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 Post subject: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 9:07 am 
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Posts: 259
Location: Melbourne, Australia
Anyone changed over their manifold with an sti red one? Ive got one from a 2011 sti and I was reading they flow better. Is it a bolt on like for like job?

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Note: Ha, moving to Melbourne for good next month, cant wait to see your Foz on the road Tobyo, ill keep an eye out for it.


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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 10:02 am 
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I Say: There's no 'i' in Team, but there is in Winner!
Vehicle: MY10 XT

Posts: 1967
Location: Mealbun Orstraya
They are also a much better heat sink that plastic. You would have to change your turbo, intercooler, piping etc. You would be far better just upgrading the turbo if you want any noticeable results.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 11:09 am 
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Vehicle: MY08 XT (SH)

Posts: 1535
Location: Brisbane
On the topic of heat only, are you talking about:-

(a) heat in the runners from being connected to the engine; or

(b) heat from the post-intercooler inlet charge.

I would have thought that (a) would be the main reason for the inlet manifold to heat up and that metal runners would be counter-productive to a cool inlet charge.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 1:43 pm 
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I Say: There's no 'i' in Team, but there is in Winner!
Vehicle: MY10 XT

Posts: 1967
Location: Mealbun Orstraya
The STI intake runners would be great in re heating the post cooler air. A good heat sink for the engine bay. Never heard of issues with the plastic manifold, so not sure of the science behind the aluminum manifold.
Would be good to get hold of someone local in Vic S/E to take a thermal image of their aluminum manifold to compare to mine.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 3:17 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17936
Location: Spearwood Perth WA
There has to be a good reason why Subaru kept the aluminium manifold on the STi model, yet moved to plastic on all the other turbo models. (Wrx, XT etc...)

One can only guess the aluminium manifold is the preffered option for performance, as it is used on the premium performance orientated sports offering of the subaru range.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 3:36 pm 
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I Say: There's no 'i' in Team, but there is in Winner!
Vehicle: MY10 XT

Posts: 1967
Location: Mealbun Orstraya
Interesting that so many high end sports car manufacturers use plastic manifolds. Im guessing a bright red plastic STI intake manifold would look rather nauseating.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 4:01 pm 
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Vehicle: MY08 XT (SH)

Posts: 1535
Location: Brisbane
Bram wrote:
There has to be a good reason why Subaru kept the aluminium manifold on the STi model, yet moved to plastic on all the other turbo models. (Wrx, XT etc...)

One can only guess the aluminium manifold is the preffered option for performance, as it is used on the premium performance orientated sports offering of the subaru range.


My little unsupported theory on all this is that:-

(i) the older style manifold (with downward-flowing intercooler) with central throttle body position probably distributes air between cylinders more evenly than the offset-throttle plastic manifold (with side-flowing intercooler);

(ii) the STI skunkworks tends to hold on to older style engines a lot longer than the rest of Subaru on account of the development work already put into them.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 4:17 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17936
Location: Spearwood Perth WA
Yowie wrote:
Bram wrote:
There has to be a good reason why Subaru kept the aluminium manifold on the STi model, yet moved to plastic on all the other turbo models. (Wrx, XT etc...)

One can only guess the aluminium manifold is the preffered option for performance, as it is used on the premium performance orientated sports offering of the subaru range.


My little unsupported theory on all this is that:-

(i) the older style manifold (with downward-flowing intercooler) with central throttle body position probably distributes air between cylinders more evenly than the offset-throttle plastic manifold (with side-flowing intercooler);

(ii) the STI skunkworks tends to hold on to older style engines a lot longer than the rest of Subaru on account of the development work already put into them.


I had also thought the move to plastic was an effort to reduce production cost. EG, its less expensive to mould a plastic manifold, than it would be to cast an alloy one. But then that theory doesnt hold true when you look at the NA EJ engines, which still used the cast alloy NA types, even after production of the plastic turbo ones had begun.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 4:29 pm 
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I Say: Car mods are like OddBodz, you got to collect them all! -------------------------------------
Vehicle: MY05 STi swapped sled

Posts: 17936
Location: Spearwood Perth WA
Tobyo wrote:
Interesting that so many high end sports car manufacturers use plastic manifolds. Im guessing a bright red plastic STI intake manifold would look rather nauseating.

That is a trend that is not specific to performance cars though. Practically ALL Japanese and Euro consumer vehicles use plastic manifolds these days.

Look at ford and mazdas for example, like the mazda 2/3, and focus/fiesta and stuff like that. They arent just plastic manifolds, pretty much the entire front ends are plastic aswell. No longer do cars even have metal for radiator supports and such hidden under plastic bumpers. Now a days, its plastic everything. Before long, i think we will be seeing plastic/composite body shells aswell.

I **** hate it.

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 Post subject: Re: Sti manifold to replace plastic manifold on SH Foz
PostPosted: Sun Jan 06, 2019 8:31 pm 
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Posts: 259
Location: Melbourne, Australia
Apparently the sti manifold flows better, but if the changeover process is huge then it's probably not worth the effort.

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Note: Ha, moving to Melbourne for good next month, cant wait to see your Foz on the road Tobyo, ill keep an eye out for it.


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