STi air filter.

AlcyoneDaze · #1 05-09-2007, 01:01 PM

well, its that time again; my air filter is starting to get cruddy and I think I recall seeing somewhere here that you can replace the SVX filter with an STI drop in filter, which flows a little better and frees up some trapped horsies. So... I just walk in the Subie dealer and ask for an STi air filter element? is it worth the extra price? what model year should I be trying to get, etc?

Myxalplyx · #2 05-09-2007, 03:27 PM

Quote:

Originally Posted by AlcyoneDaze

well, its that time again; my air filter is starting to get cruddy and I think I recall seeing somewhere here that you can replace the SVX filter with an STI drop in filter, which flows a little better and frees up some trapped horsies. So... I just walk in the Subie dealer and ask for an STi air filter element? is it worth the extra price? what model year should I be trying to get, etc?

Chike....questions, comments, advice on this?

2NI · #3 05-09-2007, 06:06 PM

A lot of Subaru airboxes have the same design and that way share the same filter element. All Euro turbo Impreza's for exemple (GC8 & GDB) have the same airbox as our SVX's. So, that brings us here: if you cannot find a specific filter for the SVX, just ask for a WRX model.

I (like in a lot of my previous cars for ex. Impreza, M3, & current V40 turbo) put a "Green Filter" in the airbox. Why Green & not K&N for exemple? Well, it's cheaper & has a supposed better airflow.

Also because it's easy to find around here like it's manufactured locally (France).

Voilà!

Gizmotronicus · #4 05-10-2007, 12:27 PM

Quote:

Originally Posted by 2NI

A lot of Subaru airboxes have the same design and that way share the same filter element. All Euro turbo Impreza's for exemple (GC8 & GDB) have the same airbox as our SVX's. So, that brings us here: if you cannot find a specific filter for the SVX, just ask for a WRX model.

I (like in a lot of my previous cars for ex. Impreza, M3, & current V40 turbo) put a "Green Filter" in the airbox. Why Green & not K&N for exemple? Well, it's cheaper & has a supposed better airflow.

Also because it's easy to find around here like it's manufactured locally (France).

Voilà!

Plus oiled filters such as K&N will clog your maf over time.

Myxalplyx · #5 05-11-2007, 02:19 PM

Quote:

Originally Posted by Gizmotronicus

Plus oiled filters such as K&N will clog your maf over time.

What do you mean by 'clogging' your maf over time? How long does it take before it clogs your maf? All my Subarus (with the exception of the SVX) have K&N air filters. No 'clogging'! My outback has used a K&N air filter going on 9 years now.

SVXRide · #6 05-11-2007, 03:10 PM

I think the reference is to those that don't read the directions when cleaning/oiling their K&N filters...

The "GREEN" filter is also a good option.

-Bill

ensteele · #7 05-11-2007, 03:50 PM

If the filter is oiled to heavy, it may contaminate the MAF and get it dirty so it will not function properly.

Trevor · #8 05-11-2007, 04:10 PM

The name of the after market game and typically K&N. There are no wild horses out there awaiting a corral. The Subaru engineers have them all rounded up.

svxxx26 · #9 05-11-2007, 05:46 PM

I've wasted money on the K&N filters, et. al.

Placebo effect is a great description. I used mine until it got dirty, then replaced it with a paper Purolator filter. Same exact performance noted in the seat of my pants, so I think the "performance" filters are useless, at least in a stock engine.

Myxalplyx · #10 05-11-2007, 11:41 PM

Quote:

Originally Posted by Trevor

The name of the after market game and typically K&N. There are no wild horses out there awaiting a corral. The Subaru engineers have them all rounded up.

So, there is no horsepower to be gained by changing the air filter to an STi air filter you are saying?

b3lha · #11 05-12-2007, 02:31 AM

An ordinary paper filter, when new and clean, flows as much air as the engine needs. A "performance" filter that allows more air to flow provides no benefit because the engine will still take the same amount of air.

If you replace a dirty clogged up paper filter with a shiny new "performance" filter then of course you will see a benefit. But you would see the same benefit with a shiny new paper filter for a lot less money.

I ran one of my previous cars with no filter at all for a while. Better flow than any "performance" filter, but it made no difference at all to the performance.

My father inlaw lives in Africa where dust is a big problem. His fiat has an oiled filter and a ordinary paper filter in series. I guess the oiled filter helps to stop the paper one getting clogged up so quickly.

ItsPeteReally · #12 05-12-2007, 05:18 AM

Quote:

Originally Posted by b3lha

An ordinary paper filter, when new and clean, flows as much air as the engine needs.

Thats true at anything less than full throttle. Most of the time the driver limits the air flowing into the engine by applying less than full throttle and any other limitation of the airflow into the engine goes unnoticed.

But there is always a pressure drop across the air filter which increases as the engine revs rise and the engine tries to consume more air. If all other effects are discounted, removing the filter will increase the airflow into the cylinders when the throttle is wide open.

But there are other effects, which makes the outcome much more difficult to predict: the most obvious one being a change in the resonant behaviour of the inlet tract, caused by the change in the effective length and the amount of resonant damping.

My best guess is that the resonant frequency of the inlet tract drops and becomes 'peakier' ...... but the only way to be sure is to actually measure the flow

ensteele · #13 05-12-2007, 10:12 AM

For the kind of driving I do, paper filters will do just fine then.

Darren · #14 05-12-2007, 02:53 PM

Hiya,

I have an STI panel filter fitted, probably not worth the retail cost, the only benefit is the engine revs a little quicker in the midrange but nothing like the "add 20bhp" filter adverts claim for after market filters.

If you dont mind spending the cash there is a small performance benefit from the STI filter, bare in mind it was developed for the impreza in Group N rallying where they had to use a standard airbox, the flip side they may not be designed to last as long as a standard paper filter, time will tell, as at today mine has done around 4000 miles and is like new.

Darren

Landshark · #15 05-12-2007, 03:04 PM

for the price, the disposable STi filter is not worth it.

i have a Perrin foam panel filter, and like it alot (especially because it was free.) it is reusable, but unlike the crappy K&N, it filters better, and the thick oil it uses will not foul the MAF.