New Air Filter...
- Thread starter t20lau
- Start date
Liverpool
K&N filters on modern cars are, by and large, snake oil.
A good paper filter is often cheaper over the long run, better filtration, and better air flow response. K&N's might have the cleanability factor, and good total peak airflow when actually clean, but that is about it. They take a good four years to pay for themselves, and in that time they do let stuff past/through.
I'd certainly want 100% OE spec filtration on a valvetronic engine anyway... and the oil can effect the air sensor readings or actually damage the sensors, making the engine run less than optimally.
Great in the desert when a paper one would fill up and not be re-useable, and your general arduous use means the engine will take plenty of stick anyway despite a bit poorer filtration... or on an old car with a pancake filter housing and a 1inch inlet, but in a normal very modern car in the UK on normal roads, they are pointless really.
Just marketed now on the idea they add real performance, but I've rarely seen it proven on an already good engine (which the 3.0Si is!)
A good paper filter is often cheaper over the long run, better filtration, and better air flow response. K&N's might have the cleanability factor, and good total peak airflow when actually clean, but that is about it. They take a good four years to pay for themselves, and in that time they do let stuff past/through.
I'd certainly want 100% OE spec filtration on a valvetronic engine anyway... and the oil can effect the air sensor readings or actually damage the sensors, making the engine run less than optimally.
Great in the desert when a paper one would fill up and not be re-useable, and your general arduous use means the engine will take plenty of stick anyway despite a bit poorer filtration... or on an old car with a pancake filter housing and a 1inch inlet, but in a normal very modern car in the UK on normal roads, they are pointless really.
Just marketed now on the idea they add real performance, but I've rarely seen it proven on an already good engine (which the 3.0Si is!)
I'm going by the experiences of a lot of more senior M owners than myself, and assume this relates to any BMW with a hot wire/film mass airflow sensor.
A dry, paper filter is all it needs. If it's had an oiled one on there for a long time then please check you MAF wire to see if there's any build up of oil on it.
The wire does have a self-clean function and this will heat the wire up to clean of most contaminants - however, over time the oil overcomes this self-clean and starts to become carbonised on the wire and reduces the capability of the sensor, which in turn leans/enriches your mixture with detrimental effect - not necessarily catastrophically for some time or not at all though.
Oiled filters are really for cars where the intake system is cleaned/checked/maintained on a short interval basis - i.e. racing. What works well on the circuit does not necessarily translate directly to the road, even though the marketing guys would like you to believe so.
A dry, paper filter is all it needs. If it's had an oiled one on there for a long time then please check you MAF wire to see if there's any build up of oil on it.
The wire does have a self-clean function and this will heat the wire up to clean of most contaminants - however, over time the oil overcomes this self-clean and starts to become carbonised on the wire and reduces the capability of the sensor, which in turn leans/enriches your mixture with detrimental effect - not necessarily catastrophically for some time or not at all though.
Oiled filters are really for cars where the intake system is cleaned/checked/maintained on a short interval basis - i.e. racing. What works well on the circuit does not necessarily translate directly to the road, even though the marketing guys would like you to believe so.
Hmm...Might have to rethink on the idea!
Anymore comment (good / bad) about buying a replacement filter?! I understand that paper filters are just as good when new, etc... as I was looking into this when I got the one for my VXR, but opted to get one as it would never need to be replaced and it seemed the majority of ppl modding their cars where opting to make the change!
Anymore comment (good / bad) about buying a replacement filter?! I understand that paper filters are just as good when new, etc... as I was looking into this when I got the one for my VXR, but opted to get one as it would never need to be replaced and it seemed the majority of ppl modding their cars where opting to make the change!
t20lau said:
Never is a long time!
It might save you a bit of time in that you don't have to replace it every 15,000 miles (5 mins, once a year maybe) - but you've still got to maintain it. Which means cleaning/soaking/reoiling on a similar interval, which will mean you actually spending more time maintaining it that you're trying to avoid. Unfortunately most people don't maintain them and just leave them in, and this is what exacerbates the MAF sensor fouling problems.
It's not just air filters.
Lots of people fit coilover suspension, or AP brakes. However these usually require regular maintenance and are not fit & forget like the OEM stuff. BMW have to ensure their suspension & brakes are strong enough to withstand daily road use, with the salt, rain, muck, and other contaminants spraying onto their components. The track-biased brake & suspension kits from the aftermarket (and I'm not talking the cheap end either) tend to not have the right seals or anti-corrosion properties of the OEM stuff as they're not meant to be used on daily drivers in all weather conditions.
On my Corrado VR6 I used to rebuild my AP brakes every year and even then there always seemed to be one (stainless steel) piston that was knackered/corroded. All my suspension was checked by AMD whenever I had new discs (about every 9 months
) to make sure they were in good order.A lot of people who buy aftermarket performance parts never bother checking them as they assume they're up to the longevity standards of OEM parts. I'm not saying the aftermarket parts are poor/inferior quality as I know they're not - it's just that they need a different maintenance regimen.
Anyway, rant over
mmm-five said:
Totally agree. I got a pipercross foam panel for mine, and it's a pain to clean, pain to dry, pain to keep the filter housing blocked while I clean and dry it, and then remembering it's sat on the radiator, not in my car if I have to dash out.
Then I have to oil it, and no matter how much I have used the MAF sensor reads slow for a week as the intial oil runs through and gets cleaned off (checked with diagnostic readout of maf sensor)...
It honestly is ALOT of hassle for what I would consider, about zero actual gain, while at the same time letting tiny particulates through the filter, as the post filter side of my airbox casing, suspended in oil, is fine particles... not so great what so ever, especially on my turbo engine.
Needless to say I've got paper back in there now.
Spend the £100 towards sports cats as they will give a real power gain!
Dave
Another urban myth?!!
http://www.knfilters.com/MAF/massair.htm
To be frank I've used K&N filters on my Z's with no probs for 10 years.
DAZ4 said:
Urban myth, or manufacturer PR?
So, the manufacturer dismissing a claim of problems caused by their product - where have I seen that before :roll:
I used to have them too, until I found oil residue along the walls of the MAF housing, intake boot and top of filter box - I used to just clean it with carb cleaner.
It wasn't until I bought an e34 M5 that I started hearing of problems with MAFs - and in 75% of cases they non-OEM filters in. Some were oiled (not just K&N) and some were just 'performance' filters with easier air-flow properties which let more debris through too. You'd also see impact marks on the MAF protection screen which meant something bigger than was meant too has come through the filter. It could be a problem specific to the generation of MAFs used in the 90's on e34s, but I'm not taking any chances for something that gives no independently proven gain.
They can give slightly better filtration (although 1-2bhp is insignificant and a dyno 'proving' this gain is pointless - a dyno operator can give you 50hp more/less by strapping the car to the rollers differently, or changing the data values on the computer to show whatever gain they think you'll want to see), and their claims of better performance are based on the fact that more air into the engine makes more power.
It's not K&N that I've I problem with, and I've used their products in the past - it's any of the oiled ones used for normal road use. I drive upto 30,000 miles a year and can't afford to have a car that's under/over fuelling, surging, losing power, etc. If I can reduce the number of variables in what cause these problems then it puts my mind to rest.
Why waste £40+cleaner+oil on a non-upgrade? You might as well put Slick50 or Ametech Restore into the engine, or put use one of those nano-particle waxes as they claim wonderful things too*
- Slick50 claims to reduce friction & wear and thus better mileage & less maintenance;
- Ametech Restore claims their CSL Copper/Silver/Lead forumlation fills in those cracks & pits in the engine reducing friction and increasing mileage - although independent analysis has shown there is no silver in the product at all and it's just paraffin with some heavy metals in suspension;
- Nano-particle waxes/polishes claim to protect your paintwork at a molecular level and also make the car more streamlined giving you better gas mileage
I've seen the effects on MAF sensors too. Namely my own, and relatively crappy filtration despite being well cleaned and oiled ever 10,000 miles.
The whole premise of the filters is stupid today. Yes, when intakes were not designed efficiently, mpg wasn't a massive concern as fuel was cheap, emissions were almost irrelevant, and we had pancake filters with 1" intake trumpets under a hot bonnet, YES, K&N's made a huge difference.
But today, on ram-air intake systems on highly developed engines like BMW's making in some cases over 100bhp/litre.
I doubt BMW make that much on air filter swaps as an OEM will make the filters for them to THEIR (BMW) spec for filtration and flow etc.
You only need test paper vs K&N or foam with a manometer to see there is hardly any difference worth bothering for. They cost lots to buy, are a hassle to keep clean and often take the life you might have the vehicle to pay benefits over paper filters that are just as effective and convenient to swap.
On my engine, a test was done with about 10 brands of filters, and OEM paper, and NO filter at all, and they all dyno'd within about 150bhp +/- 2bhp...
Not worth the money or hassle.
Dave
The whole premise of the filters is stupid today. Yes, when intakes were not designed efficiently, mpg wasn't a massive concern as fuel was cheap, emissions were almost irrelevant, and we had pancake filters with 1" intake trumpets under a hot bonnet, YES, K&N's made a huge difference.
But today, on ram-air intake systems on highly developed engines like BMW's making in some cases over 100bhp/litre.
I doubt BMW make that much on air filter swaps as an OEM will make the filters for them to THEIR (BMW) spec for filtration and flow etc.
You only need test paper vs K&N or foam with a manometer to see there is hardly any difference worth bothering for. They cost lots to buy, are a hassle to keep clean and often take the life you might have the vehicle to pay benefits over paper filters that are just as effective and convenient to swap.
On my engine, a test was done with about 10 brands of filters, and OEM paper, and NO filter at all, and they all dyno'd within about 150bhp +/- 2bhp...
Not worth the money or hassle.
Dave
TBH, I think depending on how you maintain the car, etc depending on the effects you see! I mean I've owned two other cars where I've have performance filters...never had a problem!
My mate has had 2 Z4's (3.0si and not the M), he's had performance filters in both! doesnt really make any difference to the car, but he's never had an issue either!
As for the cleaning...I spend about 3hours every sunday cleaning my car! Cleaning a panel filter once every few months wont break me!
My mate has had 2 Z4's (3.0si and not the M), he's had performance filters in both! doesnt really make any difference to the car, but he's never had an issue either!
As for the cleaning...I spend about 3hours every sunday cleaning my car! Cleaning a panel filter once every few months wont break me!
t20lau said:
But for less outlay over say 5 years, you get to not clean it, not have to buy it up front, better filtration, and a car operating at OEM spec
If there were huge gains, like there were on pre mid 90's cars, great, but the last decade has seen such drives for efficiency and optimisation that K&N really can't offer what they used to anymore, as the OEM are doing it from new now.
I'd look to the exhaust side for making real improvements to overall breathing, because the only way to really improve breathing at the intake end is with throttle bodies (ala M cars) and then a big fat intake plenum (ala M CSL)