Thread: Air Filter Tests (Finally)

Originally Posted by cockie55

I have only limited knowledge of this subject so experts please excuse my fumbling thinking but doesn't this thought flow path apply:

1. Particulate matter in the combustion chamber is a recognised cause of extraordinary wear;

2. Fuel and air supply are the sole sources of that particulate matter;

3. Engine power and efficiency objectives are dependent on there being no air supply quantity and temperature "constraints" and this is before considering "opportunities" like cold-ram-air-fuel mixtures associated with modified air intakes;

4. The only air supply "constraint" is that associated with air supply, cleaning and monitoring devices; and

5. Assuming particulate matter in fuel will cause a problem with fuel supply system before it causes a wear problem in the combustion chamber, at what level does particulate matter in air supply cause a unacceptable wear problem having regard for avoiding the air constraint objectives identified in #3?

I am a fan of oiled air filters sitting in large appropriately designed air boxes (not found often in modern engine bay design) largely because while I have seen plenty of critisism of their being not as efficient in collecting particulate matter compared to other filter designs I have never seen any evidence that this lack of efficiency (what ever it maybe in particulate quantum and size) is engine threatening.

Having said that, this critisism of my K&N has had a impact as I keep a paper element handy if ever caught in a extreme dusty situations...LOL LOL

1. Engine wear can be caused by: Particulate matter anywhere in the engine, not just the combustion chamber. The sources of particulate matter are:
dust that comes in with the intake air
particles in the fuel
wear metals
soot generated during combustion

2. NO - see above - however intake air is often the most significant source (by mass) in an engine. However in many diesels equipped with good air filtration, soot levels are just as important, so many trucking companies do their oil changes based purely on soot content. The new LR engines have bypass filters to remove the soot from the oil, so it contributes less to engine wear.

3. Engines design incorporates restrictions in the air intake system. Standard turbocharger design uses a 1-2 psi restriction through the intake system. When cars are being designed these days, the restriction through the air intake and the (diesel) exhaust filter are given to the vehicle manufacturers by the filter companies, and used in the design.

Naturally though, easier you can get air in and out of an engine the more power it will make - which is what you are getting at I think?

4. Not sure what you mean.

5. I don't see how you can say that particulates in the fuel will cause a problem before dust in the air will cause engine wear. Rick130 (and others) have mentioned that the levels of silicon (dust in the air is mostly silica) in ENGINE OIL dramatically increases (as measured by oil analyses) when lower efficiency filters are used. Note that that is in the lubricating oil, not just the combustion chamber. Dust doesn't just go in and out of the engine with the exhaust gases, it stays in there, grinding away at bearings, rings etc.

As I mentioned above (and elsewhere), 2 F1 engines lunched their motors a few years back in one race in Bahrain, because the filters were so poor (and the conditions so extreme), that the engines sucked in enough sand to destroy themselves. This is an extreme case, but shows you whjat happens over a longer term with a normal engine.

Originally Posted by isuzurover

Hi John - next time I am back in Brisbane I will grab the oil-bath air cleaner off my Dad's IIA and do a test. I have never used an oil-bath filter on mine.

Filtration wasn't really understood properly until the late 60's and early 70s. Even back then, in terms of engine filtration, it was thought that you only had to remove particles larger than the smallest engine tolerance (something that an oil-bath filter would probably do fine).

Equipment to accurately measure filter poerformance didn't come along until the above dates either. Previously, light microscopy and (coarse) gravimetric measurements were all that was possible.

EDIT - you mention 200000+ km. However I don't really consider that a long time. My father's VN commodore had 350000 km on the clock when he traded it in, and he probably only changed the oil every 20k km, yet the engine had never needed attention and still worked fine. I have seen a few early 80's subaru engine pulled down after 400-500k km and they have still been within tolerances. And every time I jump in an (older) taxi I ask the driver how many k's it has done and what work has it needed. Many have had 600k+ Often with minor work like head gaskets and head rebuilds only.

Sure - engines last longer these days because of improvements in oils and metallurgy, but filtration is also an important factor which increases engine life.

Another source of dirt in engines is manufacturing residue, probably the worst being sand from the cast iron components. Improvements in manufacturing processes have probably made a big reduction in this problem in the last twenty years or so. Another source of contamination is the dirt that gets into engines when oil is topped up. Reductions in oil consumption forced on manufacturers by emissions legislation have probably had the unintended effect of greatly reducing this. When I was working in the desert forty years ago, engine wear became noticeably very rapid as soon as daily topups became necessary, as despite precautions, it proved impossible to avoid adding sand with the oil.

Another reason for the increased engine life is that almost all roads are now sealed, so there is a lot less dust around than thirty years ago. But the importance of filtration is clear from how rapidly and engine can be destroyed by even a small leak on the engine side of the filter.

John

Originally Posted by JDNSW

<snip>

But the importance of filtration is clear from how rapidly and engine can be destroyed by even a small leak on the engine side of the filter.

John

the blokes I listen to in lubrication all say that air filtration is paramount for engine life, more so than oil filtration, except, as Ben notes above, when soot levels exceed certain levels (usually in the 1.5%-3% range)

It's also worth noting that some oils come pre-dirty !
I've seen virgin oil tests showing unacceptable levels of iron and other contaminants.
One analyst told me that a client had extremely high silicon levels that were causing wear problems in his analysis that couldn't be accounted for. (he was using a very expensive synthetic oil)
They dumped it and added a good mainstream oil as a control and the silicon and wear problems disappeared. The new synthetic oil was contaminated.
This analyst had seen this occaisonally , which is a worry.

regarding oil bath filters, if you used an ester oil, would it be more effective seeing as esters are polar in nature ? (no one in their right mind would do this, seeing how esters are so damn expensive......)

At a minesite in the WA goldfields i worked at,we used to get such badly contaminated oil in the 1000ltr pods supplied by the oil company that the particle count was lower when the oil was sampled and drained from the machine.

We where dumping oil that was cleaner than the oil they where supplying.

Originally Posted by rick130

regarding oil bath filters, if you used an ester oil, would it be more effective seeing as esters are polar in nature ? (no one in their right mind would do this, seeing how esters are so damn expensive......)

Depends...

Oil bath filters mainly work like a cyclonic pre-cleaner - making the air turn around a few sharp bends, so it impacts either the walls/wire wool/oil in the air cleaner. There is likely also to be some interception (dust particles travelling too close to a wire (but with an inertia too low to impact), may touch the wire and stick.

The efficiency of both these mechanisms is inversely proportional to wire (fibre) diameter, and the wire is pretty coarse to start with. All the oil is really doing, is forming a coating on the wires to stop particle bounce, and washing the collected particles from the wires. The thicker the coating of oil on the wires, the worse the filtration efficiency will be.

Most oils wet steel well (regardless of polarity) - because that's what they are designed for. From what I have seen, viscosity is the most critical parameter.

What may improve the efficiency of an oil-bath filter, would be to spray the wire wool with a very light coating of something like spray grease or motorcycle chain lube (a very viscous oil) - and then fill the oil to a lower level than specified. This would mean that the captured dust stays where it is captures, and improves efficiency, rather than continually being washed off. Naturally this would mean more maintenance - in checking and cleaning the filter.

Since there was some confusion on the results in another thread - I thought I would summarise them here as well.

Originally Posted by isuzurover

I am definitely not trying to push any one brand, however, to summarise the tests results:

The bottom line is that ANY cellulose fibre (paper) filter element should be more efficient than a oiled foam/cotton type filter. However as far as the tests went:

The Donaldson filter with 20k km worth of dust STILL had a lower pressure drop than the Coopers, and had a slightly higher filtration efficiency. Either of these filters would work fine (as would other paper filters from reputable manufacturers), however if I owned a Tdi, I would probably go for the donaldson.

Note that the donaldson still has plenty of life left in the filter after 20k km worth of use - even though Rick130 (who supplied the filter) lives in the country and would (I assume) drive a lot of dirt roads.

I went to our local friendly Donaldson dealer. They don't have a listing for a 200 Tdi Disco filter. Can anyone help?