Swaggie
You may want to have a read here:
Air Filter Tests (Finally)
But feel free to ignore me. I have only been doing filter R&D for 10 years or so.
Pressure drop across a filter (inversely proportional to airflow) only increases slowly while a filter loads with dust. As noted, those on here who changed a (visually very dusty) filter didn't notice any improvement in fuel economy.
A new filter might remove 90% of the mass of dust reaching it when new, and 99% when dusty, as after a while the captured DUST captures the further influent particles, not the filter fibres. Air filters are NOT sieves. The pores in them are much larger than the particles being captured.
If you read the above tests, you will note that a dusty (donaldson) filter has less pressure drop (flows more air) than an OEM (coopers) filter. So the captured dust has LESS effect than the filter media/construction.
Moderator
In your tests the dirty filters had 20km of dusty roads... does this mean 20km or 20,000km?
Because that filter of mine had 24,000km of roads (maybe 5% would have been seriously dusty).
Also I have noticed an improvement in fuel economy... I spoke too soon before. The cars computer calculated L/100km is slow to react but when you calculate it out manually there has been an improvement.
06 SE V6 Discovery 3
Swaggie
It says 20k km = 20 000 km. Tdi filters have an integral cyclonic precleaner which removes at least 50% of dust before the filter.Originally Posted by djhampson
Your filter looked quite black. I suspect it had quite a lot of diesel soot in there. diesel soot is much smaller than road dust, so forms a much more compact filter cake (increasing pressure drop more rapidly)
Moderator
Ahh it does too.. I shouldn't try to read things 2 minutes after waking up.. brain wasn't active.
Thanks for the info isuzurover
06 SE V6 Discovery 3
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