Oil bath air filter

[Pinkfoot]

Farm/horticultural machinery used to have oil bath air filters whereby the air is drawn down towards a bowl with oil in it.
The debris gets thrown into the oils and suspended therein.
It seems a very efficient method and is ancient.
Would this system not suit cars considering airflow could probably be generous?

[drybeer]

I'm not sure if would ultimately upset the MAFS with the risk of all that oil going through the system? I'm sure there is a good reason for sticking with regular or upgraded panel filters.

[cammmy]

I think you would have to do some research on that one as I didn't see anything other than other forum posts, with no testing to back them up. As stated though, I doubt they would play well with MAFs

[welwynnick]

Cars used to use oil bath air filters, but that was a very long time ago. Oil bath filters were only good at capturing relatively large, heavy particles, and fine dust like soot and cement breeze straight through. I'm currently involved in a research project into air intake particle separation for aircraft, and there's a lot science and engineering behind it. Truth is oil baths are little benefit, you just need some geometry to accelerate the air in a different direction and you can separate the air into clean and dirty streams, and exhaust the unwanted dirt.

The downside is that the geometry adds flow restriction to the intake, and the filtration efficiency isn't that high. That's why we use paper filters - better filtration AND low pressure loss. I don't think Fast Car readers realise how good paper filters are. Gauze filters let through twenty times the dirt, and intercoolers drop twenty times the pressure, so paper filters do their job rather well. And they're cheap and easy to service.

Nick

[cammmy]

Interesting, by gauze, do you mean K&N style filters?

By easy to service, do you mean on any car other than the RS6?

[welwynnick]

Yes, I mean cotton gauze filters like K&N, JR, BMC, Jetex, Green Cotton etc.

Well, air filters are USUALLY easy to service on any modern car.

Granted it's more difficult on the RS6, but then changing plugs or engine oil is more difficult on the RS6 as well.

Nick

[Pinkfoot]

We have oil bath air filters on the diesel rotorvators at work.
In the summer they live in a cloud of dust and don't seem to suffer any damage .
Are they really that bad Nick?

[welwynnick]

I doubt if there's been much scientific investigation into oil bath filters, but I've seen the results of computational fluid dynamic modelling of particle separation, and I don't believe that inertial filters are suitable for the sort of contaminants that road cars normally see. Nor are foam filters either.

For off road use however, with predominantly grass, insects, seeds, soil dust etc, oil bath and foam filters are probably good.

Nick