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300Tdi - improved paper air filter for standard housing?

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Hi folks. 

I have a 300Tdi that has had some tweaks done:

Engine rebuild, with improved gas flow head; VNT turbo; full width intercooler; fuel pump tweaks. I also have the Donaldson/Wolf filter canister using the standard pipework. 

This work added a new noise to my car - the sound of air being sucked in through the driver's wing intake! Whether it takes in 'more' overall or not I don't know, maybe just more at the low revs when you're likely to hear it. I tend to drive the car much as I always did - ambling along, sitting at 58/60mph - but I just get there a little faster, and it's easier to drive in modern traffic. 

Now I'm toying with the idea of a Redbooster clutch (not getting any younger!) and there's no way it will fit with the Donaldson housing. 

I found this thread linked on here http://www.aulro.com/afvb/technical-chatter/50650-air-filter-tests-finally.html and that suggests Donaldson is a good idea over standard, but that there are versions of theirs that would fit within the standard 300Tdi canister. This might be the sort of compromise I'm after. 

Has anyone tried this? Putting a "better" paper cartridge filter into the standard housing? 

And I say 'better' but does anyone know, despite the sound of my new turbo sucking in air, whether the bog standard filter would be adequate or restricting for a mildly tweaked engine? 

There was talk of IRB doing a modified 300Tdi air intake - using the standard wing locations - but I haven't heard anything about that for a while. 

Thanks in advance

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I have a K&N filter on my 200Tdi 109.  It sits in the filter housing from a 12J as that is what I rebuilt the car with before fitting a Tdi.  The K&N was a plain corrugated cylinder, but the original paper filters for 12 and 19Js was corrugated paper with a plastic sleeve with stator vanes to grease a strong swirl inside the casing.  I suspect that was mainly to separate the oil from the breather before it contaminated the filter, flinging it to the sides of the canister.  In essence, it works like a Donaldson, though less powerfully than a full separate Donaldson unit.  I transferred that plastic sleeve to the K&N without difficulty.  Perhaps it would also fit a 300Tdi filter?

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I specifically wanted to avoid the K&N vs standard debate....🤐  I'd seen it cause a little tension here before, and I've personally been more persuaded by the arguments in favour of the standard paper/cellulose vs foam. 

The first pic on that aulro thread is this: 


2nd from the left is the Donaldson - part number P182052 I think. That looks very much like a paper cartridge which would fit in the standard 300 air box.

A bit of googling on that part number comes up with the likes of this. 


Which I suppose is as close as makes no difference to the standard one - yet the aulro tests showed it to be better than a new "LR" one even after about 20k km. Which brought me to the question about an alternative "better" paper cartridge for the standard housing. 

I should have put this extra info into my first post, but didn't have time last night. 

One thing I have learnt: I used to think it was daft that the LR filter had so much of the element covered up. Along the way I've read that it's to do with protecting the filter at the precise location where the air flow comes in. Apparently most of any dust/contaminants that come in via the intake would go straight to the filter at that location; it becomes clogged and can let stuff through. The alu. casing is to stop that and allow the dust to be dispersed. 

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I use a Donaldson type centrifugal filter at the pointo of entry (snorkel) , running to a standard LR paper filter (cooper or Mahl, I think). Having being brought up on K&N being the best thing possible, years of competition and hundreds of thousands of miles of off tarmac driving (in every dust imaginable) has opened my eyes. I do feel the 200Tdi filter is better (like most things 200Tdi - but that's just a personal feeling

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I spoke to a man from Mahle about this years ago. The plastic deflector if to deflect and centrifuge away water/damp and large debris from hitting the filter medium at point of entry. The 300 Tdi was not out at this time, but the metal shielding will be for the same purpose. If the filter media gets wet, it is likely to break up and let water and large particles and grit through.

If you look at both filters, I think the 200 Tdi item is better, as a lot more of the element is exposed to the incoming air. Remember also that there is a lot of difference in the quality and amount of filter medium, and as I keep on saying, a cheap air filter (also oil and fuel) is a false economy.

Having said this, I use K&N air filters on all my stuff, except for the machines with oil bath filters, and have done for more than 25 years and hundreds of thousands of miles with no sign of trouble whatsoever. Even after a dunking.

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My point was not about using a K&N (I removed one from my 300Tdi RRC and refit standard) but being able to transfer the finned plastic shield.  However, given that my 109 has a snorkel with cyclonic top and the plastic cyclonic filter shield, the filter is already protected from a lot of dust.  It was also deemed more important to have a filter that would tolerate oil contamination as the oil breather connects to the induction system immediately before the air filter on my vehicle, and that tends to lead to paper filters collapsing.  For most European or North American conditions, it is ample.  If driving Africa or the Australian bush, then I’d share your concerns and would fit high quality paper filters with spares carried on trips.

For what it’s worth, K&N and other performance filters are not usually foam.  They use oil soaked fine weave cotton, which is why they are oil contamination tolerant.  Foam filters would not be.  These fabric filters become more effective when moderately dirty and when damp (the purpose of the supplied oil they are soaked in), though that does cause more restriction to airflow in extreme cases like any filter.

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I might just order one of those Donaldson filters then and see what it looks like. I'll try and dig out a data sheet too to see if it's possible to compare its filtering performance with that of the standard ones.

On the question of the enclosed bit - metal in this case, but the finned plastic shield too - I dug out my old canister and removed the filter for a look. You can quite clearly see the "blast" effect, where moisture is being drawn through the intake and hitting the nearest point of the filter. 


That said, it does still strike me that too much of the paper here is covered. I think it was Sir Alec Issigonis (he of the Mini) who said: "If it looks right, it probably is right." I think the opposite holds too - but what do I know about filter design!


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