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Discussion Starter #1
It would seem that 'someone' would be testing out exhausts for what works best, what sounds best and whether or not CAI's are a good or bad thing.... ya know... crunching the numbers with data logging and what not.

I am 'all new' to the Subie world.... but not to the offroad and performance side of things.

Just curious as to what is out there......
 

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Technically, most stock Subaru intakes are "cold air intakes".

As for any performance upgrades via intake and exhaust... well, for the 4th generation Impreza the best I could find was this...

STI's Japan-only catalog:
http://www.sti.jp/parts/catalogue/impreza_gjgp/index.html
The parts listed on the Japanese site do apply to the same exact chassis designation (GP, indicates Impreza 5-door hatch), however certain things will not fit due to the differences between the XV and the regular Impreza.

In summary, the sole power-related bolt-on upgrade available in Japan only is the STI exhaust. Though historically, exhaust upgrades for Subaru's soft off-roaders requires a different mounting setup from the non-lifted Subaru vehicles.


In general, stock Subaru intake systems do a decent job of keeping water out of the air intake. As for exhaust, I would simply have a reputable shop make a custom-exhaust suited to your local area's laws and your personal tastes (aesthetics and/or performance).

Usually the turbocharged Subaru vehicles get much more attention from the performance aftermarket.
The non-turbocharged Subaru vehicles can often be found without any available upgrades, so the best you can do is do a custom-job on everything you want to do. We're probably not going to get much from the aftermarket for performance parts.

What I'm hoping for from the aftermarket aren't necessarily power upgrades, but a clutch upgrade. A higher-torque clutch with a clutch plate that has a higher heat resistance would perform better for off-road use.


Honestly, some of my upgrades for my future XV when I do get it and then drive it past the warranty period (regarding power and drivetrain) would be:

* upgrade clutch
* head port and polish
* custom camshafts
* custom engine management with custom tune
* high-flow air filter (NOT an oil type! DRY type)
* custom retrofit STI or Bosal muffler (axleback)


Sadly, it's extremely expensive to get any kind of extra horsepower or torque out of a naturally-aspirated Subaru engine, especially considering it's not a very big market at all.
 

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Discussion Starter #3
Thanks for the response. I was just curious on a few areas and you headed them up for me. I never expect a whiplash affect from cai or exhaust.... Just a slight bump if anything.

Having the CVT is something I tried to "hear" in my head with an upgraded exhaust and not sure I like what I heard..lol.(unless you use the paddle shifters)

Some vehicles benefit from cai's and some don't because the engineers did it right from the start.
 

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Xtrekr said:
Thanks for the response. I was just curious on a few areas and you headed them up for me. I never expect a whiplash affect from cai or exhaust.... Just a slight bump if anything.

Having the CVT is something I tried to "hear" in my head with an upgraded exhaust and not sure I like what I heard..lol.(unless you use the paddle shifters)

Some vehicles benefit from cai's and some don't because the engineers did it right from the start.
From an engineering standpoint, the CVT is the superior transmission but...

listening to a CVT do its job just isn't something all that fun. Though it is trying to stay within certain RPM ranges, it doesn't make for great engine music :-\
 

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Discussion Starter #5
That's what I figured. Lol. Thanks
 

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Subaru has these intakes pretty dialed. Take for example the intakes on the newer WRX and STI. All the aftermarket companies have found that the only way to gain more power with an intake is to use larger diameter piping, which obviously requires a tune because the larger piping changes the MAF calibration. There's a reason that SPT does not offer an intake for the newer model WRX/STI, you can't just bolt on new piping and get more power with these cars. Assuming Subaru put similar R&D into the NA engine, which I'm sure they have, they have pulled every bit of power they can from these motors.

Exhaust also isn't going to to anything in the form of a cat back, all that's doing is picking which sound you like (if you go too large piping you may actually result in a loss of power). Removing the cats and getting new headers may net gains but only if the engine is tuned to maximize those gains. Again, the R&D money Subaru has is insane and they put it to good use. Exhaust flow is like water in a straw. Too small and it goes fast but you're not moving much, too large and the volume is high but the flow rate is low. What they are trying to achieve is a balance between velocity and volume. The goal is to have enough velocity (without compromising volume) so that when the valves overlap the exhaust velocity is actually helping pull air into the cylinder by creating a vacuum in the exhaust as the gasses are expelled. Obviously the function and design of the exhaust on a turbo or supercharged vehicle is different.
 

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Discussion Starter #7
Well stated... Good insight. Thanks
 

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I do this whole Subaru Performance thing for a living so I've been pretty well versed in it all. I'm just here to help where I can!
 

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AWDfreak said:

Honestly, some of my upgrades for my future XV when I do get it and then drive it past the warranty period (regarding power and drivetrain) would be:

* upgrade clutch
* head port and polish
* custom camshafts
* custom engine management with custom tune
* high-flow air filter (NOT an oil type! DRY type)
* custom retrofit STI or Bosal muffler (axleback)


Sadly, it's extremely expensive to get any kind of extra horsepower or torque out of a naturally-aspirated Subaru engine, especially considering it's not a very big market at all.
I take back what I said about this... because it would require having me or a shop custom-design and re-engineer the FB20 longblock with custom connecting rods, pistons, crank, etc optimized for performance. With upgraded heads, valvetrain, exhaust, etc, the stock engine internals would not be tuned for optimal use of the upgrades.

At that point, one would be better off swapping in an FA engine rather than the economy-minded FB engine. I guess I could dream of making a custom performance built FB engine in the far future, but it's nothing more than a novelty than something that actually has any real performance benefit.
 

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Discussion Starter #11
Dream on my friend..... DREAM ON!!!

Nothing wrong with it..... it keeps our minds active and our hands busy when we put thought to reality. I'm a fabricator and love to dream up junk.. I do it daily at work and at home. Most of the time, when we get new equipment at work, a few of us will go through the system, see improvements that can be made.....tear it apart and rebuild it better! We love it!!!
 

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Discussion Starter #14
Great info spyder720... Thanks!!!


Sent from my iPhone 4s using Tapatalk
 

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I haven't had the chance to really look all too in depth on this, but how different is the XV exhaust setup in comparison to the 2012 impreza? if products have already been made for this vehicle, even if its just the muffler and not the rest of the piping, you could presumably bolt them onto the XV right?
 

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I would imagine with the lift of the XV, it'll be different enough to the point where it won't fit. (Same thing with the Legacy and Outback, exhausts on the Legacy don't fit correctly on Outbacks) But I hope not...
 

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Subi-roo.... Subi-genius. Excellent explanations, as always.
 
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