers will say it was the brand part I used before I started using Billy Bob parts and I'll lose. Billy Bob will countersue me for his attorneys fees and I'll be carless, broke and pissed. OE just makes me feel better.

I'd quit buying from a guy named Billy Bob! ;)

Mystic1
02-28-2008, 12:43 PM
I do not know wether BMW OEM filters are better/worse than aftermarket, but in other vehicles, a CAI will definately flow much better. On my stock supercharged F150, a CAI let it breath better to the point of an extra 1-1.5 lbs of boost (about 10 hp), and it was proven on a dyno. BMW filters might be better than Ford's (I hope so) but increased flow will definately help the engine perform better.

rs6654
02-28-2008, 03:26 PM
I'd quit buying from a guy named Billy Bob! ;)

A wise move for sure.:thumbup:

As of about an hour ago we're one step closer to our X3 as our daughter just got approved by BMWFS to buy our 328 (she went through a nasty divorce not long ago and her credit is not the best so it was not a done deal).

My wife retires in September and we need to slim things down a bit so an '08 X3 will replace the Tacoma. The Tacoma has been a good truck but it's seats are not the best for an old back injury so it's impractical for all the travelling we have planned. The 328 has also been perfect and has wonderful seats but what we really need now is a combination of the two.

This site has been a world of good information and very helpful in the decision making process.

Of course if I have problems I'm blaming all of you current owners.:p