Folks,
My XM 2.5 came equipped with one.
Do I beleive the hype that a properly cleaned and oiled one will catch more crud than a standard one? Or, a Citroen sage, and engineer of many years standing who suggests that the flitration element is compromised in pursuit of greater airflow, causing long term grit-blasting of bores, valves, etc?
Observations and comments welcomed.
rg
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20 years ago, a K&N filter would have given gains in performance over an often cheaply and badly designed standard filter.
Since then, official fuel economy figures have become important in Europe (I exclude the US in these comments as any country whose biggest selling vehicle is a Ford Pickup ..)
So to believe that a K&N filter makes significant gains in performance and economy (I will admit it increases induction roar) must require statistical proof over the lifespan of a standard filter (say 10,000 miles) .. that will take into account degradation of performance due to clogging with dirt.
Where are these tests?
Modern cars engine clearnaces are much closer : I drove a 1946 Rover 16 with a oiled wire filter: engines were clapped out after 30,000 miles.Minis of the 1960s lasted 50,000 miles before engine rebuilds.. on average.
I would never use a K&N filter..
madf
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A lot of differing of opinion on this subject- K&N filters are claimed to increase power output by a few bhp, but in reality, all they really do is increase induction 'roar'!
The filtering ability is not compromised IMO, but when they are washed and reoiled (recommended every 40k), care must be taken to do it correctly or it could be!
The greater airflow is simply from the fact its entire surface area is exposed, instead of being within a plastic box like conventional filters.
Is it a full induction kit fitted (i.e. cone shaped filter and cold air pipe) or just a K&N branded replacement filter that fits in the housing?
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If people really think that manufacturers go to great trouble in engine design, spending millions in development, and then spoiling their hard work by fitting an inappropriate air filter, then I suspect they are kidding themselves.
The change in pressure accross a decent OEM air filter is negligible. The gain acheived just by fitting aftermarket filters is also negligible.
If you choose to pep up your engine, then the fitment of a larger, OEM, filter and housing from another car is a much better way to make sure that the filter does not become restrictive.
It is remarkably easy to ruin the acoustics of the intake tract, the sizing of which usually exploits a number of Helmholtz resonators to control noise across the human hearing frequency range. Very little under the bonnet of a modern car is arbitrary. Most parts are sized the way they are for very good engineering reasons.
Number_Cruncher
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Well put, N_C. Not to mention the damage to sensitive and expensive items like the MAF from the oil on the filters.
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It's a direct slot-in to the existing housing.
rg
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The 2.5 XM tends towards the smoky, mainly because the engine does not spend much time above 3K rpm. This has been verified by other 2.5 owners.
Maybe this was the previous owner was trying to combat. He was no boy racer.
Thanks for the wise and learned replies. The turbo sounds like that fitted to a Paxman Valenta, as installed 125 (train) power units, healthy but loud!
It looks like an standard one will be slotted back in and the K and N saved for MOT emissions time.
Just for the record, the servicing kit consists of a bottle of detergent and some oil with a resemblence to Redex. I picked one up at a Walmart in Minneapolis for around USD8.00, so I didn't feel that "fleeced". 100k is recommended as a service interval, but I did mine at around 75K and it was flithy.
Thanks again.
rg
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The oil can seep out as droplets and fould airflow sensor.
Also, when you clean it, what's to stop trapped particles ending up stuck on the inlet side after which they become detatched and enter the airstream. I think they were more for old carburettored cars in the olden days, where the induction could affect venturi action..
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I seem to recall that you have to let the oil "dry out" a bit before you refit it.
rg
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Does not matter how much air passes over the MAF if the mapping is not altered it will not make the blind bit of difference
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Andy,
Slightly off-topic, but wewre you the chap HJ mentioned that ran a 2.1 XM to/from Dresden?
I just wondered if you "missed" it?
rg
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Some years back 'Car Mechanics' ran a Vauxhall Nova as a project car. One of the things they did was fit a K & N filter. They conducted before and after testing on a rolling road and IIRC there was no change in performance.
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Yes,But it is a 2.5 and it is daily use running on anything thats available,it is doing a almost weekly trip to Austria at the moment.
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We have had to bypass the fuel preheat system that goes through the cylinder head for some reason it stopped working but it is back to normal now,another 500000k left in it yet.More than can be said for my MB E200k.
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Fuel preheater bypass is a "standard mod.", as its notorious for letting air into the system. Leave it disconnected!
There's lots of help online if you need it.
The 2.5 estate is a seriously long-legged long haul freighter...
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