I'd never really heard of, or encountered oil bath air cleaners before I strayed from muscle cars to hot rods. And I don't really understand how they work, or why they were used. I did a search on here, but couldn't find an answer, so I was hoping someone might enlighten me... How, and why, does an Oil Bath Air Cleaner work? Thanks!
The theory is that the air is forced to make an abrupt turn (change of direction, usually 180 deg.) directly over the oil. Dirt particles, being heavier, tend to keep going in the same direction and take longer to turn...thereby ending up in the oil and being trapped. It works something like a centrifuge. Whether they are as efficient as a quality air filter is debatable- bore tests from the past would suggest not- but they do a decent job in my experience with older tractors. In those days the carburetor was generally an updraft type with the air cleaner assembly mounted fairly low and subject to all sorts of crud. It was easier and cheaper for the farmer to change the oil in the cleaner every day or so, than to go get a paper element from town. (Plus I doubt that they changed it every day, anyway, though most manuals recommended it in dusty conditions...)
Lol...What fine particles that get through the oiled mesh get stuck to the free oil in the tub. Oil bath air cleaners are actually one of the best at catching debris, not unlike your sinuses catching lake salt or dust
not really. the air doesn't flow thru the oil. The air makes a sharp turn and the particles are heavier than the air and hit the oil, then get stuck. if you put too much oil in it, you'll get a smoky mess. OOps, homespun you beat me to the punch!
They work by eventually coating your intake tract with oil and effectively lowering the octane rating of your intake charge. Instead of atomizing gas with air, you're atomizing gas with an air/oil mixture, since some oil vapor invariably ends up escapting the filter. Great in really dusty/sandy environments. Too many downsides otherwise.
HIJACK!! So on my 8BA air cleaner seen here.. DO I oil only the top felt part under the cap? Thanks..
Well thanks guys! I never had a chance to inspect one up close, and I couldn't figure out how the hell they worked, as I figured the air didn't flow through the oil. Now I know
And no they dont work like a bong or a hooka ,the air travels over the oil catching debris. a bong or hooka has a stem that goes into the water stopping the debris and allowing the smoke to rise out of the water. oil bath=travels on top of catching debris bong/ hooka =travels through stopping debris oil bath = oil bong/hooka=water just saying!!
32 Gnu's filter is not an oil bath...it is a mesh filter only, circa '36, and the big lower part is just a silencer. OEM oil baths have two mechanisms. There is NO mesh or filter at the intake part...air goes down the slot blow the lid toward the oil puddle, and momentum carries the bigger crud down into the oil where it perishes by drowning. Air then makes a U-turn upward and is drawn through a large mesh of woven stuff that is wet down and washed down by oil yanked up and then dripping down. On flatheads, the regular oil baths that sat on top of the carb could hold a pound of crud before oil was changed and the bigger side-mounted HD optional filter could hold THREE POUNDS of crap before choking. This huge capacity was very important in an age of dirt or gravel roads. Efficiency in filtering is much superior to the brillo-pad standard filter, less than a modern paper one. Eventually, the woven stuff may fill up with crud that failed to drip back down... Most cars had the silencer can/brillo pad one standard with the oil bath being optional or Deluxe.
They were the best technology available at the time, but when pleated paper elements became common the oil bath was a dinosaur. I'm still amazed at the old guys that say they were better than paper, actually they are a pretty terrible filter. I've taken apart Caterpillar engines that had the entire intake manifold coated with an oil-dirt mixture sometimes 1/2 inch thick, clear to the intake valves. If that mess made it all the way to the valves, you know it went in the cylinder too. The lifetime of Cat engines at least doubled, or more like quadrupled, when they went to dry filters, not to mention you pick up a bunch of horsepower.
Oil bath filters aren't that bad. In fact, paper elements on dirt roads need to be changed more often than the oil. They are a wee bit messy to clean. And yes, I am old enough to remember. The oil bath filter was a great improvement in its day; as it superceded a wire mesh filter that the owner was supposed to oil at regular intervals. The wire mesh filter superceded a horsehair filter that also was to be oiled regularly. Before the horsehair, a centrifigal filter was used. This filter looked like a tomato can with louvers cut in the end, and a hole in the bottom (air went through in a horizontal plane, as the carbs were updraft). The theory was that the louvers would cause the air to swirl, and the large particles would drop out the hole in the bottom. Very successful in filtering out grasshoppers and small birds; cannot say so much for dirt. One problem with the oil bath was owners / operators wouldn't clean and change the oil. When the oil filled to its capacity with dirt, both dirt and oil went into the engine. Failure to properly maintain the system is not the fault of the system. Jon.
The oil bath on my 8N tractor actually does work like a hookah but it is long and the air has to travel down a central tube and back up the outside thus turning the air 180 degrees it is long and vertical stopping the oil from getting in the intake tube. It has a bleed hole that allows the oil to flow back to level in the inner tube. They often have a "cyclone" attachment added to the intake to remove big chunks and use a mason style jar with a wire bail holding it so you can see when it is getting full and empty it. This style is a lot different than a car application though.
I find this kinda interesting. Last summer, when I was changing the oil on my '51, I decided to clean out the oil bath air cleaner instead of just adding some oil. When I took it apart and drained it, I found there was at least a quarter inch of compacted dirt/dust at the bottom of the unit. It was really compacted tight, and I had a hell of a time cleaning it out. Now, this is a car that gets used only on paved roads and on nice days. Looked to me that they work pretty good.
Oil baths work pretty good on heavy machinery, where the engine is running at governed RPM most of the time. On a car, where you might be chugging along slow in the dust, there isn't enough flow to keep the air velocity up where the thing works right. A paper filter works at all engine speeds.
The Jalopy Journal
