Gatriel

I found it entertaining, and somewhat sad that many of you get so upset over the prospect that your K&N air filter is letting more crap into your engines. As Paran points out with airfilters, its a "give & take" -- what would you prefer -- greater airflow or greater filtration.

So lets say you go with the K&N and stock exhaust -- there is something called "backwards force" when dealing with exhaust one must take into consideration. It is the pressure required to be within the exhaust system (from the headers on back and out) to move exhaust away from the engine and out the back as efficiently as possible. This force is designed with a tolerance to accept the accumulating dirt (and therefore reduction of airflow) over the life of the OEM air filter. It is not designed to accept an increase in airflow without screwing up the pressure within the exhaust system .... why? $$$ or in BMW's case €€€

The exhaust system is not just random piece of pipe BMW pulls out of some scrap yard & says "yeup -- that'll work" and throw it on the car. (Come on, BMW isn't GM) It is designed to be as small as possible and still be able to accommodate the airflow/exhaust coming off the engine. When airflow is increased artificially on stock exhaust it can actually work against the horsepower gains "incurred" with the K&N air filter by reducing the ability of the stock exhaust to move exhaust on and out. Its very similar to the water hose analogy -- take a 1/2" garden hose and hook it up to your spicket at full blast (where the hose is at maximum capacity). Then hook the same hose up to a Fire Hydrant. Its ability to move water hasn't changed because the "force" behind it (in the case of my analogy exhaust = water pressure) has increased, it is the same and the pressure inside the Hydrant is what is adversely affected.

So for those of you who have a full aftermarket exhaust setup, from the headers back, AND a K&N, more power to ya' brothers. (Literally vroooooooom). For those of you who just have a K&N with stock exhaust and can "feel the difference" I would promulgate it is just in your head, and your filter does nothing more than let addition contaminants into your engine that shouldn't be there. That being said -- it is your car, and you can do with it what you please -- just be fully informed before you start mocking other members who are exactly on the money.

pcy

vk535i

Just installed the filter ... Don't see must different but I will keep it there for awhile

pjinca

Get the RPI scoop from Trinity Autosport (members Nerweezy or Trinityautosport) as well and you will feel a difference, especially when making a pass on the freeway. At freeways speeds you will feel better acceleration.

darkrider

I took the time to do my homework before making any performance mods to my 535i, and truthfully, you're not going to see huge performance increases with a drop-in filter on the N54 platform. There are plenty of dyno graphs over at N54tech.com to show that the stock airbox on the N54 is overly restrictive, even with the stock exhaust. On the N55's, it's not as bad, unless you move to a larger aftermarket turbo. That said, the RPI scoop will help some on a 535i, but Dual Cone Intake (DCI) will net you the most performance gains, especially in higher boost scenarios and if you're running JB+, JB4 or a Cobb tune. There are some naysayers regarding heatsoak with DCIs, but the tests Terry Burger has run and posted results for confirm that the extra air more than offsets the increased intake temps. However, for those who prefer a closed setup, you can search for the Mr5 airbox mod as it has netted some good results as well. I would recommend anyone looking for performance upgrades on the N54 to start with a tune, then do the airbox, followed by downpipes. Beyond downpipes, their are minimal performance gains to be had with the remainder of the exhaust, other than weight savings, unless you're running meth and/or aftermarket turbos. The tuners love the N54, because 100+hp gains are easily within reach for well under $1k, and the good news is that the drivetrain is more than up to the test!

Booyaazaa

+1

Heatsoak is not an issue for N54 engines since we have a IC to bring down the charged air temp.

AchtungE60

Wow. I bet you blame others for short comings in your life. I am happy you have complete confidence in BMW Engineers. However, as time will show with your car or just doing research,... there are many things that have been overlooked. I am sure they have customers in mind. They're not in business to do anything besides generate income.

I have been using K&N in all of bimmers (currently own 3) and have owned around 7 or so. I never had an issue. Using your logic, don't you think they would have been better to use metal fins vs. plastic in the water pump? In fact most of these cars are plastic!

paran

It's simple dude. You choose to allow more dirt into your combustion chamber than the OEM guys are willing to allow. That's it.

Having recently completed an O2 sensor job, I can see how that extra dirt could evenutally clog the pre-cats, intake silencer, catalytic converter, etc. sooner than with a OEM air filter.

But that's the trade-off for obtaining greater air flow. No need to get nasty about it.

JWMich

It's simple dude. It's all part of the bigger picture you can't see, you just don't have the ability to open your mind and you don't get the blissful path of the holy. Water pump, coolant expansion tank, chain rail guides, outside door handles, window regulators - all for your own good, to guide you toward righteousness. Do not question the way of the believer.

darkrider

Paran, just to be sure i'm getting my details right... You bought an off warranty E60 5'er with no extended warranty and a K&N filter installed. You're now completing a series of repairs and/or preventative maintenance to your ride. Are you convinced the K&N is to blame for those repairs? There are plenty of folks running aftermarket filters for 100K or more that haven't had a single problem beyond routine maintenance. There's not even a correlation between the two, much less a clear linkage to causation. As someone previously pointed out, where are all of these damaged cars?

I don't disagree with your notion that more minute particles are getting through an oiled cotton filter than a paper filter (mostly in the below 5 micron range). However, if a particle is literally so tiny that it's not causing harm to the engine or any other components, what benefit is there to the extra filtration given by a paper filter that is no more effective at removing the damaging particles (15 microns and above)? Basically you are just running the risk of starving your engine of much needed air and reducing power for a perceived versus real benefit! I understand your caution, and in the case of the diesel truck forum guys who based their opinion on little perceived performance gain, I don't see a problem in being extra cautious, as there is no real performance benefit. However, ask the same question in a sports car forum, and you're going to get an entirely different answer! Although our 5'ers aren't full on sports cars, they are about as sporty as you'll get in a sedan!