OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

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Southernboy
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OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Southernboy »

Last week I removed the DISA valve off the intake manifold to check it was still in good condition and no leaks or blockage to the little vent hole at back. It fits above the throttle and directly to the manifold. When removed, there is a round housing hole into the manifold which allows one to get a bit of a peek inside the area, I noticed that the surface of the interior looked sort of rough - almost like sand paper. I rubbed my fingers over the surface and was alarmed to find that the "gritty" surface came away on my fingers. This grittiness was made of fine material and I can only assume it is air borne dust which manages to penetrate the OEM air filter. Since I bought the car in Cape Town, I can only assume the fine dust might be beach sand which is whipped up into the air during the notorious southwesters which can reach hurricane force there at times. Nonetheless, it led me to consider that the OEM intake filter isn't as efficient as it might be, and I wondered if all modern filters are as "porous".
In the 50's cars were mostly fitted with an "oil bath" type filter. These were fugly things which sat on top of the carburetor and had a lower tray with an upper coarse wire wool type material filter. The lower tray had a centimeter or so of engine oil in it and the upper section when fitted, sat into the oil. Air intake passed through the mesh which was basically oil covered. Any foreign material was trapped onto the oil on the surface of the mesh with any larger material simply drowning in the oil at the bottom of the lower tray. I believe many large trucks (horses) and earth moving vehicles etc still use the oil bath filters on the intake because it is found to be more effective than a dry paper filter element common on cars.
This leads me to the next thought - There are K&N filters and perhaps others, which have filters which require oiling as part of their normal function and possibly these might be considered a higher performance filtration system than the dry paper element.
I believe some members have fitted these "oily" filters and would be interested to know their thoughts regarding the level of cleanliness on the intake manifold side of the filter.... ie. if anyone has been running a Z3 and could have a look see behind the DISA valve inside the manifold to check for any deposits it may shed more light on the degree to which "dirty" air is gaining access using an OEM paper filter vs the "oily" paper element type filter..
I am now considering removing the entire intake manifold and getting it steam cleaned inside all the air routes, and possibly converting to an oily K&N type filter and monitoring the interior of the manifold via the DISA valve locating port.
Any valid information from other members who are observant of this aspect would be welcome.
"Normal is overrated"
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Smartbear
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Smartbear »

Hi southernboy, I don't think its sand particles as that sounds the same as our z3 when I removed the disa for identical reasons (we live in essex not near the beach) i initially thought the disa itself had been wearing itself down in operation & coated the inlet with black plastic dust but the valve looked new.
I put it down to the ccv feeding oil fumes into the manifold where they become baked by engine heat?
That sounds unlikely as well I suppose! Maybe it's residue from a machining process to the plastic inlet? I don't think its dirt which has by-passed the air filter otherwise the maf snorkel would also be covered in this stuff & mine was not.
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Southernboy
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Southernboy »

Aha ! so you also had the "residue" in there.... I don't think it would be plastic from machining though, but possibly "baked" oil might be a possibility... at least I'm encouraged that it isn't gunk coming in through the filter and being taken into the cylinders etc..
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Smartbear
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Smartbear »

Yes, ours was coated internally as well, I also thought that as the disa look virtually new that I was discovering the remnants of the old disintegrated one! The particles seemed to "plastic" to cause any internal engine damage so I stopped worrying so much.
It would be interesting to find out where it came from though, our car runs a bit sooty so that made me consider the ccv, I recently poured some seafoam through the breather pipes so will see if that makes a difference......
Pat Slade
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Pat Slade »

Hi Southernboy and Forum visitors,

The valve issue is not a problem for most of our readers. The Z1 does not have a DISA valve like the Z3.
It is clear that filter systems have to cope with variable environments but it is likely that the OEM article has satisfied manufacturers comprehensive testing.
Before deciding to ditch the OEM filter for a K&N type it is worth reading the opinions on the many forums that have discussed this.
The general view seems to be that cotton oiled filters are unlikely to produce any performance gain and possibly cause problems from particles of the element being ingested.

Pat

PS See you have changed your ID icon Southernboy. Just drove Chapman's Peak Drive, great apart from cyclists and speed limits!
Del
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Del »

Personally I think the replacement “performance” panel filters are expensive rubbish. Against my advice, :D my son recently paid about £35 for a “Pipercross” one for the Z3. It was covered in the usual slimy, oily mess and wouldn’t even fit into the standard M44 air filter box which has not been amended at all. It was too large and try as we may, it was bowing and the box could not be closed back up. We sent it back to the supplier, complained and had a refund. We’ve never had a problem with any other conventional air filter which can be purchased for as little as £5. For the astronomical cost of £30+ these firms can’t even manufacture a product that fits – what impression does that give about their filtering ability?

BMW were clearly keen to achieve “lifetime” servicing items when they made these Z3s and my view is that had a truly “lifetime” performance panel filter been around, they would have used one rather than choosing the disposable paper ones which are a necessary service item.

Years ago, manufacturers used to publish an alternative "severe usage" servicing schedule so that things like air filters would be changed say, twice as frequently in dry dusty conditions.
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Southernboy
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Southernboy »

Hi Pat....... the cyclist on Chapman's are there to be terorised, and that's done by ignoring the speed limits.... :lol: :lol: :lol:
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Davejue1
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Davejue1 »

I have just purchased everything for a major service and I too looked at the k and n panel filters. After speaking to a close family friend who really knows his stuff he advised against a lifetime filter. He basically said there not worth the money and stick to a standard one instead, so I have! :)

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pingu
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by pingu »

It is well known that K+N air filters and hot wire MAFs do not mix. The oil coats the wire and the MAF sends a false reading to the ECU.

K+N are very good on old technology engines as they allow higher air flow for a given size of filter. They are also good on engines that do not use hot wire MAFs. Nobody (AFAIK), not even K+N are able to explain how their filtration works, but it does. It is thought that it works in a similar way to blowing through your splayed fingers as you quickly wave them infront of your mouth.

David Vizard starts discussing filtration at 4:30 and describes how he thinks the K+N works at around 10:20

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Alfie
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Alfie »

pingu wrote:It is well known that K+N air filters and hot wire MAFs do not mix. The oil coats the wire and the MAF sends a false reading to the ECU.
+1 from me.

I got a K&N out of the bargain bin at Halfords. Box was damaged so got it for about £8.
I started having problems after a few months which were traced back to a faulty MAF which had been coated with muck.
My well-respected BMW Specialist mechanic tried to clean it but didn't succeed and he had to replace the MAF.
Obviously I got rid of the K&N.
No problems since.

:!: So I suggest you don't bother fitting a K&N filter to your Zed!

Cheers.
A.
Last edited by Alfie on Sat 21 Feb, 2015 17:42, edited 1 time in total.
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Gazza
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Gazza »

Thread moved to Z3 section
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Gazza »

Interesting, I have a K&N panel filter fitted, been on for a good few years now but I have never oiled it.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

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Smartbear
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Smartbear »

Gazza wrote:Interesting, I have a K&N panel filter fitted, been on for a good few years now but I have never oiled it.
Hmm, I thought the k&n filter relied on oil in order to filter properly?
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Gazza »

I'll check it tomorrow
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pingu
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by pingu »

Smartbear wrote:
Gazza wrote:Interesting, I have a K&N panel filter fitted, been on for a good few years now but I have never oiled it.
Hmm, I thought the k&n filter relied on oil in order to filter properly?
Regards
If you watch the video, that's how he think it works (bearing in mind that K+N don't even know how it works :shock: ). The air pulses through the mesh and is attracted to the mesh and held there by the oil.
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Jonttt
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Jonttt »

http://www.knfilters.com/MAF/massair.htm

I've got one but air never passes through it :lol:

I am on my second MAF but that's another story :oops:
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Deano1712 »

The stuff in the intake may be baked on oil from the breather. If so its normal. I have a catch can in my motor to collect the oil. A drawback of injesting oil is that it lowers the fuel octane. Catch cans are fitted to mitigate this. It surprises me how much oil is stopped by the catch can.
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by peter2b »

I have a k&n filter on my robin hood been on my efi pinto engine for over 8years now I clean it every 6months and re oil it ,even though I only do about 2k miles a year never had any problems with the hot wire maf unit
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Del
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Del »

I'm surprised that either K&N or other "special" air filter manufacturers haven't done some sort of accurate experiment. It would be very easy to compare two filters put into two identical cars, covering identical mileage in the same area. These could be accurately weighed to establish the amount of particles filtered.
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Re: OEM AIR FILTER ELEMENTS vs "OILY" K&N TYPE FILTERS.

Post by Hoppo1979 »

I've fitted a Pipercross unit to my 3.0 Z3. Slotted into the standard housing no issues. My car does very few miles, 2,000 miles a year very max. Car feels great, very responsive. I will keep an eye on things though.
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