[W126 Coupe] K&N Air Filters

[Gerry Van Zandt]

There are very mixed opinions with regard to K&Ns.  Some people swear  
BY them, and other people swear AT them.

If you use them, it is CRITICAL that they be oiled at appropriate  
intervals, and they must be oiled correctly.  Too much oil is bad,  
particularly on newer cars with hot wire or hot-film (LH or HFM)  
intakes (M119 and M104 engines, for example).  Too much oil will gum  
up and eventually destroy these sensitive components which otherwise  
last quite a long time.

On older cars such as the coupes with the K- and KE-Jet intakes, this  
may not be such a factor, but too much oil on the filter elements is  
still NOT a good thing.

I've seen lots of statistics with regard to K&N filtration being  
superior or average (on par with stock paper filters).  It's similar  
to the "oil type" debates -- lots of pro and con reports.  Personally  
I'm a proponent of just using stock / paper filters, as the factory  
specifies, on all my cars.


Interestingly, I just received the latest MBCA STAR magazine in the  
mail yesterday.  Looking through it this morning, just 30 minutes ago,  
I saw a report by MBCA Tech guru George Murphy about his recent  
purchase of a 1999 C43 AMG sedan.  I quote from the article:

"The only flaw [with the car] I discovered was that the owner had  
installed oil-wetted K&N engine air filters about 5,000 miles ago. So  
I brought along two new M-B OEM air filters to replace the K&Ns before  
the 500-mile trip back to Tennesee. When I opened up the air filter  
housing to remove the K&N filters, the housing showed considerable oil  
accumulation from the oil-wetted K&N filters.

This was probably the cause for the slight hesitation on acceleration  
that I detected when I first drove the car. The oil from these types  
of air filters can foul the engine's Mass Air Flow (MAF) sensor,  
eventually causing failure of that sensor. The K&N filters did not fit  
the OEM housing very tightly either, allowing unfiltered air to enter  
the MAF sensor, which could eventually ruin this expensive part.

...

Subsequent fuel mileage calculations show about 21 mpg in mixed city/ 
highway driving. I feel that swapping the K&N air filters for correct  
M-B parts greatly improved drivability and fuel mileage. The new  
filters apparently fed clean air into the MAF and reversed the  
degradation caused by the oil from the K&N filters, thereby improving  
performance."

Cheers,
Gerry



On Jul 12, 2008, at 9:15 AM, mbcoupes-request at mbcoupes.com wrote:


> Hi all,

>

> Just wondered if many on the group have had experience with K&N  

> filters. I just recently purchased one for my 91 560 SEC Euro. I  

> didn't get it for all the claims for more horsepower and all that  

> hype, I got it just because it never needs replacing again. But I  

> could swear that I don't quite have the ZZZZIP from a kickdown to  

> first that I used to have. In fact I would say there seems a  

> fraction of a second delay when flooring the accelerator in  

> comparison to when I had the stock filter. I haven't scientifically  

> timed the difference, but it seems like the K&N filters are more  

> restrictive to the airflow than stock. As these K&N supposed to be  

> less restrictive, I was wondering if you get this at first because  

> the oil in the filter straight out of the packet and if it becomes  

> less restrictive to air after it has dried out a bit, after say X  

> amount of miles have been put on it. Hoping my last sentence is  

> closer to the truth. Look forward to your comments.

>

> Regards,

>

> Vance.