adding a 98 RS plenum

[illnastyimpreza]

I've been debating what intake to go with on my 91 legacy L. But I think I might put the intake plenum from my 98 RS on and add a cone air filter w/ heat shield....or should I go with a K&N pannel...

any sugestions?

the 91's didnt have the intake plenum. I wonder how it will effect it...

[THAWA]

What part is the plenum?

[Nomake Wan]

Plenum = Snorkus

Somehow, I don't think that it sounds like a good idea, considering the sheer number of posts here telling people to remove the plenum/snorkus.

That K&N Panel Filter idea is probably the way to go in this instance.

[vrg3]

I think he's referring to the airbox just aft of the throttle body on newer NA Subarus. Technically it's not a plenum, since plenums are supposed to be downstream of the throttle plate, but it serves a similar purpose. I wonder if you need to tweak engine management to take full advantage of it.

[THAWA]

What's the purpose of it?

[vrg3]

From what I understand, an intake plenum is basically supposed to act as a buffer, storing reserve air for rapid increases in airflow at the valves.

Technically, the little portion under where the ignition coil pack mounts is the plenum. It's really tiny though.

[scottzg]

I hadn't posted yet because i was thinking of where vrg is referring.

If he's referring to the piece that goes from the maf to the throttle body, it's for throttle response. A step away in terms of outright performance. Not much hindrance or benefit either way.

[illnastyimpreza]

yea I was refering to the airbox. But I have been thinking about it, and am going to have to stick with the stock intake. The airbox gives me too much low end torque...and takes away from my high end @ the same time.

Now my delema is, K&N pannel filter.....or K&N cone with heatshield.
I just bought a WRX hoodscoop, So I might channel the air to a cone filter....might be tricky to build though

[scottzg]

The airbox is not a restriction. It's not harming your top end. What will harm your top end is sticking a cone in your engine compartment, where it will suck up hot air and the short runner length will provide for a poor signal from your maf, eventually possibly destroying it. If you want some noise and some psychic hp, take out your snorkus in the fender. Me, i would leave it alone.

[Rescue Wagon]

I would recommend you stay away from K&N Filters.

When I am not driving my Legacy I have a Dodge Cummins that I use. There are numerous tech articles out on the K&N filters allowing fine particles of sand and dirty pass and really messing up Turbos on the Cummins. So with that said I would assume it would cause the same damage on a subaru.

Just my $.02

James

[THAWA]

K&N's aren't made to filter more, they're made to flow better. How do you flow better, with less restricition. Bigger holes = less restriciton.

[vrg3]

James, can you refer us to any of those articles? I'd like to read them.

I've been told that many "K&N vs. paper" comparisons aren't fair tests because they test brand new filters against each other. Apparently K&N filters actually don't filter very well at first, but after they collect some dirt they start to filter better. So I'm curious to learn more about how the tests were done.

[THAWA]

wouldn't all filters filter better after they start filtering though?

[vrg3]

I suppose, but it's baked into the design of oiled cotton ones, supposedly. I don't know... that's why I want to read the papers.