A recent thread on this forum discussed oil bath filters and the benefits of aftermarket, cloth and oil filters such as the ubiquitous K&N. From that thread I really liked and appreciated tracks914’s oil bath filter housing conversion to paper. I noticed his was the final post in that thread so I wish to say: “thanks, tracks914 and congratulations on your 1,000 post” (member #163)!
http://www.914world.com/bbs2/index.php?s=&...st&p=426851

Many believe a legend that “when the German engineers tested various air filtration methods they were surprised to find that the air vortex formed by oil bath filters created a superior filtration effect”

Sometimes legends are true and I’m sure that at one time oil filters were better than the alternative. VW beetles didn’t have oil filters (did Superbeatles?) so I’m not sure air filtration was that important for those cars. Some people say that so long as the oil bath filter is engineered to match the capacity of the motor it will work well, but there is the convenience factor. If that is the only diff. I have to wonder how many big, expensive stationary engines, e.g., generators, pumps, lifts, use oil bath air filtration? (I don’t know the answer)

Anecdotal evidence abounds for either position. I own two 40 + year old tractors with similar hours. The one with an oil bath filter has low oil pressure and low compression -- these are obviously symptoms of engine wear. The other one uses a paper filter. It has high compression and good oil pressure. On the other hand I don’t know how either tractor was used during their first 2000 hours of run-time.

There is a general agreement that oil bath filters are by design somewhat more restrictive than most paper element filters. The debate is over their effectiveness at filtration. Put another way, would another filter of reasonable size outperform the oil bath filters that were OEM on certain cars and tractors in the past? What about “performance” filters like K&N. Are they adequate?

Today the filtration effect on particles can be measured by the millionth of an inch; however, the most accessible study on air cleaner types relied on a visual comparison to draw a conclusion that oil on cotton and oil on foam are inferior to paper elements, and that of a half dozen filters tested, K&N allowed the most pass-through dirt.

Bob Is the Oil Guy: http://www.bobistheoilguy.com/airfilter/airtest1.htm

On another Bob is the Oil Guy thread there is discussion of an often referenced study that declared the superiority of oil on foam, oil bath, and paper filters when compared to oil on cotton.

Amazingly, the publisher of that study was a member of that forum and when pressed made the following comments:
“Never say anything on the internet, it will haunt you forever. 

“Here is a link to the original posting: [url=http://www.roadkill.com/~davet/moto/air.filters.html[/url]
“We didn't do the tests. The data came to me from an ex-GM engineer that was working on an emission study with us. I don't know where the original data came from. It's at least 20 years old, and the engineer moved on a long time ago.

“Advances in paper media have certainly improved the performance of paper filters. I still would choose an oiled foam above a K&N, and paper above both. I don't think the oiled foam are really as good as shown in the chart, based on experience.

“I think the design of the oil bath does have a lot to do with it, as does the weight of oil used and the ambient temperature. The one on my John Deere has a relatively shallow oil pan and a tall coarse "steel wool" element. It doesn't appear to be terribly restrictive. It's certainly kept the old beast alive for 69 years of working in dusty fields.

Ed”

A French language study compared the dirt grabbing properties of oil on cotton and OEM paper filter. The K&N “caught” 97% of the particles while the OEM Honda was 99% percent efficient.
http://www.motovationusa.com/230-FiLTER.pdf

A fellow with an oil bath filtered tractor performed an experiment, where he carefully cleaned the filter and changed the oil on his tractor, ran the tractor for a time and sent an oil sample to be analyzed: The report indicated excessive “wear metals” indicating “high silicon” which is sand.

#1806417 - 03/06/10 06:17 PM
 Re: Oil bath air cleaners [Re: Seguino]
widman 

I am not drawing conclusions from any of this other than the issue is not settled. I will say that my oil filter housing leaks and got oil all over my engine last time I tried to use it.

I also believe the OEM air cleaner housing serves additional important functions as a heat shield and air turbulence controller and that the lack of these can be a problem if you replace it with a bare cone filter. I've experienced this effect first-hand with motorcycles.

I'm going for a tracks914 conversion.


Stuart

Great summary! Thanks

Yes VW Beetles did come with oil bath air filters , I have an original 71 1600 DP OB air filter housing left over from the bug I owned years ago.Early ( 50's )GM, Ford etc came with oil bath air filters. One of the problems with oil bath filters is hard cornering can slosh oil up into the screen media and sometimes chock the carb some. I do perfer the paper element for the filtering capabilities and the ease of maintence .Others have thier thoughts also........

Jack

The common reasoning to "upgrade" from paper to oiled cotton or foam is increase air flow/reduced restriction and increased intake sound. Many don't consider the effect on filtering a change in media will make. Some will not care since the primary concern is performance and engine life is considered expendable.

Of course whether or not the oiled foam and/or cotton filters give an increase in performance is debatable as well.

I was brought a 93 Audi S4 that had just had big turbo, RS exhaust manifold, TAP chip, larger intercooler and K&N filter "upgrade". The car was fast, seriously fast but if you stomped on it in 3rd gear it would wind up really fast come up on boost really well and then set the "Check Engine" light and go in to limp mode. If you shut it off it would reset and was fine until you really wound it up in 3rd again. The code set was for overboost but the boost pressures measure by gauges and the ECU were below the level to set this code. Some research turn up the code was a calculated over boost not measured over boost. The sudden build up of boost in third pulled in so much air so fast the air turbulence thru the MAF confused the MAF reading and the ECU determined too much air was going in for the RPM and the boost pressure must be too high and shut everything down. Putting the stock air cleaner housing an filter element back in smoothed out the air flow and no more "Check Engine" light and limp mode.
When ever you make a modification to your car you are changing something an engineer or team of engineers planned and thought out and it may not work out as you would expect.
That said my 2.0L engine has the stock housing with a stock paper filter but I have a custom made velocity stack with a K&N filter that mounts directly to the throttle body for those times I want to go a bit faster (or at least think I am going faster)

Jim