MarkF

I have changed to a K&N panel filter in my 93 WRX cos i'm not a lover of induction kits. What I want to know is has anyone tried to improve air flow into the box by drilling/cutting holes in the bottom of the airbox? My thinking with this is that it would let in more air (a la induction kit) but it still provides water proofing to the filter. Any advice would be appreciated.

Trout

iTrader: (1)

MRT recommend removing the resonator box which is set within the wing, feeding the standard airbox. In their view it releases nearly as much power as going to a full induction kit. You will need to remove the inner wing under the wheel arch to remove it - which is a relatively easy job to do.

If you do this it would be wise to relocate the air temp sensor to the entry point of the air box - I am not sure where this is on a 93 car - but it should be easy to find.

You can go to the next stage and fit a ram box in its place, feeding into the standard air box - PE do one and so do MRT - but they are expensive £2-400 plus fitting.

Cheers,

David

[This message has been edited by Rannoch (edited 31-12-1999).]

Mike Tuckwood

MarkF

I am fitting a Rampod induction kit in January, I will also be 'doing away' with the resonator, I will let you know how I get on and how easy(?) it is.


Mike

light12

hi all
hope you had a great xmas.
i have the rampod induction kit on my car
its very easy to install and sounds excellent
if a bit loud.
took the car to eilat ( the most southern part of israel ) about 400 k"m from tel-aviv.
and the ride was amazing.

Bob Rawle

IFAIK there is no air temp sensor on a MY93 car.

If you check out the cross sectional area of the air inlet system then that will tell you what is the restricting component. The resonator is there to damp out vibration from the air idle valve modulation and to ensure that the maf does not see violent transitions in air flow.


Bob

Bob

Trout

iTrader: (1)

Without wishing to disagree with Bob - removing the standard air box and fitting an induction kit will also remove the damping effect of the resonator - and many cars are fitted with an induction kit with no apparent harmful effects - perhaps Bob will correct me if I am wrong.

I removed my resonator today for two reasons - first of all it directly interferes with the HKS kit and secondly it will provide a small contribution of cold air from under the wing.

It takes about 45-60 mins and is a little fiddly but not difficult. To actually get it out you will need to remove the small crossmember between the inner wing and the spoiler valence. Don't forget to replace it once the box is out.

Apparently this is a fairly standard mod in Oz - if you don't go for the induction kit.

Cheers,

David

Bob Rawle

I agree totally about the induction kit David, thats why, having tried both methods, I run a Blitz cone ... much better breathing for my car. the only point is that if the air box has an entry or exit of smaller cross sectional area than the resonator then the restriction is still there. The air path is only as good as its smallest cross section, least thats my "rule of thumb". However if it works and all that.
Having checked out the underbonnet and intercooler air temp with the airbox and the induction kit I found no difference under normal driving conditions.As I said the Blitz is noticeably better dur to inproved air flow.
Maybe different on later cars but there is no "forced" draught from the inner wing on my car at all.There needs to be an air path through into the wing from the front of the car for that. Be wary of creating one, a couple of people have had trouble with hydrauliced engines due to water injestion after/during driving in flooding.

Bob

Trout

iTrader: (1)

At the risk of this sounding like a mutual admiration club - I agree with Uncle Bob that the maximum restriction will be the point with the smallest cross-sectional area or interruption of the gas flow.

I remember fond hours gasflowing everything when I built a Cooper engine for my first ever car - a humble Mini!

Having said that, Training WRX recommend the 'resonator-ectomy' as on the rolling road they have demonstrated a 3.5kw improvement at the flywheel with this change alone. Adding a free-flow panel filter will improve on this figure. This is as good as most induction kits!

I think the reason is that the 'resonator' does exactly what it says on the tin and creates a standing wave in the air at different intake velocities and ultimately slows airflow down

I also agree that fitting an underwing 'ramjet' collector does have significant challenges with regard to water ingestion - I am aware of one car that destroyed his AFM this way - although luckily not the engine.

Something worth trying if you want to keep the standard air-box.

Cheers,

David

MorayMackenzie

MarkF,

If you don't like induction kits, why look at drilling holes in your airbox? Doing this will greatly increase the induction noise your car generates whilst rendering large sections of the induction system (before the airbox) useless.

As to water induction, I don't think this is a problem with properly installed cone-filters unless you remove the bonnet vent blanking plates and don't make any kind of rain shield for the cone.

I have used standard, K+N element, hks cone and blitz cones in imprezas, I am very happy with the Blitz cone currently fitted.

Moray

BTW: Racelogic, UK Blitz distributor, gave me a 10% discount on RRP because i'm a SIDC member!

MarkF

Moray, its a sort of cosmetic thing. I just don't like the looks of cone filters. Admittedly some look better than others but I ain't a fan of them. I also think that by drilling the air box you will still get more protection from any water, not just from through the bonnet vent but anywhere else.

MorayMackenzie

If you don't like the cone-filter look, and moneys-not-a-real-object then how about something like the BPM carbon airbox/heatshield thingy that would keep a cone filter out fo sight and away from water and hot air? V. Expensive though, I would imagine!

MarkF

Hey Moray, like I tell my mates, just cos I drive an Impreza doesn't mean i'm loaded!!!

dmel

Following Rannoch's advice, I have also removed the resonator box. I can confirm that it is fiddly but not difficult. Take care not to destroy those plastic clips...

Is it dangerous to get water coming into the filter? The resonator box has a small hole at the bottom. I have not added a pipe in the place of the resonator box and therefore air is sucked from the wing and not behind the headlamp.

I cannot say that induction noise has increased as much as I wanted to. Will a cone filter increase it further?

Trout

iTrader: (1)

dmel,

water ingestion is not really an issue if you remove the resonator - it is only an issue if you then fit one of these expensive underwing scoop/ramjet things straight into the standard airbox.

Also, removing the resonator box is a route to gaining better high flow rates WITHOUT increasing induction roar. If you want induction roar - go for an induction kit - which will sound like a Dyson on speed

David