OIL BATH velocity filter

[JohnEd]

I have heard the OB filter described as "very heavy", a PITA to clean and service, LARGE...etc.  I have never heard that it was "not effective" or even that paper was better.  In reading those posts I always wondered how often the things needed serviced.  I recall that the one on my VW was still not seriously full of dirt in the bottom of the oil resovoir after three years in the S. Ca. desert dusty environment.  I know that they need the air to be moving at a good clip to hurl the dust particles at the oil and thus trap them and have wondered if the filter might have been restrictive because of flow design.  Efficiency would be a great agrument except that I have been told by old bus derivers that the 8V71 with a 3 speed stick got 10MPG.  Don't know if that was true but it would seem that the oil bath didn't choke it off.  These guys were BP... as in "before paper".

OK Hit me!

JohnEd

[lostagain]

I have oil bath air cleaners in several older pieces of equipment I have as well as the bus, and they are not difficult to maintain. Take the bowl off, dump the oil, wipe clean the bowl, and fill with oil again. Can hard can this be? My question is: how effective are they compared to paper? And how restrictive (air flow wise). I'll find out when I put a Filter Minder gauge on mine.

[JohnEd]

Lostagain,

I liked that system, also.  I read up on them some a long time ago and I remember it said the air had to be moving pretty fast when the air flow turned the corner at the bottom of the filter so the smallest particles owuld get flung against the surface of the oil and get captured.  The part I didn't like was the need for speed.  The article said that going to a higher volume filter would cost you in filtering action.  Burried in there was the question of air velocity and airflow resistance.  Sure hope you give all of us a read when you do the "filter minder gauge" install.


Thank you

John

[tekebird]

considering the ammount of crap my oil bath filters grab you would have to change paper filters every 3000 miles or so.

thing that is nice about oil bath.......when they are working they do not cause loss of air flow like a working paper filter does.

as far as speed?  there are alot of off road type equip around still using oil bath....


and it doesn't take all that much RPM to make them work...........hold some tissue to your air intake at idle.....you'll be supprised

and better yet.........let your bus idel for a bit....then pull one of the screens.......check the amount of oil that has been sucked up into the screen

[NJT 5573]

lostagain, I think that the oil bath days are gone. My farm tractor still has one on it though and it has worked for years in severe dust without engine damage. I think it says to service it every 30 hours which is frequent. Some years ago I changed a NA250 cummins out for a NTC350 and the turbo would suck all of the oil out of the oil bath. Paper units are cheap new, about twice the cost of a new filter and an extremely wide variety of shapes and sizes are available used at truck bone yards. Air flow is very important and I have no recolection of seeing the oil unit with larger than 4in inlet/outlet. If you want her to run, get a big one, or even two.

[lostagain]

It will be a little while untill I'm ready to test the restriction in my oil bath filter. I'm waiting for a adaptor for manifold to turbo from the machine shop. Then I'll have to do the plumbing for intake and exhaust. I'm working at this project in my spare time, when it is not too cold out, because the coach is in a shelter, no heat. The other day I rented a fan and sucked about 1000 to 1200 CFM through it. It did not pull oil out of it. When it is mounted back into the bus, I will do the Filter Minder test and let you know. De Book says 20in of water max for the 4-71T. I'll go to a paper filter if I have to.
When I turn the fan on, I could see the oil level go down to below the bottom of the intake tube. So the air does not actually go through the oil. It makes a sharp upward turn and, according to the manual, it picks up some oil then goes up through the separator and mesh element...
My unit is the heavy duty type. 14" diameter, 20" high, 5.5" intake and 4" outlet.

[TomC]

Virtually all air cleaners now are dry-including the huge off road mining trucks.  Check out the Donaldson web site to see the really big air cleaners.  They even make a wall full of dry filters for gas turbines.  Good Luck, TomC

[tekebird]

I went to college with a guy who ended up being an engineer for Cat.........he told me that the oil bath is much more efficient as it catches smaller particles.....and the only reason that industry is changing over to paper is cost......takes 5 minutes to change a 10 paper filter vs an hour to servce the oil bath......goes with the same thinking that you don't rebuild car and truck parts now days you just R&R as it is less labor

unless you drive on dirt roads....often......changing to dry is only worth while if you don't like to get your hands dirty....

cleaning the oil bath is simple.

1. Drop the pan
2. pull the screen
3 clean the screen
4 reinstall the screen
5. drain oil from pan ( leaving the last little bit
6 clean pan
7 reinstall drained oil
8 top of oil
9 reinstall pan


I can do all three filters on my 04 in about an hour and a haalf.... and it costs me maybe 2 qt of oil

with the crap my filter pulls out of intake air driving on freeways........a paper filter system would be restricted in short order

[JohnEd]

OOOH YEAH, TAKE BIRD

I think I will change over from paper to the oil.  The post about the turbo sucking out the oil proves that these things are displacement critical.  More air flow to filter needs a larger oil bath filter.  I will be looking for tech info on sizing if DD comes up empty on fact advice.

Thank you all

John

[lostagain]

My 4-71N is now pulling about 500 CFM trough the oil bath. The 4-71T will pull about 800 CFM. Like I said earlier, I rented a fan last week rated at 2000 CFM and duct taped it to my filter so it was sucking the same way the engine does. The fan slowed down some (40w oil, too heavy for this time of year) so I don't know exactly how many CFM I was pulling, but I estimate 1000 at least. It did not suck oil out of the filter. And I don't think it would because the air flow does not go through the oil but over it and flings the dirt at it. The air does pick up some oil, but it is caught on the way up in the mesh element and drains back down to the pan. At least this is what I understand from the description in the DD manual, and from observing when I did the test with the fan. Are my asumptions right? Anybody out there thinks I'm wrong, please tell me, because I don't want to hook it up to my newly rebuilt turboed engine and suck oil into the intake. It would make a mess, and worst, it would make the engine run away running on oil. Not good.
Also, how much difference would a lighter oil make? Like even a 10w? The DD manual says same weight as in engine. Let me know.

JC

[NJT 5573]

JC, hope it works ok for you. I'd be very suprised if you unhooked it, even if it works out and tied some panty hose over the inlet for a trial run that you would not find a noticeable power increase. That was my experience. go big its better.

[kyle4501]

Did any turbo charged bus (or truck) come with oil bath air filters?

I don't remember where I read it, so it may not be reliable. . . but, I remember reading about how the turbo doesn't tolerate oil mist in the air & the mist could cause rapid wear of the impeller. That was why the paper elements were developed.

[lostagain]

I took the intake tube from filter to blower off, and it is dry. But this is before installing the turbo. So it is a good question. Does anybody out there have a turbo whith a oil bath air filter?

JC

[JohnEd]

Guys,

I remember that I was told that the ob filter is sized like a paper.  You increase the air flow significantly, you get a bigger filter.  I guess the difference is the result of not sizing things correctly.  Too small an oil bath gives you too much velocity and you suck the oil up into the screen at least.  Too large is where it got sticky....that resulted in to slow a air flow and the dust particles got a chance to flow around the corner and make it into the engine.  The other gem of wisdom was that they are hard to size for an engine that runs at a wide range of rpm.  Spec it for WOT and idle filtration was not as good.

A lot of "what I was told and remember" is the subject of my question.  I only have "bigger", "to slow", "To much velocity", etc. and thats not enuff to make a decision or even to ask for availability.  The rpm is 2300 and the displacement is 8V71, 8v71T, 6v92,.......  What is the airflow for these?  I can figure normal asperated but the DD is supercharged at least and mine will be turboed....soooooo?

From this thread I learned that the entire filter doesn't have to be removed for cleaning and that most of the oil is saved.  It is a slam dunk from the ecology point of view.  You report that it filters out smaller particles and if overdue for service it still doesn't get restrictive.  Forgiving?  Outstanding!  It is messy to service but not difficult or time consuming.  I really don't mind getting dirty if there is a good reason or even a not so good one.

The engineers comment was the real clincher to a mind that you had already made up.... paper wins because it is easier in terms of man hours.

Thank you all for your excellent comments.