Thanks Thanks:  5
Likes Likes:  10
Results 1 to 10 of 10

Thread: WRX Manifold on a STi

  1. Top Of Page | #1
    Daily Driver Robert Viehweger's Avatar

    User Info Menu

    WRX Manifold on a STi

    I've had a couple folks tell me that high horsepower STi's are using the 07 WRX manifolds because they flow better and are able to squeeze more hp out. Has anyone heard of this, because what little I've been able to find on the subject is that for most builds, it offers not a whole lot in gain for the swap. I figured someone on here might have heard a bit more on the issue. Thanks!
    @IGOTASTi.COM @HolyCrapItsFast


  2. Top Of Page | #2
    Basic Member

    User Info Menu

    Assuming you mean intake manifold, they are exactly the same manifold except one has crinkle red paint on it from the factory. High HP builds are using intake manifolds from NA Imprezas because they do in fact flow MUCH better (better than Cosworth on a flow bench) and are cheap. Well they were before people realized this. Also, some models don't use TGV risers so it doubles as a TGV delete as well. For a prime example of this go check out Jaeger Racing's track car.


  3. Thanks Robert Viehweger, HerThing thanked for this post
    Likes Robert Viehweger liked this post
  4. Top Of Page | #3
    Daily Driver Robert Viehweger's Avatar

    User Info Menu

    Thank you for the info. At what hp range does the NA intake manifold actually become relevant? High horsepower is a relative term to most folks. lol


  5. Top Of Page | #4
    Basic Member

    User Info Menu

    I don't usually see people do it until upper 500whp+. I mean technically it's better flow and that will help at any level but it's not a direct bolt in affair. As I recall it actually has a spot for an EGR that most cut off and weld shut. Outfront Motorsports has an entire manifold service where they trim off all the extra nubs and fill in all extra holes, plus for an additional fee they will give it a show quality mirror polish. They also sell fuel rails that fit it because the stock fitment STI rails won't bolt on as it's a different mounting point.


  6. Thanks Robert Viehweger thanked for this post
  7. Top Of Page | #5
    Daily Driver Robert Viehweger's Avatar

    User Info Menu

    Gotcha.. I'm shooting for mid 500's with this new build, and I have someone really trying to push me into it, saying 20+ hp gains, and I've got people who have dealt with these cars for a good, long while saying 5 whp at most where I'm at. Not trying to spend money on something with minimal gains. I'm not a dyno number whore. lol I won't feel 5 whp.


  8. Top Of Page | #6
    Drinks beer! HolyCrapItsFast's Avatar

    User Info Menu

    This goes in line with the philosophy "Don't do it just because its bigger". You need to component match everything and the intake manifold is a key component in the final number. Don't think of it as "what kind of power gain can this one component give me" (which is a relevant concept), but think of it as "what can this, in combination with all my other mods, give me". For instance the greater flow capacity that this manifold provides is only relevant for NA applications and Big Turbo applications mostly because of it's increased volume. For stock and mid size turbos, that extra volume can hinder performance in the form of turbo lag by reducing the flow velocity of the charge. You will have better over all performance from the STi manifold or the JDM STi manifold for stock and mid sized turbos. Remember that the charge is under significant pressure and the same restrictions that hinder NA application becomes a non-issue. But for the 500+ HP level you are striving for, my guess would be that you will be using a large enough turbo to create the flow needed to take advantage of the volume this manifold provides.

    This manifold also provide different characteristics for NA application versus Turbo applications. For NA applications the manifold is less restrictive and will provide more flow due to a less resistant path. The flow velocity becomes irrelevant because the charge is being sucked in. Technically the plenum volume can be infinite in a NA application. In a turbo application, flow velocity through the manifold is decreased versus that of an STi manifold and a pressure drop is realized because of the significant increase in plenum volume. You need to maintain a plenum size small enough to maintain pressure but large enough not to restrict the flow. Again this lends itself ideal for Large enough turbo applications. For anyone considering this for stock applications should probably re-think this as a performance mod.

    My journal

    Tuning & Service: Self Tuned
    Machining services: Bob @ Ace Crankshaft, Bayshore NY, Ralph @ Chudnow Manufacturing

  9. Thanks Batmobile_Engage, IGOTASTi thanked for this post
    Likes SudoSTI, Batmobile_Engage, IGOTASTi liked this post
  10. Top Of Page | #7
    Doppelganger's Avatar

    User Info Menu

    So a quick question that is not the easiest to find an answer on Google. So is it 2003 and below that are Drive By Cable with 2004 and above being Drive By Wire throttle on all the subaru models?

    Sent from my SAMSUNG-SM-G920A using Tapatalk


  11. Top Of Page | #8
    Basic Member

    User Info Menu

    02-05 USDM WRX is DBC. 06+ USDM WRX and 04+ USDM STI are DBW. All JDM STIs up to 08 are DBC. All 08+ JDM STIs are DBW. Like my JDM TGV-less intake manifold fits my 02 USDM WRX because I'm DBC, but it's actually from an 04-05 JDM STI that was DBC. Also part of the problem with compatibility for plug and play Haltech ECUs. They're AUS based so they had the DBC STIs there as well so they don't work in USDM STIs.


  12. Likes Doppelganger, HolyCrapItsFast liked this post
  13. Top Of Page | #9
    Doppelganger's Avatar

    User Info Menu

    I might buy a long runner 06 RS intake manifold for when it comes time for a larger turbo. I figure they will jump in value when they become more scarce.

    Sent from my SAMSUNG-SM-G920A using Tapatalk


  14. Top Of Page | #10
    Basic Member

    User Info Menu

    I don't recall if you were talking about going reverse intake manifold or not but if you are, one other thing to consider is that in order to flip the RS manifold, it takes modification to the plenum and much banging of your hood in order to fit. Since I'm already flipped, when the time comes to get a bigger manifold I'll have to pony up the $1k to get a Cosworth since I don't want to invest the time or money hacking up an RS manifold to fit.


  15. Likes HolyCrapItsFast, Doppelganger liked this post

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •