anypne planning on running a K&N filter read this first

[jcb]

it doesn't really matter that it is on a deisel, due to the volume of air they shift the filter is more important than a standard petrol.
but given most of the cars on here are turbos and chipped/tuned/fettled and massaged the filter is more important on our cars.

check out how badly the K&N does in all tests apart from restriction.
The only reason I can see that K&N claims increased horsepower is by having the least possible restrictive media that lets anything apart from gravel through.
what makes it even scarier is that it seems to clog up very quickly as well.

Interesting reading:

http://duramax-diesel.com/spicer/index.htm

 

[Matt82]

been saying it for years

 

[aragorn]

Its not just K&N mate.

ALL performance filters are crap at actually filtering, which is why a) they require oiling as the oil acts to partially mask how bad the filtration is and b) no manufacturer fits them as standard.

I'm sure theres also some evidence to suggest that engines which have been running "perfomance" filters for long periods of time, show a lot more internal wear than engines having run on OEM paper filters.

The stock paper filter on your A4 is MORE than capable of flowing enough air. The RS4 element is no different in size to the A4 item, and the RS4 happily flows ~400hp

 

[B5NUT]

I have avoided all K&N type filters as the only thing I have heard on the forums is over time they cover the maf with oil.

 

[Matt82]

my s4 has a dyno plot for 320bhp on a paper filter

wonder what filter a veyron has? paper as a guess

 

[voteforpedro]

Ran a K&N panel filter on both my previous cars and have been disappointed both times when you're promised +5hp and expect to at least hear some kind of audible difference, but no, it's exactly the same sound/power and there's a £50 hole in your wallet.

 

[Nitro]

Been hearing this for some time now but, why do so many well renowned tuning companies use them? Also if they are crap at filtering how come, if you fit one it does not effect your standard manufactures warranty ?

 

[SteVR]

Just use paper filters as previously mentioned above and change more frequently.

 

[Matt82]

id bet it does, or have you had a mechanical engine failure on a new car with an aftermarket filter where the manufacturer replaced the engine under warrenty etc?

 

[Audijarvis]

I've ran performance filters on bikes and to be honest the only thing I've noticed is an improvement in induction noise

+5 bhp on a car?

You'd be better off making the Mrs walk

 

[Nitro]

I am not defending K&N filters here, but when I purchased my Milltek system they recommended I upgrade to a performance filter to help with the extra breathing of the new exhaust. So i did, When I fitted it I could not really tell any difference. I have been running it for about five months now and it still looks like new no clogging at all. On the box and on a sticker inside it states this will not effect any warranty. But after again hearing all this I might change to a paper filter.

 

[aragorn]

Nitro: its Sales and Marketing...

Ofcourse they're going to tell you that you NEED this special additional component!

And yes, you should refit the paper element.

 

[Matt82]

my golf came with a K&N. i had it out one day for osmething and realised you could see through it, 1mm holes here and there. the intake pipes were coated with dust!

a mate of mine with a corrado had the same.

we had both swapped to pipercross foam and no dust since but TBH i wouldnt bothere again in the future. ill just stick with paper

 

[Nitro]

If I switch back to a paper filter is there a make you guys recommend, should it be OEM only, or any paper filter from a motor factor

 

[Matt82]

just for for the oem brands

MANN, Kengst, im sure there are others i cant remember.

i wouldnt bother with bosch. i put one of those in the GF's fiesta and wasnt impressed with the dodgy feeling foam surround. it didnt fit well

 

[Nessy]

I saw a cheap K&N filter kit on Ebay some time ago for the B5 and for a short while seriously considered it until I read online the fitting instructions and saw of all the required hacking and cutting about of the airbox etc to make it fit.
Needless to say I didn't go any further, glad I didn't now!......

 

[aragorn]

mahle and fram are big names in filters too

ours just has some generic thing from the factors in it.

 

[jcb]

I have been running it for about five months now and it still looks like new no clogging at all.

ha ha, that's because unless it is the size of a marble it has gone straight through the holes in the K&N material and into your intake system, sand blasting its way past your compressor blades mixing with a nice solution of cleaning agent (petrol) and grinding a nice smooth surface in your pistons, rings, bores and valves,.........

 

[Matt82]

its good to look at things positively

 

[B5NUT]

OK, I know this in not full size motors, but when I raced 1/5 RC (2 stroke petrol) I used a K&N + oiled foam filter over the top worked a treat no ***** in the engine, and the performance was good, however the K&N filter was almost always clean, but the foam filter was covered. If you ran the K&N without the pre foam then the inside of the carb was always covered in dust & crud.

The air boxes on Audi's from what I understand are very good for Air flow, and I've never used anything but the standard paper filter, and even on the performance Audi's I still kept with paper, if they can handle 420bhp why use anything else:icon_thumright:

 

[Matt82]

i dont mind foam ones tbh at least you cant see day light through them but you have to clean them with petrol, spray on special oil that costs £10 a pop. you may as well just get a new paper one!!

 

[aragorn]

and the oil then contaminates the AFM.

Series 2 landrovers used oil bath airfilters.... We've come a long way from 1963 to be installing them in modern cars tbh.

 

[matt_simo1]

What if you want more induction noise?

 

[aragorn]

make the airbox intake larger, or fit an exhaust.

 

[warren_S5]

Question:

I'll openly admit I think a paper filter element is a decent bit of kit, and if changed regularly provides exactly what is needed for OEM performance and good filtration.

My challenge to this, I've spent some time wandering round ITG's factory in Coventry, and whilst there was stuff that was clearly off limits, why is it that motorport companies are making investments in aftermarket filters if they provide zero value.

I think a common misconception is that an aftermarket filter will give you more power; wrong. So I'm told the surface area of the filter media itself is critical to the outright power that can be produed on a turbo charged car (more critical for a turbo than NA I'd guess), and also the efficiency of the intake pipework helps (S3 is dreadful as there are 3 seperate 90 degree bends in the pipework from filter head to just beyond MAF!). On a rolling road test the ITG system enabled the car to produce a marked improvement in top end performance and bhp across the curve (from OEM).

I'd love to believe I could fit a paper filter and forget as Audi would love it, my wallet would love it, but is there a point at which you can tune where OEM becomes a limiting factor?

 

[badger5]

after market-Race, dont run to road car service intervals - Ever!

 

[B5NUT]

most motorsport companies will chuck there engine in the bin after a season, and even if they run the engine for another season then, the amount of miles that they do a year is nothing like that of a normal road car. There also running on clean tracks, or in a rally there is nothing in front of them chucking dust & grit toward the air intakes of the car. So called performance air filter are there so you can add a sticker to your shopping list which are plastered somewhere on the car! B7 rs4's run 420 BHP from factory and they use a standard paper filter, there is not many A3's or A4's that run more BHP than that. K&N's and the like are complete rubbish on road going cars.

 

[aragorn]

A paper filter IS restrictive. Not hugely, but people have seen perhaps 5-10hp gains on a tuned S3 engine switching from OEM paper to cone. People then go "WOW my cone gave me 7hp" but at the end of the day, on a 270hp engine thats not even 3%.

IMO the filter needs to be restrictive to do its job.

To trap all the dust and ****e, it needs very small holes, and very small holes are harder to draw air thru. By that very concept, to make a filter flow more freely, you need to make the holes larger, or increase the surface area of the holes.

An aftermarket filters often have hugely less surface area than the original paper filter, the paper filter is corrugated with many many folds producing a huge surface area, whereas most aftermarket ones have a single layer of foam, or some very slight corrugations. As a result, the holes end up being absolutely huge in comparison to the paper filter and hence let all sorts of crap thru.

Obviously sticking with the paper filter doesnt always work. The filter will eventually start becoming more and more restrictive as you tune the engine beyond the power levels the filter was originally designed for, however in the B5 models, the same filter is used on all models right up to the RS4, which implys to me that the filters restriction is sufficiently low to supply 380hp's worth of air. It should be noted that audi fitted an additional intake to the stock airbox on the RS4, which implys the standard intake snorkel wasnt big enough to supply the engines demand at this level, so its clear they HAD considered intake restriction, and modified the airbox accordingly, yet left that standard paper filter in place.

As a result, i'll be sticking with my standard airbox and standard paper filter!

 

[warren_S5]

my S3 is running somewhere in the mid 300's with S2+, so not enormous power really.

The OEM airbox is integrated into the engine cover, with an intake the connects to the front slam panel (highlighted in red below). In theory this direct airflow with minimal pipe bends / air disruption should be good, but the OEM scoop dumps a good proportion of its air into the engine bay as the intake scoop is sectioned into two halves, half of the air flowing to the engine bay, the other half into the filter.

The intake pipe behind the scoop is much narrower than the ITG (this is it's possible point of greatest restriction), but where everything becomes standardised is at the MAF where the pipework must always be 67mm in diameter unless MAF scaling is built into the remap software (believe APR may have done this on one of their maps).

Initially I fitted a Carbonia intake which passes all incoming air into the air box, but this is supplied with a dry panel foam filter which I really didn't rate that highly, so I switched it back to the paper one.

When I went S2+ it was recommended I went CAI as it was the only way to ensure power increases across the whole RPM range, so I got one as the map I chose had been optimised with this particular unit on board. Personal feeling is it seems to provide the most significant benefit at speeds that would be illegal on UK roads, and it was only when I went to Germany last year I felt a significant difference right at the top end speeds where the car just kept on pulling.

In a long winded way I'm agreeing that for 99.9% of day to day driving a paper filter is likely to be the best route for outright cleanliness, but in certain cars where the airbox ain't great there are some marginal performance gains to be had (which rarely equate well to bhp / £)!

EDIT:

Just found pics of another limiting part in S3 system (pipe from MAF)

 

[Jason.s]

My gf had a K&N Typhoon fitted to her old Mazda3 MPS 256bhp 280ft-lbs standard. Costs about £250 new. On the rollers it made 280bhp 320ft-lbs.

Agreed that a restrictive intake replaced with a better system will release a decent amount but an already nonrestrictive system (well not hugely as it`ll always have some sort of restriction) replaced by an aftermarket system wont provide much gain at all.

 

[hondansxr]

my honda s2000 had a cone filter inside the air box ?
when we took it out it says HONDA on the filter it is fitted in the air box so (imo) you can take the top of the air box off for mor ind noise ...