alan_e550

Hi everyone,

I'm planning on having the secondary cats removed in place of straight pipes as well as having my resonator removed in place of an x-pipe on my 2011 e550 4m. I was talking to a Mercedes-Benz technician and he recommended using K&N high air flow filters once the exhaust mods are done. I've read that the only reason why these filters are "high air flow" is because they do less filtering. I was originally just planning on buying a new set of Mann filters (OEM equivalent just without the MB logo). Are these filters really worth it and could they potentially harm my engine?

pierrejoliat

K&N air filters were originally designed for dirt bikes, so they could be cleaned after use, if you ever used a target saw on concrete or rode a dirt bike all day in the dry, you may have seen a pleated filter that was smooth on the outside from all the dust.
Paper filters do a better job of filtering everything, especially small particles, oiled filters flow more air because they filter less, this is not so important on a target saw or dirt bike because you want them to keep going and not foul out or lose power. The stock air filters were designed to do their job, some for 20k miles, the K&N will last longer, provide more airflow and allow some smaller particles to get through, we are however talking in microns. both are good choices, change the paper filter every 20k or wash out the K&N every 10k. The oil s not too expensive. I use both and am happy with the results and accepting of the limitations. I never noticed any difference in performance,

rapidoxidation

Hold a k&n air filter between you and the Sun. See all that sunlight coming through? Do you really want rocks that size being breathed into your engine? I don't. Full disclosure, I used to have a k&n filter on my 1996 Chevy diesel pickup. Each time I cleaned the filter, I also had to clean the downstream ("filtered") side of the air intake because it was coated with dust. Close tolerance moving parts don't like dust.

High quality disposable filters for the win.

diesel_dan

I've only used K&N on a track car. I would only use them on one of my dirt bikes with several filter skins over the filter - check that, there are better dual density washable foam filters, so I wouldn't even use the K&N there. If you were to take a clean and properly oiled K&N, or any of the gauze-style oiled filters, outside and put it up to the sky so the sunlight shines through, you'll understand where the airflow is coming from. Be aware that any oiled filter can mess with your airflow sensors, and if they are the cone style filter sitting in the engine bay, you have just changed a nicely designed stock cold air intake into a hot air intake.

On a couple of diesel truck forums I'm on, newb's often will put these type of filters on thinking they are improving airflow. Then they get what we call there: "dusting" the turbo - enough large particles of dirt are getting past these type filters to where the blades on the intake side of the turbos are eroded away with tons of small pits, eventually destroying the turbo...

I'm of the opinion, that like the Chevy, Ford and Dodge diesel engine designers, Mercedes over-designed the stock air cleaning system to handle way more air than the engine needs. What cracks me up is when people put "cold air intakes" on that actually are Hot Air intakes: ingesting heated engine bay air - which hurts performance...

My $.02

up_too_late

A K&N sticker alone is worth a 5HP gain, each.

DFWdude

We've discussed this topic on this forum and others more times than can be counted. The concensus in all cases is that K&N air filters are not worth the cardboard box they come in.

rapidoxidation

They're expensive but at least they're inefficient.

diesel_dan

Now that, made me Laugh Out Loud!

Dane500

That's hillarious.

I would not recommend an oiled filter with a maf sensor. Especially these new generation super sensitive ones. These (and most engines) are designed to run and last as advertised with what they have installed.

Left Coast Geek

put your car on a dyno with a dirty well-used stock air filter, get your dyno numbers. now, remove the air filters entirely, get more dyno numbers. now install brand new Mann or Mercedes OE filters, dyno one more time.

I predict all 3 sets of numbers will be within statistically equivalence.

nota_amg

if you're not going Blackboost, better off to just stick with the factory paper elements...

pierrejoliat

Well, the only thing I have ever dyno-ed is my Ducati, it makes 6 more horsepower without the air filter which is 4.4 % 4.4 is not "statistically equivalent" just sayin'

rapidoxidation

I can tell when my truck air filter is dirty: MPG drops by 1 or 2 (significant on a 16mpg engine) and coal starts rolling. A clean air filter will give grey smoke when I get on the go pedal. Can't speak to dyno results though.

Quattrodude

I really enjoy watching this guy - all his reviews are great

Enjoy this on air filters - this should answer your questions...


For me - Id rather have an engine that lasts longer than 10 more HP...

Cheers

Gazwould

He's not wrong !

But this will continue even with the upcoming young oiks putting a K&N sticker on an EV .


https://www.nicoclub.com/archives/kn-vs-oem-filter.html



.. "which investigated the high failure rates of modern MAF sensors. Several factors where involved which revealed what many have suspected all along.

Higher air flow capability with the K&N is the result of larger pores in the filter media to offset the smaller total area when compared to any OEM filter. Oil is used to help trap the dirt when it comes in contact with the filter media. One of the aspects of this design allows what is referred to as "Tracking" where certain regions of the filter media as a result of internal air box flow patterns directs particles to specific regions of the filter more than others. What occurs next is those regions lose the oil saturation to the increased dirt loading allowing particles in the 90 micron range to pass through the media since there is no longer any more residual oil in the local pores.

Oil migration. Oil migration occurs when the motor is in warm climates and/or operating at high engine speeds where the volume of air passing accross the filter carries small amounts of oil into the air stream post filter which is now entering the motor.

Particles less than 90 microns... Pull a hair out of your head and push it through the filter media, if it passes through you have a filter with pores GREATER than 100 Microns in size! This is the primary issue with MAF sensors. MAF sensors rely on filtration quality that captures 95% of all particles greater in size than 15 microns. Ideally 10 micron capability would result in longer life but now the physical size of the filter is increased to offset the fine fitlering capability when using conventional or synthetic fibers in an "Un-Oiled" air filter.






MAF air flow sensor design. MAF sensors use micrscopic heating elements placed on a circuit board. The heating element provides a constant rise in temperature to provide a known condition for the ECU to calculate air flow. On the leading edge of the MAF sensor is a temperature sensor which measures the temperature of the air passing over the leading edge, this temperature returns a value to the ECU. As the air passes over the heated portion of the MAF sensor heat is transmitted to the air stream thus heating it. As the air passes accross the back portion of the sensor a second temperature reading is taken. Higher flow rates result in lower temperature rise, lower flow rates result in higher temperature rises.

Another aspect of the MAF sensor is static build up on the leading edge of the sensor element. This static charge causes small particles of dirt and debris to adhere to the elements leading edge distorting the laminar flow characteristics of the sensor throwing off the temeperature readings take accross the elements surface. Over time rotors form accross the back side of the build up depositing oil, dirt and anything else that is in the slip stream directly onto the heating elements surface. What happens next is that the oil/dirt or any combination of the two insulates the heating element causing it to overheat and short out. The result is a complete loss of data to the ECU causing it to revert to default values stored as a limp home function.

The precursor to the failure is often a reduction in peformance as a result of inaccurate thermal readings accross the sensor plate. As the dirt accumulates power typically drops off until the heating element fails.
















OEM air filters believe it or not out perform K&N in all aspects. This is easily done by using filter media which has much smaller pore size (5 microns on "average") this allows typical filtration to hit the 10-15 micron range with the 95% effective range. However the fine filtration capabily results in more restriction, the restriction is offset by increasing the depth and number of the pleats the media uses. The biggest advantage to this is that the OEM filters are able to go 50,000-100,000 miles between changes WITHOUT resulting in any increases of restriction or worse yet ALLOWING MORE DIRT TO GET IN THE MOTOR! OEM filters REGARDLESS of miles or time in use perform as well or BETTER the more they are used again up until the reach the maximum restriction point (15" or 25" WC).

Most OEM air filters have anywhere between 1-4" water colum of restriction when new. A fitler is considered to be "Loaded" when restriction reaches 15" WC on naturally aspirated motors and 25"WC on turbo or supercharged vehicles. Regardless of how dirty the filter may look provided restriction does not exceed the above numbers the filter is providing 95% efficiency at removing all particles greater than 10-15 microns.

Bottom line is that using any type of high flow filter that does not meet the 95% filtering capability at 15 microns is asking for trouble.

Call K&N and ask them what their filtering efficiency is at 15 microns and if they will warranty the MAF if it becomes contaminated and burns out... I will save you the time, they will laugh at you and not do a thing."




I wonder what Lambourghini and Ferrari use....

Left Coast Geek

I dunno, but that test was full of wrong. their particle test, dumping flour or whatever directly on top of the filters? thats not how it works,, the dust is in the air going into the filter box. and I didn't even see them oil the K&N filter, are they selling those pre-oiled now?? the ones I've seen always came dry with a vial of the oil to spread before installing.

ygmn

Filters for cars today are not tested nor do they provide any proper specifications.

In the hydraulic world we have plenty of specs and terms to denote what filter is better.

Filters have:
Frame cross sectional area
Media Cross Sectional area (unfold the media)
Media material/type
Media pore size
Pressure drop thru filter system
Beta ratio! = Amount of dirt of a certain size the filter caught in a BETA TEST which tells you how to do it and is specific.

This applies to oil filters too..
And without the above info no one knows anything about the filter other then over oiling is a bad thing.

Point is we as consumers will never know as they keep this info hidden from the public.

For the same frame cross section area to filter MORE and Smaller dirt means MORE PRESSURE DROP across filter which means LESS AIR IN ENGINE.
For the same frame cross section area to filter LESS and larger dirt means LESS pressure drop across filter which means more air in engine.
So no FREE LUNCH

Ya want more air? get a larger Air filter and make a new filter box that flows better.


Now if you need a hydraulic filter they tell ya everything.

Dane500

Paper. I have seen many fouled mafs due to oiled "filters"....and angry owners claiming its the mafs fault.

Left Coast Geek

I bet Mercedes specs all that, but their specs are NDA between the OEM and Mercedes

btw, its not the filter box size, its the filter surface area. they are pleated to increase that surface area, by a lot.

ygmn

PRessure drop is based onbox size and surface area as I stated.
if you pleat it too much and jam in small box it can be solid... no?

Trust me I deal with filter engineers all the time in my job and they are geeky about filters.