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Old 09-29-2012, 12:37 PM   #1
mrchyes
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Default forced induction options

hello, I have a 2004 RS N/A with ~150k miles and just got the timing belt, headgaskets done...

I have no intentions of doing any kind of anything to this motor until i can absolutely afford it, in probably more than 2-3 years.
I was just wondering what the options for forced induction on a 2.5 SOHC N/A motor are. I heard about it from a friend and i guess i had just never thought it was even possible.

Flame suit on! hopefully i wont need it

discuss.
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Old 09-29-2012, 12:59 PM   #2
alt14
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Take a look at avo turbo kits for impreza n/a's or raptor superchargers
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Old 09-29-2012, 01:13 PM   #3
mrchyes
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will do thanks
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Old 09-29-2012, 01:20 PM   #4
poly_poly-man
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It will most likely be as expensive or more than a ej205 swap, and will give you less power and less reliability. Think long and hard about whether it's really your best option.
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Old 09-29-2012, 01:40 PM   #5
Patrick Olsen
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Quote:
Originally Posted by mrchyes View Post
I was just wondering what the options for forced induction on a 2.5 SOHC N/A motor are.
There's a forum for that.

Quote:
Originally Posted by poly_poly-man View Post
It will most likely be as expensive or more than a ej205 swap, and will give you less power and less reliability.
Way back in the day there were guys running turbo'd 2.5RSs (before the WRX came to the US) and making more power than the 2.0L WRXs. Obviously the tune has to be right, but if it is, more displacement and higher CR is going to give you more power.
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Old 09-29-2012, 07:53 PM   #6
mrchyes
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if i was going to do any kind of forced induction on this RS it would be because Id rather keep my first subaru and have more power, than sell it and get a new car with hidden problems.

That said, the reason id rather go with a RS block and sohc and the higher compression of the RS motor is because i was told higher compression and sohc is better for forced induction.

Is that true? or no?

would it be better to go with a stock STi engine?

maybe i am led astray that the RS 2.5 is better for forced induction power, it seems like it doesnt make sense, but idk.
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Old 09-29-2012, 08:57 PM   #7
chazly413
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The RS engine is not designed for boost and the STI engine is. I think that's all you need to know in terms of which would be the best overall setup.
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Old 09-29-2012, 08:57 PM   #8
James2.5i
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Is this your DD?
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Old 09-29-2012, 09:27 PM   #9
mrchyes
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i am looking at this question in the stand point of the future, in the future this RS will not be my DD, probably a project car. i guess it is too broad of a question to ask, but if the RS engine isnt designed for boost then how have people done it reliably?
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Old 09-29-2012, 10:41 PM   #10
alt14
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Well what they're saying is that the rs wasn't originally designed with forced induction in mind, therefore no reason for reinforced materials for reliability, however they can be boosted at low pressures and be reliable from what I hear though I wouldn't trust it myself
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Old 09-29-2012, 10:56 PM   #11
mrchyes
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well, i was just wondering thanks for all the info guys..

i guess when the time comes to rethink the engine i will have to decide then
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Old 09-30-2012, 11:29 AM   #12
James2.5i
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You can reliably do it (within reason of course, 20PSI turbo may be more than what your car can handle long term), but as a DD you'd have to have a backup for when things go wrong, money needs to be saved, or mods take longer than expected.

As a project car though, you could garage it for as long as you want until it's ready. And as long as you keep the psi reasonable, you can reliably upgrade to a turbo or supercharger application.

Is it tuned at all now? You'd be surprised at how a tune can improve a car's performance. Maybe worth looking into?
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Old 09-30-2012, 01:46 PM   #13
mrchyes
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a tune is definitely worth looking into i will probably have headers and an intake soon enough and might flirt with the idea of going to E85, idk what the gains would be, but ive never seen E85 run on a N/A scooby.
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