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Registered
2015 ; 2.5i ; 15,000 Miles (I drive a lot less than I used to !!!!)
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144 Posts
hi
the setup you have now from the factory is best you will not gain anything and just wasting money and destroy perfectly working part remember engineers have done all the work for you so save yourself money and headache and leave it alone and get something with turbo
Get "something" .... probably a blown engine ... and I do not mean as in with a "blower" .... !!!!! It is a well known fact that an engine that "breathes" better also performs better ! Both Intake air restrictions & Exhaust fume restrictions limit engine performance at both mid-range, and at top-end RPM's: but if you want to have Low-End drag-racing capability at every Red-Light that you can find ... then the Turbo is the way to go !!! But ... that Turbo will come with the early, and often ... replacement of engine(s) via Rod-Bearings, Oil-Consumption, Head-Gaskets ( !!! ), and even possibly a tranny or two: That "opinion" comes from over 60-years of engine experience ..........
 

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2018 Forester XT Touring HT-CVT
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615 Posts
Fun fact...the orange filter from the XT engine also fits the NA 2.5 engine. It has a lot more pleats but is still Subaru spec and will fit the air boxes for both engines. So it's worth a try if you want to increase airflow in the NA 2.5. Best of all, they basically cost the same thing too!
 

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Registered
2006 Forester
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82 Posts
I treat my NA 2.5 to a new pleated dry AF every 5000 mi. Because it is not about increasing air flow on a NA motor, it is about not letting a dirty filter decrease air flow. Also it is DIY and cheap. Or you could vacuum a fairly clean AF, as well. But why bother? To postpone spending a few bucks for a few months?

It is possible to increase power on a NA 2.5. On the whole it is not worth the effort and cash. There are specific inexpensive changes that would increase efficient delivery of power to the road so that the car performs as if it had more HP. You can read about them here:

 

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Registered
2015 ; 2.5i ; 15,000 Miles (I drive a lot less than I used to !!!!)
Joined
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144 Posts
I treat my NA 2.5 to a new pleated dry AF every 5000 mi. Because it is not about increasing air flow on a NA motor, it is about not letting a dirty filter decrease air flow. Also it is DIY and cheap. Or you could vacuum a fairly clean AF, as well. But why bother? To postpone spending a few bucks for a few months?

It is possible to increase power on a NA 2.5. On the whole it is not worth the effort and cash. There are specific inexpensive changes that would increase efficient delivery of power to the road so that the car performs as if it had more HP. You can read about them here:

There is a lot to be digested from all these details : bottom line - it is hard to out-perform multi-million-dollar corporate Engineering-Resources, and even harder to do the same for their production capability ! About the only time that John-Q-Owner can beat them is when they have tripped up with a really dumb design, or production process; but when that does happen, critical-oriented-owners can and do make impressive improvements ! That requires a lot of both mental and physical effort, and is seldom worth the Cost/Return evaluation; usually most changes carry significant short/long-term ramifications against such moves ! Like stated near-by; it is so much better to just keep the original design as optimum as possible by top-notch owner maintenance practices ..... //// !
 
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