For those who may remember, quite a while back I decided to test some 300Tdi air filters.

Well I haven't finished analysing the efficiency data yet, but I thought I would post the DP results.

First the filters:

Left - Right:
Discovery 300Tdi K&N (thanks SSmith)
Defender 300Tdi DONALDSON - used for 20k km on dusty roads (thanks rick130)
Defender 300Tdi Coopers (OEM) NEW (thanks rick130)
Defender 300Tdi K&N - initially supplied with 20k km worth of dust (thanks rick130)


And also a 3.9V8 (RRC) K&N (thanks Hobie18) - you will notice that this is about the same diameter as a 300Tdi filter, but about half the length. Yet a 3.9L V8 would flow A LOT more air than a 2.5L Tdi - what were the engineers thinking...

So now for the pressure drop results - should be self explanatory???


So - the first conclusion we can draw is that V8 owners should switch to a TDI filter!!!

The 2nd conclusion is that K&N filters definitely have lower pressure drop - but at what cost (wait for the efficiency results) - when they are clogged, that would be a different story, but 20k km worth of dust isn't a lot in the scheme of things.

However the most surprising conclusion, was that a Donaldson (cellulose fibre (paper)) filter element with 20k km worth of dust in it, has a LOWER DP than an OEM (Coopers) filter does when NEW!!!

This can be explained by 2 things:
(1) Notice in the picture above, that the Donaldson uses expanded metal for the outer mesh, which has a high open area, whereas the OEM filter uses a drilled plate, which has a lower open area, and even dome closed areas. NOTE - all filters were tested without the plastic cyclone, which may make the DP curves of the 2 filters slightly closer.

(2) The Donaldson has deeper pleats, which means there is more filter material in the element, therefore lower average velocities and less restriction. It also should mean that the donaldson filter has more dust capacity (so your Donaldson element still has life in it rick )

Efficiency curves will be coming soon!