Green Filter versus Stock Filter
 

I know this probably has been discussed to death but its hard to be original anymore!
I bought a green panel filter the other week for my almost stock blobeye and just fitted it yesterday. I couldn't be sure, but the performance felt worse, so after an hour of B road hooning, I mean testing, with the green air filter, I replaced it with the stock filter and then performed the same amount of testing for a direct comparison. I have left the stock filter in place because it feels noticably better to me.

I know there are little rubber lugs that need clipping from the green filter so it fits properly in the filter box and I did that and it was sitting right.

Having read/asked around the general consensus is that replacing the stock filter with one of these performance filters shouldn't require a remap right? Has anyone else experienced degraded performance after fitting one of these performance style filters?

Cheers!

It's unlikely you'll see any noticeable gains from it so it's probably all in the mind. The bog standard OEM paper filter is actually pretty good at doing what it does :)

And half the price..
thanks Graz

ive got k&n and it is better at high rpms

worse at low rpms or no difference?

I've just purchased a K&N panel filter, which I intend to fit on my stock Hawk this weekend.

I'll let you know if I see any difference.

please, I'd be interested to hear!

No worries. I've always been an advocate of the K&N panel filters, I've had one in most of my motors and they've always improved performance.

Just a suggestion, (and I'm sure someone wiser then me could correct) but I'd give it a good 100 odd miles on a panel filter then swap back to stock and see if you can feel a difference then as I wonder if it's just a case that the ECU needs to relearn it's block, as the air flow may be slightly different, and therefore the fuelling is not quite right? :wonder:

I've fitte a green cotton to mine 6 months ago, I didn't nessesary notice any difference other than slight sound, when I changed back to my old filter for an experiment the car behaved odd everytime the clutch was pressed the revs dropped bellow 700 almost wanting to cut out

Ah so I had a similar thought, maybe the increased airflow made it run a bit lean or something..could that happen? With regards to the ECU, to what extent can it adjust itself?

Ok, so first and foremost, I've always worked with NA in the past, so I may be talking out of my bottom with forced induction. If so I'll be glad to be corrected, but my understanding is something along these lines (bearing in mind that in reality I believe it to be a LOT more complicated)

The ECU takes readings from several sensors across the engine, taking into account several parameters like air volume, temperature, coolant temp, crank & cam positions (as well as heaps of others) to calculate the "burst" of fuel for an injector (amongst other things like advance/retard timing due to fuel knock). It also "learns" how you drive the car (in terms of averages) to calculate the most relevant fuel "trim" (be that +/-). Don't get me wrong you will not notice a massive difference over normal running, BUT if you replace the air filter for one that is more free flowing, then the ECU needs to relearn the "averages" as the given values will "stretch" the upper/lower limits of the average, if you get what I mean.

On Vauxhalls it's called "ECU BLOCK LEARN MAP" (well, it is on My software anyway! Lol)

Interesting! And sounds valid to me, even if you are talking out your bottom :)

Well I hope I'm not.

As you were keen to hear my results, I swapped mine over this evening for you and the results are nothing less than amazing!

The throttle response is better lower down in the revs, and my tickover is much lower too. Settles around 6-650.

I have noticed after a good blast that its hunting slightly, but I reckon this is the ECU settling down to the new air flow reading?! Lol.

Either way, I'd say it SHOULD make a difference with a panel filter. It certainly has with a K&N anyway.

I'll let you know more as I put some miles on it!

wow ok that's good feedback! thanks for letting us know

No problems. Just done an oil change today as well... Would you believe it? Feels even better now. :D

Cheers

Well my Blob came with a foam piper cross filter which I didn't like the look of, so I stuck a low miles STI one I had sat in the garage, after a bit of hunting at idle and the odd low speed cut out coming to a particular round about it now drives much better than it did when I first got it, so in my experience SOME filters do make quite a difference, now wether the piper cross was better than a standard WRX filter I don't know but the STI one is better than the piper cross. IMO :thumb:

Interesting, I contacted a dealer to get my hands on an OEM filter and they offered me the Pro-R version which is a pipercross number, guess there are no definite answers on this topic huh!! How long did the hunting and cutting out last?
Frenchwood - has yours stopped hunting yet?

Yeah it's stopped hunting now matey. Didn't take long at all to settle down.

It's pulling like a train now, and I can tell the difference between stock, although I did go the K&N route, as I heard a few stories about Green filters before (Many many years ago) and have been K&N loyal ever since!

Methinks I'm gonna try K&N next paycheque!

Cost me £35 on fleabay pal!

As above not long maybe 3/4 drives and it wasn't bad but noticeable at the first set of lights I come to which is about half a mile from home, then it just stopped doing it and felt more responsive and seemed to generally pull harder, wether that's in the mind I don't know, but i'm happy.:D

This thread is perfect for my problem. i am lucky to have a standard 2005 wrx 300 ppp with less than 25,000 miles on the clock, the car is pretty tight if you know what i mean. Thought i would treat myself about 2 months ago to a k&n panel filter for a bit of fun or additional noise. Totally disappointed and now very confused, at the top end revs it seems to love it (still) but i dont like thrashing the crap out of my scooby, thats the beauty of a turbo, you can drive it fast sub 4,000 revs.

Anyway, i have poor throttle response, low idle, it isn't surgical on the go peddle as before, and pulling at low revs is reduced. I now have the issue of trying to sort this out. So my methods will be:
1) put the standard filter back in and test drive.
2) check the maf sensor isn't dirty due to excess oil from the k&n???
3) try the above with or without re-setting the ecu via battery disconnection.

Will let you now how i get on after the weekend testing.

Did you blot excess oil off of the filter before fitting it mate? If not, give it a quick blot, clean your MAF and try again.

Cheers

Not sure about modern fuel injected cars, but when I had my Citroen AX GT I fitted a K&N air filter. In the kit there was a jet that had to be swopped in the carborator. After doing this had to have it tuned as it altered the air flow. However, in winter I was driving with the choke out all the time. Therefore I went back to original air intake set up & another re-tune.

I also had a complete Scorpian stainless steel exhaust system fitted from the manifold.

With the K&N air filter & the exhaust I was mean to have increased the BHP by around 8-10 BHP.

Sold the car & included the K&N filter to a kid. He rang up to say what is wrong with the car as when fitted the K&N filter all the power had gone, so had to tell him to get it tuned.

As a thought - car manufactuers spend a fortune on developing engines the way they are, so why change their original spec?

Modern ECU's will adjust the fuelling for the increased air flow. The main risk is that excess filter oil will be sucked on the MAF, causing it to read the airflow incorrectly, and thus; the ECU will fuel incorrectly.

Increasing the airflow to an engine *should* let it breathe better, and theoretically give better throttle response, and help with MPG. If, however; your engine isn't running perfect in the first instance, it can cause running problems, as the ECU will adjust fuelling incorrectly.

Original engine specifications are made to suit a wider audience, and as such won't necessarily be to everyone's taste 100%. Think about suspension for instance, they have to make a compromise over handling and quality of ride. In most instances, they'll go for a cross between the two, whereas a lot of enthusiasts will want plane old handling, at the sacrifice of ride quality.

If that makes sense?

Found this thread interesting. Spoke to a local car tuner who services and modifies Scoobies and rally cars, he advised me to get a green filter and avoid the K&N because the oil on the filter eventually coats the MAF sensor and can cause problems.

Spoke with a reputable firm in the UK whem ordering the filter and they said it was rubbish and the K&N was the best.

Anyway, went with the Green panel filter and the car runs really well with no problems.

K&N in my opinion, is the better filter. They're quite right about the oil though, but provided you blot them before fitting, there shouldn't be any problems. Also, when cleaning and re-oiling, you need to be careful on how much you use, and again, blot the excess off.

Mine has been running K&N for a while now, and seems happy enough *touch wood*.

Ok, please can someone tell me how much for a new MAF? or where to find instructions for trying to clean my MAF??

Guessing your testing didn't go do well? Still got crap throttle response?

PM me your model/year/engine code, and I'll link you for a new MAF, otherwise, a search should turn up how to clean MAF. Either that or a quick google.

Cheers M

Ok, so a little change this weekend. Took out the maf, didnt have time to buy crc type spray so inspected and gave it a gentle clean with a cotton wool bud. Black dirt visiblemon one side, cleaned up ok. Dabbed the k&n which was bone dry. Decided to bin the K&n and go back to the standard filter. Engine was sharper and when you gas it, it had the old winding up noise, like a winding up on the turbo.... Perfect. Throttle response was also back.

Bottom line, i wouldnt go back to a "performance" filter which floods the system with too much air and makes it sluggish. I guess subaru and prodrive know what they are doing.

I then diaconnected battery for 30mins and then went for another burn. No real change, happy to be corrected but i dont think that does anything for resettign and ecu ona 2005 2.0 WRX? :luxhello: