Air Filter Tests (Finally)

not on a compenstated turbo diesel no.

the filters flow a certain amount of air on some cheaper filters this is the flow rate with the filter 100% clean and with others its so many % clogged. so long as the filter is as clean or cleaner than the stated % of clogging and its flow rate is higher than what the engine can demand then your apples to keep using the filter as is.


a compensated turbo diesel has a device fitted to the pump that limits the amount of fuel that goes into the combustion chamber based on the pressure of the air going into the engine with the exception of the isuzu engine and modded engines all landy turbo diesels fall into this catagory. If the airs not there because the filters clogged the fuel pump only feeds the engine the fuel for the air available so the power drops off but the BSFC of the engine remains pretty much constant.

As an add-on to Dave's explanation (talking diesels), it is worth pointing out that the only time a reduction in pressure drop through the filter will make any difference is when the engine is operating at or close to maximum rpm - at all normal throttle openings, there is excess air going into the combustion chamber so a small drop (or increase) in pressure will have no effect on combustion. In fact, in most modern diesels the ECU will increase the boost to compensate for filter restriction, up to the limit of turbo capacity.

In a N/A petrol engine, filter restriction becomes more critical, since it acts as a throttle restrictor, and worse, in a carburetted engine, affects the mixture. (And standard filter restriction is taken into account in carburetter settings, so that reducing this will result in a leaner mixture at full throttle as well as a little more effective throttle opening.

But most of the "improvement" of oiled mesh type filters on performance is solely a perception of improvement due to increased engine noise from the loss of the silencing effect of the aircleaner. Aircleaners in most vehicles are designed as much to silence the intake as to clean the air!

John

For what it's worth, Donaldson air cleaner size selection is based on the filter passing the required volume of air when 80% clogged.

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Originally Posted by Brian Hjelm

My understanding is that Donaldson specify air cleaner capacity on the basis of achieving required flow at 80% of dust capacity. i.e still meet the required needs when 80% clogged. This is why a lot of people think the Donaldson spec. is over-large.

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Originally Posted by Brian Hjelm

For what it's worth, Donaldson air cleaner size selection is based on the filter passing the required volume of air when 80% clogged.

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And once more:D

Repetition is a proven method of teaching the slow learners. See how well you have retained this information. Next week we will commence learning the times tables.

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Originally Posted by Brian Hjelm

Repetition is a proven method of teaching the slow learners. See how well you have retained this information. Next week we will commence learning the times tables.

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1500-2000 repetitions and then it becomes habitual:D

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Originally Posted by rovercare

1500-2000 repetitions and then it becomes habitual:D

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as indicated by your tagline perchance?

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Originally Posted by Blknight.aus

as indicated by your tagline perchance?

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Nice observation;)

One thing to note is that cellulose is only a nominal filter, it will capture all particles only down to approx 33um. That is to say while a cellulose 10um(micron) filter will filter a 10um particle. The standard for construction and testing of that filter is that that particle has to be greater than 10um across more than one plane.

Referencing from my background (hydraulics, where we filter down to 1um) paper WILL NOT filter a particle that is 10mm long but less than 10um across other planes. Imagine a ribbon of Teflon tape, paper does not provide a diverse enough path through it's construction to capture it. Whereas a glass or polyester fiber filter media (known as absolute filtration) will capture all particles down to it's rated level.

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Originally Posted by clubagreenie

One thing to note is that cellulose is only a nominal filter, it will capture all particles only down to approx 33um. That is to say while a cellulose 10um(micron) filter will filter a 10um particle. The standard for construction and testing of that filter is that that particle has to be greater than 10um across more than one plane.

Referencing from my background (hydraulics, where we filter down to 1um) paper WILL NOT filter a particle that is 10mm long but less than 10um across other planes. Imagine a ribbon of Teflon tape, paper does not provide a diverse enough path through it's construction to capture it. Whereas a glass or polyester fiber filter media (known as absolute filtration) will capture all particles down to it's rated level.

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Sorry but you have NFI what you are talking about, and the above is 100% WRONG.

FIRSTLY - Filters are NOT sieves, they do not have a defined cut value/removal size (despite what manufacturers say).

SECONDLY - celulose material - like any other filter material - can be manufactured to be anywhere from 100% (HEPA/ULPA) filtration, down to any level you like.

THIRDLY - as you will note if you look at the graphs, collection efficiency goes UP for small particle sizes - due to diffusion - which is not an issue with hydraulic oil filters, but further reinforces the "you don't know what you are talking about" theme.

FOURTHLY - you seem to be talking about aspect ration AND/or fractal dimension of particles. Particles generally tend to aero/hydro-dynamically behave as per their smallest simension, however (a) your post is far too simplistic, and (b) unless we are talking about asbestos fibres, such particles are rare in air.