Thread: Air Filter Tests (Finally)

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.

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.

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.

And once more

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.

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.

1500-2000 repetitions and then it becomes habitual

Originally Posted by rovercare

1500-2000 repetitions and then it becomes habitual

as indicated by your tagline perchance?

Originally Posted by Blknight.aus

as indicated by your tagline perchance?

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.