i have another thread going but since its sort of steered slightly off the original question, i thought i'd start a new one as a question...

I just picked up a K&N air filter and wanted to see what you all run on your boxsters and caymans... stock? K&N replacement? some brand's CAI? thanks

 

OEM.

I've used K&N's in the past but I just don't think they offer any benefit. Given the price difference, they're hard to justify.

 

hmm... how much does OEM run you? where do you buy it from?

 

OEM Mahle currently. I used to have a K & N in until it made my MAF go bad. The car was a bit throatier on the intake with the K & N but not worth the price of a new MAF.

 

hmm... was that the factory oiled one or did you attempt oiling it yourself before the MAF went up? I already bought it so if the factory K&N is fine, then I'll run it until spring then switch to OEM, but I don't want to risk it if its going to be a problem....

 

$22.

A person can shop around and find them at a number of places, I'm sure, but I like Pelican Parts:
http://www.pelicanparts.com/catalog/...BASflt_pg1.htm

 

I would NEVER put an oiled filter in my cars .

Oiled filters have at most an efficiency of 15 - 20 % (that's a lot worse than your average 1" thick Home furnace filter ) and then get progressivey worse, as the oiled surfaces get coated and can no longer hold the dirt particles.
They also should not be used in cold weather ,or when it's raining .

Read the big WARNING on the K&N filters , and HEED them .

Not exactly a good recommendation for a daily driver, and certainly not worth the 2 or 3 HP you get .

The OEM pleated filters on the other hand start at ~ 85 % efficiency and get BETTER , the dirtier they get .

Oiled filters are OK to use on a race car, where the engines are re-built after every few races, but are not suitable for a daily driver (at least not if you don't want engine sludge and plan to keep the car for a few years) Lol

 

Uh, what kind of data do you have to back this up?

If the OEM filter efficiency increases as it gets dirtier than you should never have to change it.

 

An oiled filter works on the "impingement" principle.
That means , as the air passes thru the filter, the dirt particles in the air, being heavier , tend to go in a straighter line than the air molecules and sooner or later hit a side of the filter .The larger particles, hopefully stick to the oil under the right conditions ,the smaller particles go right thru it and in time cause something called " oil sludge"
( you may want to read about what happens when THAT stuff builds up in
your engine ) Lol

Once the oil on the surfaces is covered with dirt , no more dirt sticks to it and it goes right into the engine.
That's why they must be washed and recoated with fresh oil periodically .

When it gets cold outside, the oil viscosity changes and the dirt does not stick to it as well as it should .
Last, when the outside air is moist ( when it rains ) the water particles which contain dirt, "roll off " the oiled surfaces and again, the dirt winds up in the engine(oil and water don't mix)


The OEM filter on the other hand is a pleated type , where the dirt particles get trapped within the fibers of the filter .
The dirtier it gets, the smaller the passages between the fibers become ,
even less dirt gets thru and the more "efficient" the filter gets.

Naturally, there comes a point where the pressure drop thru the filter gets to a point where the engine has to suck harder to get the air into the engine and the filter needs to be changed.

Does that answer your question ?

 

No, in fact I think it sounds even dumber now. Any idiot would understand that the filtered surface area would diminish as dirt collects in the filter media. How could you possible claim the filter to increase in efficiency as its filtered area decreases?

I think your idea about the K&N is equally suspect. Surely you have some 3rd party source you could site?

 

Alright I took your advice and did some research. Seems like the viscous impingement filter is ok for larger particles but I did not verify that it is less effective in varying temperatures or in rainy conditions.

The Barrier filter can filter smaller particles but most certainly does not increase in efficiency as it get dirtier.

 

Pulled from MNboxster on 986forum.com

http://www.billswebspace.com/AirFilterTest.htm

 

Thanks that was great. I have definetly been one of the guys saying "I have been using it for years without problems" . I have done before and after dynos and have seen gains but always with a CAI system never just a drop in.

Very interesting. I still think I will run one though.

 

A filter consists of millions of strands of fibers .
Air , containing dirt particles passes between these fibers.
The dirt particles which are larger than the spaces
between the fiber strands get caught , the smaller ones pass thru
and wind up in the engine
(that's the IN-efficiency of the filter)

As the spaces between the fibers get smaller due to the trapped particles,
ever smaller particles get caught .
Hence , the efficiency of the filter gets better, the smaller the
passages become.

I thought any idiot would be able to understand that ,
but apparently I was mistaken.

I'm not here to argue with you .
I don't sell filters and I don't buy used cars .
So I really could not care less what kind of filter you put into your car .

 

This is not true. Not arguing either but this is idiotic. At least I took the time to check it out, maybe you should do the same.