"Performance" filters.

[Sankekur]

So some of you will at some want to modify your car (being the enthusiast you are). One of the ideas that will be thrown your way is change the original filter with a so called "performance" filter. So in the typical South African modding culture you might assume that it is going to be better because it is now "modified", as we all know its not like BMW spend millions and years developing their cars (German engineering and how awesome it apparently is and all that apart). So it is pretty easy to improve on it by just spending a quick couple of hundred R.

If at this point if you are feeling like activating the fury of caps lock and start arguing, it might be better that you go do something else (maybe go up your post count by posting nothing but smileys in all the showroom threads or argue about street racing). If you can still keep moderately calm then continue reading

So a while back I had the misfortune of disassembling the intake silencer on a car that had been thusly modified, and an M car at that, and as we all know BMW really skimped on their engine designs, but they took this design skimping to its peak on M engines (especially the old NA ones). So it is the perfect place for this kind of modification.
Some info regarding this:
The car had done around 10k km with the filter, the filter was installed by one of the larger SA BMW tuning companies (along with some other "performance" upgrades, if you have played to many racing games you might call this a stage 1 or something like that) and the filter was one of the well known brands of "performance" filters.
This is what I found:

And this is the filter just as I look it out of the intake silencer:

Now everyone is free to look at the pics and make their own observation and draw their own conclusions. Always just remember if something is to good to be true then it probably is.

 

[S1NGH 001]

:nonono:

 

[Jerez]

I too am a bit sceptical about drop in air filters and the proposed increase in power. Well , perhaps with a combination of filters or more like a stage 2 cold air induction kit, complete with larger charge pipes, power pullies, a primary decat exhaust system with some software... THEN, perhaps you'd see a 20bhp increase.

A drop in filter alone won't make much of a difference apart from that sucking sound,, then again , just drill the airbox ( which I did on my jetta some 20 yrs back)

I'm missing the bypass track pipes and tune and still don't feel much.

It's not a total waste though cos you wouldn't need to change it as often as the OEM one.

 

[ChrisBrand]

At first i thought agggg not again. But i can tell u this with all honesty. I have used drop in filters and cai kits with cone filters and on none of them have there been dust inside at the top of the intake box or did they have gaps like that in the weaving! Honestly that looks like a drop in filter from china town.

But pics dont lie. And for obvious reason the brand shall not be named.

 

[Twinz]

The warning is well taken Sank.

That looks like a badly worn out filter. I am in favour of good quality aftermarket filters instead if the paper OEM filters. But i wont sell junk like that to a customer.

 

[dvst8]

The warning is well taken Sank.

That looks like a badly worn out filter. I am in favour of good quality aftermarket filters instead if the paper OEM filters. But i wont sell junk like that to a customer.

A good quality aftermarkert performance filter will never be in that condition after 10k kms.

 

[Speedy]

:thumbdo:

So often you get what you pay for,

Thanks for putting this up.

 

[Fordkoppie]

Sank - you do realize that that filter does exactly what it is supposed to do and it was very effective in its purpose.

We all know a performance filter is only there to keep out rocks and flies.
I dont see any flies on the inside, do you?? :fencelook:

So let me unleash the fury. THE FILTER DID WHAT IT WAS SUPPOSED TO:rollsmile:

---

A good quality aftermarkert performance filter will never be in that condition after 10k kms.

You are right, a GOOD performance filter will never look like that.

It will stay perfectly clean, since all the dust would have went right through:bravo:

 

[Sabretooth tiger]

true, thats why I dont believe in these

 

[moranor@axis]

completely agree... I would also bin the filter if the 'clean' side on my air box looked like that...

buuut I used a K&N filter (I understand yours was a K&N also?) in my car for well over 10k and the clean side of the air box was perfect with no dirt when i rubbed my finger on it...

not sure what happened here... maybe the filter did not seal well with the air box or was not oiled?

still a big concern because these filters are reusable so in adequate oiling and and not sealing is something to watch out for...

personalty i do not see anything wrong with wanting to use paper or cotton filters both have pros and cons...

 

[akash]

You get what you pay for. If its a cheapy and not fitting correctly dont expect top notch quality.

Thats why BMW charge R 1800 for their performance filters.

 

[Nikhil]

I replaced mine with a K&N and mine never looked like that however I make a point of oiling and cleaning it every 5000kms or when I do an engine wash. But I agree with moranor on this.

 

[dvst8]

completely agree... I would also bin the filter if the 'clean' side on my air box looked like that...

buuut I used a K&N filter (I understand yours was a K&N also?) in my car for well over 10k and the clean side of the air box was perfect with no dirt when i rubbed my finger on it...

not sure what happened here... maybe the filter did not seal well with the ait box or was not oiled?

still a big concern because these filters are reusable so in adequate oiling and and not sealing is something to watch out for...

personalty i do not see anything wrong with wanting to use paper or cotton filters both have pros and cons...

No way dude, Havent you heard ?

If you have a Performance Filter and drive past a school, you might suck up little kids.

:fencelook:

I also have been using K&N for years and never had the "Dust" issue.

:thumbs:

 

[Sankekur]

@fordkoppie: lol there where no flies inside :fencelook:


My problem here is, that this is supposed to be a good filter (at least this is if the manufacture can be believed) and the filter looks fine. It is just under closer inspection that the gaps in the filter media becomes apparent. The gaps are not just in certain areas, it is pretty much across the whole surface of the filter. The crux of this is that if light can pass directly through the filter then so can other things, and even though oiling the filter might fill up these gaps, this will be by surface tension alone so it will only be a matter of time until the oil can no longer fill the gap.

So it comes down to: Was the filter badly fitted? Though it is possible I would like to believe that even the most useless grease-monkey should be able to at least fit a filter without punching it full up holes.

Was this a 1 in 1000/ 1 in a 10000/ 1 in a 100000 or potentially bad batch issue? This is a problem for me if it is. I would not like to potentially put the health of my car's engine on the line for a company that has bad quality control.


Luckily I can say that BMW was smart enough to design this intake silencer (as they have done on many others) to filter using both the filter element and gravity separation. So luckily the rest of the intake path was clean.

 

[BillyBob]

It looks like a K&N - a BMC would've had a red rubber surround, and the substrate is naturally pink --- so we might as well call a spade a spade (or a shovel for that matter) and get it done with..

Filter hasn't been oiled - as simple as that.. People don't realize these things need to be oiled for a reason.

Edited to add:

dvst8 is right - that looks like a well-used filter - so maybe the tuning shop fitted a second-hand filter?

But that point aside - any unoiled cotton substrate filter will have light gaps when held up to the sun. The oiling process serves two essential purposes - to impregnate and swell the cotton to close the gaps, and to assist in trapping dust particles. It also binds the fibres of the cotton, so they don't disintegrate.

That MAY have been a new filter 10 000 km ago, that simply wasn't oiled when it was installed and thus the dry cotton's shrunk, as well as started wearing away.. The shop may have assumed that the filters come pre-oiled and just chucked it in.

 

[moranor@axis]

the K&N for i have for my e46 also has those 'pin holes' when you hold it up to the light but i do not have any filtration problem like you had...

K&N submit their filters to the same tests paper filter have to pass and they filter at the same level as paper...

how many paper filters do not seal properly and go unnoticed? not many are like you and me and will check that a filter is doing its job

 

[Peter@AEW]

I much prefer using a "standard" filter as opposed to the performance filters.

Manufacturers of performance cars will normally leave very little performance on the table to justify the expense of an aftermarket performance filter.

I use a K&N cone filter out of absolute necessity and not choice and I need to keep it well oiled constantly so as to preserve my engine and I doubt I am succesfull.

 

[Thunder]

I`m running a BMC performance filter and as far as I know i got mine with a life time guarantee, yes it gives a bit of a deeper sucking sound but not much of a power boost like some people would say.

But yes cleaning it regularly and oiling it properly does help a lot, and like Billy said maybe they just didnt oil it before installing it.

 

[Sankekur]

It looks like a K&N - a BMC would've had a red rubber surround, and the substrate is naturally pink --- so we might as well call a spade a spade (or a shovel for that matter) and get it done with..

Filter hasn't been oiled - as simple as that.. People don't realize these things need to be oiled for a reason.

Edited to add:

dvst8 is right - that looks like a well-used filter - so maybe the tuning shop fitted a second-hand filter?

But that point aside - any unoiled cotton substrate filter will have light gaps when held up to the sun. The oiling process serves two essential purposes - to impregnate and swell the cotton to close the gaps, and to assist in trapping dust particles. It also binds the fibres of the cotton, so they don't disintegrate.

That MAY have been a new filter 10 000 km ago, that simply wasn't oiled when it was installed and thus the dry cotton's shrunk, as well as started wearing away.. The shop may have assumed that the filters come pre-oiled and just chucked it in.

Nope, filter has had oil on it at some point.


How can something that is supposed to be a life-time part get worn?

How will airflow wear away dry cotton but not dry paper? If as everyone claims that the cotton one will give better flow, which means less resistance so there shouldn't there be less wear?

 

[BillyBob]

Nope, filter has had oil on it at some point.


How can something that is supposed to be a life-time part get worn?

How will airflow wear away dry cotton but not dry paper? If as everyone claims that the cotton one will give better flow, which means less resistance so there shouldn't there be less wear?

Okay then..

Cotton will wear and fray quicker as the fibres aren't as tightly bound. You send air past an even slightly frayed piece of cotton at 200+ km/h, and tell me that small individual fibres won't tear away from the edges? Why do you think the cotton gets enclosed in the mesh structure?

Strip away the the mesh and grip a small bit of the cotton substrate around one of the holes, then pull it - now do the same with the filtration surface inbetween the pleats of a paper filter - nowhere near the same consistency or fibre structure.

Air resistance isn't the issue - the structure and its bonding strength is.