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2006 Forester XT Limited 4EAT
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2,008 Posts
Discussion Starter #1 (Edited)
Consensus is that just about anything will work, and only OEM - OEM benefit is bling.

This is an effort to clarify compatibility issues between Forester and other Subaru model fitment. It is a foregone conclusion that the biggest reported difference between intake manifolds is color.
If you have an other than stock intake manifold, please post your info in the following manner.
 

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Official sf.org decal guy
2006 FXT
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12,516 Posts
Forester Year: 2006
Forester Model: XT Limited

Comments: Intake manifold is from an unknown year, JDM 2.0L STi

This intake is NOT a plug n play. The intake will mount to the TGVs just fine but the JDM STi of the year my intake came from are drive by cable and not drive by wire. The throttle body side of the intake manifold is at a different angle than those of a DBW STi. They can be made to work, as it is in mine, but an adapter plate needs to be made.
 

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Premium Member
2009 Outback XT-B 5MT
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10,409 Posts
The bolt pattern at the heads are all the same. Every manifold will bolt up, it's just a matter of getting various sensors and intakes to work that makes it challenging.

For example, you COULD get a manifold from a 1991 Subaru Legacy, and it would work. Converting the various sensors (or disabling some, like the TGV's in some cases), is all it takes to get it to bolt on.

You COULD get a plastic manifold from one of the newer LGT's, and it would work. You would just need to sort out the throttle body routing.
 

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2007 FSTI and X 6 MT
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22,330 Posts
The bolt pattern at the heads are all the same. Every manifold will bolt up, it's just a matter of getting various sensors and intakes to work that makes it challenging.

For example, you COULD get a manifold from a 1991 Subaru Legacy, and it would work. Converting the various sensors (or disabling some, like the TGV's in some cases), is all it takes to get it to bolt on.

You COULD get a plastic manifold from one of the newer LGT's, and it would work. You would just need to sort out the throttle body routing.
Like rotating it for a fmic set up.
 

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'98 Forester
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503 Posts
The bolt pattern at the heads are all the same. Every manifold will bolt up, it's just a matter of getting various sensors and intakes to work that makes it challenging.

For example, you COULD get a manifold from a 1991 Subaru Legacy, and it would work. Converting the various sensors (or disabling some, like the TGV's in some cases), is all it takes to get it to bolt on.

You COULD get a plastic manifold from one of the newer LGT's, and it would work. You would just need to sort out the throttle body routing.
hUH ... NO ... the SOHC and DOHC have different bolt patterns / port configurations.... as well as the early "1991 Subaru Legacy" ... all 3 head designs have different patterns ...

Not sure if the early NA DOHC is the same as the later Turbo DOHC ...

One of the things I am working on is getting the '98 DOHC manifold to work on an '06 SOHC I-Active motor ... and it is not a bolt on affair ...!!
 

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05 2.5 XS
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18 Posts
So would swapping manifolds with my 05 n/a forester to another manifold produce better flow, or is it just for convenience of parts replacement?
 

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2006 Forester XT Limited 4EAT
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2,008 Posts
Discussion Starter #12
I really cannot say one way or another for N/A. I have seen no claims of increase power or flow by swapping any OEM intake manifold for another.
There are aftermarket manifolds with claims of increased flow performance.
There are also P&P services for OEM manifolds.
 

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'98 Forester
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503 Posts
So would swapping manifolds with my 05 n/a forester to another manifold produce better flow, or is it just for convenience of parts replacement?
I doubt you would see any gains swapping different manifolds on a stockish NA engine , even going with an aftermarket intake will not gain much if any .... If your Turbo or have a crazzzy NA build , then you may see a little ...
 

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2005 FSTi SG9 FSTi 6 Speed
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352 Posts
so from reading this, if I got my hands on a intake manifold from 2.0 rex, get it pnp, i should have lil to no fit issues on my 2.5XT????
 

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04 STi and Fxt
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169 Posts
So would swapping manifolds with my 05 n/a forester to another manifold produce better flow, or is it just for convenience of parts replacement?

The n/a manifold flows way more than the turbo manifold. The n/a manifold is IMO, the best manifold ever produced for flow rate a linearity. It is much better than the new cosworth, magnus, and others...

Now, the catch...

These manifolds, if placed onto a turbo car, will actually hurt performance a little bit. They simply have too large of a plenum for such small turbos. They really dont start to shine, or become worth the hassle until you are running a 35r turbo or equivalent. When you start to dip into the 500WHP zone, this n/a manifold will be good for a 75-100whp gain up top.

Another god thing about the n/a manifold is the fact that it is a long runner design(No tgvs) and it utilizes top feed injectors(better).

If anyone decides to get one of these, please note that you cannot reverse it(to make fmic piping shorter) unless you want to gut the bracing on the hood.

***Note*** If you want an n/a subaru manifold on your XT, you will need to buy a custom phenolic spacer that is 15.5mm in size. You may be able to use two 8mm spacers per side if you cannot source someone who can do this for you. The fuel rails will hit the avcs solenoids if you do not do this, meaning you will not be able to bolt the manifold down
 

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374 Posts
The n/a manifold flows way more than the turbo manifold. The n/a manifold is IMO, the best manifold ever produced for flow rate a linearity. It is much better than the new cosworth, magnus, and others...

Now, the catch...

These manifolds, if placed onto a turbo car, will actually hurt performance a little bit. They simply have too large of a plenum for such small turbos. They really dont start to shine, or become worth the hassle until you are running a 35r turbo or equivalent. When you start to dip into the 500WHP zone, this n/a manifold will be good for a 75-100whp gain up top.

Another god thing about the n/a manifold is the fact that it is a long runner design(No tgvs) and it utilizes top feed injectors(better).

If anyone decides to get one of these, please note that you cannot reverse it(to make fmic piping shorter) unless you want to gut the bracing on the hood.

***Note*** If you want an n/a subaru manifold on your XT, you will need to buy a custom phenolic spacer that is 15.5mm in size. You may be able to use to 8mm spacers per side if you cannot source someone who can do this for you. The fuel rails will hit the avcs solenoids if you do not do this, meaning you will not be able to bolt the manifold down
I fully agree with everything you said! That's why I fun them on every one of my builds except my daily. The only thing i would say is 75-100Whp might be a little high. I think more in the 30-50whp range.
 

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04 STi and Fxt
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169 Posts
I fully agree with everything you said! That's why I fun them on every one of my builds except my daily. The only thing i would say is 75-100Whp might be a little high. I think more in the 30-50whp range.
I have seen an HTA86 car make 75 from a ****ty *** cosworth...

Just sayin!
 

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2004 Subaru FXT MT
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1,853 Posts
so from reading this, if I got my hands on a intake manifold from 2.0 rex, get it pnp, i should have lil to no fit issues on my 2.5XT????
No, I don't believe so. Problem being the cable to DBW issue. I'm uncertain of the details to make it work...

No gain would be had doing this anyhow. If you aren't wanting down time, or are wanting topfeed injectors, go 06+ WRX/FXT/STi...
 

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Official sf.org decal guy
2006 FXT
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12,516 Posts
I have the intake manifold from a 2.0L JDM STi (cable throttle) in my 06 XT. The issue is that the angle of the manifold where the DBW throttle body mounts is different than the FXT manifold. The only way to get it to mount up was to have a custom adapter plate made. It was not cheap. The only reason I even bothered to have it done was because the shop that installed it had already installed the manifold and said it would have cost the same amount of money to have the adapter made as it would to reinstall the stock manifold.

The manifold look exactly the same, but A: it was already on and B: it's red.
 
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