So what's the consensus on the best drop in air filter that will not set off the CEL and provide the best gains? K&N or BMC?

Jon

 

You will find most of the gains are bs. Some will even say you lose some bottom end torque. If you get an oiled one make sure you wipe it down before you install it. MAF's don't like the excess oil.

 

But in conjunction with mufflers and an ECU tune, I'm sure it heps with overal airflow/breathability? I would imagine doing nothing but a filter and expecting any gains is bs as you said though.

 

I use the K&N on my 997 and all of my other vehicles too. I really don't expect any noticeable impovement in performance, but I do know I get better filtration than with an OE paper filter. Plus the K&N will pay for itself in short order since all you have to do is pop it out an clean it.

 

Do you have a reason to think you get better filtration? I have never seen that claimed let alone demonstrated. Cleaning and reoiling can cause MAS contamination or insufficient filtering if not done just right. That alone would make me crazy. Racing motors using "high flow" filters are rebuilt often so filtration/wear per se is not usually a consideration. Imo, long term ownership is better served by oem filter with frequent replacement. Filters are cheap. Why mess around?

 

When I had my stock air box, I put in the BMC filter. I noticed that from 5500+ onward, the engine was able to rev more freely, and feels less choked. No CEL's were ever recorded or noticed.

I would be very surprised if one makes significantly more HP than the other. You can't go wrong with either one, if you choose to go this route.

 

My opinion is based on years of experience running and maintaining heavy duty trucks, off road race vehicles and lots of personal cars that I put very high miles on.

I do oil analysis via Blackstone every other oil change. When I run OE paper filters you see a noticeably higher silica count than you do with a K&N (or similar brand cloth filter) oiled filter. That makes sense because the K&N, even if not oiled, has a higher micron filtration capability.

The key with any oiled filter is to clean it often and prep it correctly. I have never had a MAF issue and as long as you don't over oil the filter you shouldn't either. For a 911 a K&N filter only requires 2oz of oil. You also have to make sure you only oil the underside and not the top.

The worst thing you can do is install a CAI type "filter on a stick". It may sound better and give you a tiny bit more oomph but the filtration is not very good, even if you run a pre-filter sock over it.

 

I've always run BMC on my stock airbox as well as my new X51 airbox. No CEL's and I did notice a performance difference. My car idled smoother and picked up a little more with no more hesitation that I was getting with the stock filter.