Are K&N Panel Air Filters Really Worth It?

I'm stepping a bit out of chronological order with this post, nevertheless, here goes. During the turbo replacement job Auto Technik also replaced the standard panel air filter, which was a bit annoying really as I'd hoped to upgrade it. As such it seemed a bit wasteful to upgrade a brand new part, resulting in plans being put on hold for a while (as did the £3k turbo bill...)

I'd been drooling over the Injen SP1125WB dual intake for a while but couldn't stomach the £400 bill. Happily though, I stumbled across a hardly used, second hand K&N panel air filter listing on eBay. Chancing my arm I made an offer, a rather cheeky one at that, which was surprisingly accepted. I'd bagged it for £22.75 posted, not bad when these things are just under £60 new.

Being second hand wasn't a problem either, these things come with a 'Million Mile Limited Warranty®' and I'd got a recharge kit left over from when I fitted a K&N panel to my Rover 25. Impressively, it even came with the original packaging.

After 8 months, the standard panel filter was pretty clean, a stark contrast to my E46 330d that used to vacuum up leaves, flies and all sorts.

Head over to the workshop to read the how-to guide on replacing the air filter. It is an easy job, most people would question the guide's existence entirely, but my thinking is, if I can stop even one person being overcharged at a dealers for this job then it'll be worth writing up.

So, the million dollar question, does it make a difference? Not really... 

Don't get me wrong, I'm glad I bought it, but humour me while I explain.

Weber's law states - the more intense a stimulus the larger the change must be before it’s noticeable. i.e. The N54 335i puts out 300+bhp, to actually notice a difference you need to add proportionally more horse power than you would to a car that puts out 100bhp.

Realistically, you could expect this filter to add a maximum of 5bhp, if you notice a performance difference, it's definitely placebo.

Having said that, I did notice a difference to how freely the engine revved and a slight exhaust note change, both for the positive, which is backed up by this video showing the airflow difference between a standard paper filter and a K&N filter.

Would I pay full price? In a word, no.

Cost wise, it would take 3 years to break even fitting a K&N (at full price) vs buying a stock paper filter (at roughly £17 each).

I'd be looking towards the exceptionally good 'bang for your buck' Burger Motorsports Dual Cone Intake at around £120 from ML Performance, which replaces the standard air box and has been dyno proven to make a noticeable, real world, increase to performance. BMS claim gains of "15+ Horsepower at the wheels with no other modifications" are achievable.

Let me know what you think in the comments below, which intake setup have you gone for?

Don't forget to subscribe by using the Follow by Email widget in the top right for plenty more content to come. You can also Like and Follow me on Facebook, AndyBuck, to keep up-to-date on all my new content.