Late RS Impreza intake manifold on O4-07 STI

[Doppelganger]

Hello I'm inquiring about what modifications would be needed to install one of these big plenum long runner intakes from the 04 to 07 impreza on an sti.




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[Doppelganger]

Let's say if both cars are DBW would this manifold clear the avcs on the sti and will it also fit the throttle body?

I'm sure the fuel rail system would be a PITA to figure out as well.

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[Doppelganger]

Can an admin edit my title of the post since it was suppose to say late model RS impreza.

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[Grinder34]

I think i fixed it

 

[Doppelganger]

Ok im bumping this thread.

I wasn't going to do this since I was running stock turbo but I now have a FP Green turbo and am reconsidering picking a DBW rs impreza intake up. I already have injectors and would get the out front motorsports fuel rails with 18mm phenolic spacers to do the mod so that portion of the research is covered.

The main question now is do you guys think a 05 sti with pocket ported heads and supporting mods would bennefit from this manifold running a FP Green turbo?

I keep looking at these manifolds not necessarily because of the larger plenum but due to the fact that the runners are equal length and pretty much matched in flow.

Thanks for any response.

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[Doppelganger]

[MENTION=9]HolyCrapItsFast[/MENTION] do you have any feed back on this I'm really considering this manifold and since you will be the tuner I figured I should get your input before purchasing one.

I know you have to ramp up fuel in the mid and upper rpm area of the power band when using this manifold due to the increased plenum. In my opinion the real beauty of this manifold is the equal length runners which is why I really want it.

P.S. Sorry to bug you George.

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[Doppelganger]

Anybody have any ideals on this since there's one in a wrecking yard near me?

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[Doppelganger]

There's also a short runner legacy intake that looks to be nearly identical to the long runner impreza na manifold. This bolts up to the tumbler valve housings so spacers or new fuel rails would not be needed on the legacy manifold. If the legacy manifold flows similar to the impreza then this could be less if a headache to convert.

Also does anybody have feedback on my previous question about if the na manifold would kill my power band running a FP Green turbo since I've only seen gt35 and larger turbos using these?

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[Doppelganger]

This is the legacy manifold I was talking about I need to see if spacers are required to clear avcs. I think the spacers are not necessary since it uses the tgv housings from a WRX and if I recall correctly the the fuel rails are what hit the avcs.

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[Doppelganger]

Ok my head hurts from researching this na manifold subject. I've finally narrowed it down to purchasing either the 2.5i long runner large plenum manifold or purchasing the short runner large plenum intake manifold.

The benefits of the long runner is that it's a cleaner look but I will have to mod fuel rails and get 13-19mm phenolic spacers in order to clear the tgv housings.

The benefits of the short runner is that I can bolt it up to my existing ported tgv housings and use the same rails I already have.

I think either way I will need the 19 mm spacers since I will be using the FP Green turbo and figured the extra clearance won't hurt when installing the turbo inlet.

The screen shot is posted since it seems this individual gained power from installing the manifold on an older version of the FP Green. This helped convince me that the larger plenum intake manifold won't kill my power band even though I'm not expecting those a huge gain in power. Pretty much my FP Green HTZ will be a transitional turbo to a larger turbo so hopefully I should see gains from the intake while running the FP.



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[Doppelganger]

So I finally bit the bullet and purchased the long runner 2.5i manifold now I'll hunt down a deal on a set of phenolic spacers and fuel rail spacers to allow it to bolt up.

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[Doppelganger]

I figured I'd necro thread my old post and update what I've learned and post some pics of the different intake manifolds I've now collected some how . First I'll post some photos of the different versions I have.

From bottom to top sti, large plenum short runner NA, large plenum long runner NA and the large plenum long runner NA manifold I shaved.

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[Doppelganger]

Now the two main reasons I'm selling the shaved long runner and decided to go with the short runner NA manifold.

The short runner allows the use of the stock tgv deleted housings which has two main bennefits over the long runner manifold.

The first bennefit is that you dont have to use fuel rail adapters or custom fuel rails which allows you to use a variety of fuel rails. In my case I want to use the radium fuel rails with the dampers. If I used this combo the dampers would have made fitment a PITA with the long runner.

The second bennefit is the stock tgv housings keeps the fuel spraying on the back of the valves. Unfortubately the long runner uses large phenolic spacers to gain clearance so the rails can clear the avcs so the injectors no longer spray the back of the valves.

The only benefit I see in the long runner is it looks cleaner and it removes a set of gaskets since it dosent have TGV housings.

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[Doppelganger]

Some pics comparing the short runner large plenum na manifold to the stock sti turbo intake manifold.

The main take aways of the pic comparisons would be the NA manifold has larger plenum which is shaped nicely to distribute air to each cylinder compared to the flat back wall of the boosted sti or wrx intake manifold. The other main take away is you can see from the underside pics of the manifolds the na manifolds runners definitely look larger in diameter.

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