I have to disagree with you on this one. Each persone buys a Merc for various reasons. Some for the comfort, some for the engineering, others just because it has a star on the hood. If they believe something is better for them and their car, good for them. You don't have to agree.

More air into the engine will equal more power. Plug your filter and see how much power you loose. To determine if a standard pleated air filter is restrictive, air pressure would have to be measured after the filter. Ideally, there will be no measurable drop between atmospheric and post filter measurement. If there is no measurable drop under full load, there would be no benefit to a K+N. If there is a drop, you are loosing power. How much is anyones guess. Run you engine without an air filter (testing purposes only). This is as much air flow as any filter could ever deliver.

I originally asked the question because I do have a life and really can't justify spending the time to measure my air filter restriction. If I searched instead, think of all the bickering we would have missed! Hey, did someone mention WVO...

it's a proven fact that you get better airflow with a K&N filter than the stock air filter. anyone who disagrees just doesn't want to believe the science

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Somewhere buried in the threads there is a post where one member put a car on an Dyno and tested the stock filter, K&N filter and no filter. But, I do not even remember if it was a Mercedes. But, I do remember the K&N deliverd no more power at the wheels.

What I find interesting is that with Air Filters they give a cubic feet perminute spec on their filters but almost never give a filtration level in Microns.
The 3 that I could find listed Nominal 15 Microns and were not Mercedes Filters.

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84 300D, 82 Volvo 244Gl Diesel

testing on a dyno is not the be-all-and-end-all. you're hardly getting airflow at a standstill with a large fan blowing into your engine. you can't simulate the effect of airflow on a dyno unless the dyno is in a wind tunnel.

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Zero. Fuel makes power on diesels. If you need more air, turn up the boost.

Yes, but the big factor is that the stock air filter already provides more air than the engine needs, especially on the older engines. Think of it this way, I have a cup I want to fill with water, only so much water can get into the cup. One one hand, I use a pitcher to fill the cup, on the other, I use a barrel to fill the cup. Either way, the cup can only hold so much water and exactly the same result is achieved. The size and volume of the pitcher and barrel have no relevance on the set in stone size and volume of the cup.

When people put an ebay "cold air intake" on their diesel, the only difference in performance that is realized is a nice audible turbo whine, otherwise the engine is taking in the same amount of air. I did this, apart from the turbo whine, the engine was no different.

Its not a matter of the K&N providing more airflow and thus more power, its a matter of the K&N doing nothing substantially more since the engine already gets far more air flow than needed from the stock setup. Thats why its not a great mod alone on a stock engine, regardless of the flow differences between paper and K&N gauze and whether or not you think one is damaging.

I have one of those round K&N OEM replacement filters on my 240 now, which came with the car, but I am switching back to paper since I think its just a pain to clean out the gauze filter. Id rather just slam in a paper element in the 40 seconds it takes to unbolt one bolt and pop 4 clasps.

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This post brought to you by Carl's Jr.

Yes but the only affect your K&N is having is to allow more dirt in. Again the stock filtration system is over engineered for its needs, atleast on the 617.95x. I can only assume the same is for all the mercedes diesels. I have used K&N on my 85 and I switched back to paper.

If you want to get rid of the crappy air filter mounts, keep filtration up AND flow more air this is one of the better solutions (I use this now).

http://www.superturbodiesel.com/std/attachment.php?aid=2768

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http://superturbodiesel.com/images/sig.04.10.jpg
1995 E420 Schwarz
1995 E300 Weiss
#1987 300D Sturmmachine
#1991 300D Nearly Perfect
#1994 E320 Cabriolet
#1995 E320 Touring
#1985 300D Sedan
OBK #42

My stock setup starts to open the wastegate around 2000rpm at full throttle, indicating that it is getting more air than the engine is designed to handle. It remains open to the high-rpm limit. I base this on the boost gauge being at max. boost in this RPM range. More air would equal more wastegate dump. Any questions?

On my first (Caterpillar) diesel motorcoach, it was an NA, so more air meant better power and mileage, I did some serious re-design on the air intake and filtration to gain power/mileage/cooling/cleaner exhaust and could measure the results.

In my opinion, it is possible that the NA engines might benefit slightly from better airflow, but there is no data available to show that there is better airflow from the K&N in these cars and resultant power/efficiency increases. There is a lot of concern about the filtration efficiency of the K&N, and little/no data available to alleviate these concerns.

If the data exists to show a difference in filter restriction, and a resultant improvement in engine performance, I haven't seen it. I will happily read it if it does exist (real data with verifiable results) as would many here, those would be the real facts as would filtration efficiency graphs and numbers (which I haven't been able to find either).

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Gone to the dark side

- Jeff

It benefits the manufacturer and it's employees. That's about all.

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Michael LaFleur

'05 E320 CDI - 86,000 miles
'86 300SDL - 360,000 miles
'85 300SD - 150,000 miles (sold)
'89 190D - 120,000 miles (sold)
'85 300SD - 317,000 miles (sold)
'98 ML320 - 270,000 miles (sold)
'75 300D - 170,000 miles (sold)
'83 Harley Davidson FLTC (Broken again) :-(
'61 Plymouth Valiant - 60k mikes
2004 Papillon (Oliver)
2005 Tzitzu (Griffon)
2009 Welsh Corgi (Buba)

I kind of doubt if there is much of an effect due to andy sort of Air being rammed into the little Plastic Air Inlet tha squeezes between the Hood and the frame in front of the Radiator.
In fact the opening looks very restrictive.

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84 300D, 82 Volvo 244Gl Diesel

"Very restrictive" is a relative term, if its enough then its enough and theres no advantage to more...

I had a K&N in my '96 Dakota v8 for years, I played with switching it back and forth with a paper filter, even had a friend randomly switch it so I could measure mileage and "feel" without knowing which filter I had. I never could detect ANY difference either in mileage or how the engine felt. I sold that truck with 222,000 miles because the transmission was going, the engine still ran just fine. I gave up on the K&N at ~150,000 miles because as other posters noted I thought cleaning the filter was more work than it was worth.

So my conclusion is there is no advantage in a K&N filter, nor do I think it will "destroy your engine" in any reasonably short time frame. As others have said the real advantage is to those who make and sell the K&N filters.

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Sadly Benz-less

every now & again there is a turbo/supercharger thing on ebay. Its a fan that goes on the air inlet. Every one knows they are junk & dont do any good & only a ###### would get one. They, like the K&H claim increase air flow & so hp.
Here in Australia we have a 4wd called the Mitsubishi Pejero, I think its known as Montero or Shogun in other parts of the world. I suggest you all look it up on wiki & find out why its not called pejero in Spanish speaking countries, because maybe thats what has been going on with the K&H discussion !!

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Grumpy Old Diesel Owners Club group

I no longer question authority, I annoy authority. More effect, less effort....

1967 230-6 auto parts car. rust bucket.
1980 300D now parts car 800k miles
1984 300D 500k miles
1987 250td 160k miles English import
2001 jeep turbo diesel 130k miles
1998 jeep tdi ~ followed me home. Needs a turbo.
1968 Ford F750 truck. 6-354 diesel conversion.
Other toys ~J.D.,Cat & GM ~ mainly earth moving

Its also a fact that a turbodiesel has far more air than it needs. Hence the wastegate on the turbo. The stock air cleaner and filter can flow far more air than needed. This is the exact reason a K&N is pointless. MB did know what they were doing when they engineered the air intake, believe it or not.

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-diesel is not just a fuel, its a way of life-
'15 GLK250 Bluetec 118k - mine - (OC-123,800)
'17 Metris(VITO!) - 37k - wifes (OC-41k)
'09 Sprinter 3500 Winnebago View - 62k (OC - 67k)
'13 ML350 Bluetec - 95k - dad's (OC-98k)
'01 SL500 - 103k(km) - dad's (OC-110,000km)
'16 E400 4matic Sedan - 148k - Brothers (OC-155k)

The only thing a less restrictive filter will do on a turbodiesel is reduce the pressure ratio the turbo has to work to make. That means less exhaust manifold pressure is needed to make the same boost and, as noted above, the wastegate will be open more.

The result; no change in airflow through the engine and an immeasurable power difference from the reduced drive pressure (well within any dyno session's environmental margin of error). The "power" people "feel" from installing those little cold air / short ram intakes is just noise since the muffling effect of that 180* tube is gone.