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Discussion Starter #1
I just did a search looking for any discussions about the downside to installing an air filter other than the OE filter. Didn't really find any. The overwhelming majority of opinion on other Mercedes forums that I've been on is that the K&N filter is not good for your engine. In a diesel there is more air than the engine can handle using the OE filter anyway. On Mercedes with MAF's, the oil from the K&N can knock out your MAF and in all Mercedes, more air flow equals more dirt getting through to your engine. So are all of these negatives applicable to the SLK? I would tend to think that they are.

The green filter I don't know much about, but would be willing to to listen to comments and would especially like to see some lab reports. I still think that more air flow would equal more dirt getting to your engine.

Len
 

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Administrator 2009 SLK 55 AMG/Founding Member 2006
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Discussion Starter #3
Jeff - I did that exact same search and that's what prompted my question. Much pro as you say, but nearly all are things like "it feels so much peppier", etc. Replacing the dirty OE filter with a new OE filter would give you that same feel. How it feels isn't what I'm after. It's facts that I'm after. :)
New OE vs. new green. Labs test OE vs. green. I'm not about to put one on my car just based on a few folks "liking" it.

Len
 

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A lot of bull talked about these cloth filters imo. I have k&n and it works ok, equally save your cash and stick to OEM, once these are dirty Im going back as its not worth the effort to clean them. Your wrong about more airflow = more dirt passing through.
 

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Guy did a study on a BMW K-series motorcycle.

Found no difference in power output comparing ...

  • OE filter and no filter at all
  • K&N filter and OE filter
See http://www.ibmwr.org/ktech/dyno/index.shtml

The R171 SLK system, then would have to be pretty restrictive and it's hard to see how it would be, given it's split into two filters. If it is restrictive, it would have to be due to the air intake and/or airbox design rather than the filters themselves, and given that it's split into two sides, hard to understand how this could be.

So seldom mentioned in K&N discussions is the fact these filters are of very low quality and often times not really the correct size for the car they're ostensibly designed for. That is, when it's a round filter around a carburetor, dimensions don't make so much difference, but when it's a rectangular filter designed to fit tightly in an airbox, they do. Photos have been previously posted at MBCA forum showing K&N filters that have collapsed into the airbox.

IMHO it's amazing how some "testing" probably left over from the 1950s done on probably a Ford flathead has supposedly become gospel in the automotive world. The notion that a manufacturer such as Mercedes skimps on intake designs, doesn't test them, or whatever, is pretty ridiculous.

One might also consider the existence of uber-sports cars such as Mercedes SLR, Mercedes SLS, Bugatti, Aston Martin, Ferrari, etc.--none of these are fitting anything but normal paper airfilters (more to the point, they're not fitting K&N), although the price of these supercars could easily absorb the "extra cost" of supposedly superior filtration.

And, it's correct, not only is it not superior filtration, it's poor quality and will indeed mess with MAF sensors, and damage caused thereby will be paid for by you and not your warranty.

Just say no.
 

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i used a TRD filter(similar to K&N or Green) in my Toyota Tundra for a while. With it, the engine made a lot more noise but gas mileage didn't change and I doubt it ran any better. It was a PITA to clean and re-oil and, after doing so, I got a little too much oil in it and it fouled my MAF. Cleaned MAF and tossed the filter. I now stick with OEM. No more troubles.
 

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I look at the air intake opening for the airbox for the filter and wonder if it was larger would that improve perforance. On a 2001 SLK 230, it is a small neck that runs to the front behind the grill that is about 2 inches in size. My thinking filter can only filter the amount of air that gets to it. More air to the filter more air for the engine. Has anyone tried to increase this opening and what was the results.
 

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I look at the air intake opening for the airbox for the filter and wonder if it was larger would that improve perforance.
No offense, but unless you're an engineer, looking at something and concluding it's small is not particularly scientific nor likely to be accurate.

Safer to assume (and be correct) that the actual engineers that actually designed the system made it plently "large" enough. It's a Mercedes, a German car well capable of flat out Autobahn running. There aren't many $50 fixes left.
 

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I just replace my OEM filter much more regularly than called for by Mercedes. I do notice a slight difference when I put in a new OEM after say 20,000 miles or 2 years.
 

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I think the airbox needs to be als small als possibel. you engine creats a vacuum to pul air in. If the airbox is big in size the engine needs to create a lot more vacuum to get fresh cold air inside. And is you ever weard a gas mask you know howe bigger the space in de mask the harder it is to breath in cleand air truh the filter.

Maybe i got it wrong :)
 

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Over the years there have been several studies, test (scientific and non), and articles exploring the efficacy of non-OEM air and oil filters. None of them have had any conclusive results and have generally deteriorated into mindless mumbo jumbo.

Why anyone would waste their time on this nonsense is beyond me. The mfg clearly spells out the proper filter for his product, and he certainly isn't going to recommend something inferior. In the case of MB, I believe Mann is the recommended replacement (OEM too I believe?).

What's interesting, if there is anything interesting about this subject, is the OEM filters are quite reasonably priced while the posers are often more expensive. You can get your filters and many other SLK parts from Amazon.com and free shipping. Order a case or two today!
 

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Why anyone would waste their time on this nonsense is beyond me. The mfg clearly spells out the proper filter for his product, and he certainly isn't going to recommend something inferior. In the case of MB, I believe Mann is the recommended replacement (OEM too I believe?).
Except for the fact that the EPA has created emission standards that have forced manufactures to decrease performance. Few have a cold or forced air intake. Often there are bends and boxes that reduce airflow, why would the filter be any different? :confused:
 

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Except for the fact that the EPA has created emission standards that have forced manufactures to decrease performance. Few have a cold or forced air intake. Often there are bends and boxes that reduce airflow, why would the filter be any different? :confused:
Every Mercedes there is has a cold air intake from the factory.
 

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I posted this on 09/06/09:

"...But looking at the air box and OEM filters, it is very obvious why there is more power and a deeper, richer sound with the greens. The OEM filter almost block off the air intake, the incoming air hits the filter pleads ‘side’ edge on, creating very high resistance to flow. The greens are relatively thin, allowing the air to easily disperse under the filter and take advantage of the low restriction filter medium..."
 

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Premium 2006 SLK55 AMG (Kleemann K2)
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I replaced my Green filters for the oems for the time being, as I've got a new pair of Green filters on the way ( been using Greens for 4 years now); My car doesnt pull as strongly as it used to.

If I wanted to use Green filters as an example, think of it as a nice subtle ingredient to your gourmet meal that makes a difference Ie fennel or lemon.

I hope it makes sense :)
 

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.....My car doesnt pull as strongly as it used to. .....
You mean it doesn't pull as strongly with the OEM paper filter?
 

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Discussion Starter #17
If I wanted to use Green filters as an example, think of it as a nice subtle ingredient to your gourmet meal that makes a difference Ie fennel or lemon.

I hope it makes sense :)
You may want the fennel or lemon getting through to your gourmet meal, but you don't want it getting through to your engine. :)

Len
 

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Yeah -sure!

I posted this on 09/06/09:

"...But looking at the air box and OEM filters, it is very obvious why there is more power and a deeper, richer sound with the greens. The OEM filter almost block off the air intake, the incoming air hits the filter pleads ‘side’ edge on, creating very high resistance to flow. The greens are relatively thin, allowing the air to easily disperse under the filter and take advantage of the low restriction filter medium..."
This is exactly what I mean. This is convoluted hyperbole which is meaningless.

There have been numerous dyno runs on many engine comparing the hp/torque of OEM Vs aftermarket. Not one showed the aftermarket a better choice. In fact, there was evidence that air filters like K&N allowed more dirt to enter the engine.

However, to be fair, there has never been a study to my knowledge that settled the matter. I do remember a study of oil filter done by some guy who thought he was using scientific principles to demonstrated that some filters were better than others. The problem was he just disassembled them and then speculated about their properties.

Companies that sell these aftermarket filters don't really provide any objective evidence that their products are better than the OEM. Essentially their claims of superior performance are just marketing statements without any real facts to back them up.

Also one final note to air filters. People who install the K&N air filters say they like the sound or tone it makes. Somehow they equate this to an increase in power. In fact, they get indignant when anyone challenges this. I figure you'd get even better sound from the intake poking holes in or eliminating the filter. :rb
 
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