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Old 08-18-2012, 11:23 PM   #1
Charlton
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Default Who Likes the Stock Air System on their Subaru?

I've put intakes on Subarus in the past and they sound good but I never saw any real benefit.

Who likes the stock airsystem on their Subaru? I think it is a good design on my 2002 Forester S. There is a large air reservoir behind the throttle that gives me solid low end torque but I can still get good acceleration.

I've found intakes hurt power in the powerband where I spend most of my driving. They only help when I'm smashing down the pedal which is rare. I'm not a race car driver lol.
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Old 08-19-2012, 03:20 PM   #2
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They really do not accomplish anything. The stock intake is fine.
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Old 08-19-2012, 09:24 PM   #3
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I feel the same way. I tried the hybrid setup and since most of my driving is in the city and below 3600 rpms, it made me appreciate the stock intake more. I don't think the heatsoak issue made it any better. That aluminum pipe would get so hot, and stay hot for quite a while. I wonder how high it was raising the intake temps?
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Old 08-19-2012, 09:26 PM   #4
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Quote:
Originally Posted by Filthy_Mchaggis View Post
I feel the same way. I tried the hybrid setup and since most of my driving is in the city and below 3600 rpms, it made me appreciate the stock intake more. I don't think the heatsoak issue made it any better. That aluminum pipe would get so hot, and stay hot for quite a while. I wonder how high it was raising the intake temps?
Probably not very noticeable. The air is moving through there so quickly it has little time to be warmed.
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Old 08-19-2012, 11:20 PM   #5
Charlton
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I looked my stock intake on my 2002 Forester this evening, same intake as the Impreza RS. It looks like a very goood system. The source of air is right behind the passenger side of the front of the car. This is a good source of "fresh air". The polymer material of the factory tubing IMO does a better job of absorbing heat than some hot aluminum tubing with some Asian prostitute marketing advertises. Immediately behind the throttle is a large air reservoir with a filter. This gives the engine a mouthfull of air vs the "tube".

Look it over sometime, it's actually a very good system since it pulls air from the coolest part of the engine bay without the risk of sucking in water, absorbs heat, and filters air immediately behind the throttle.

Go Subaru!! Thannk you for giving us an excellent intake from the factory : )
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Old 08-19-2012, 11:44 PM   #6
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The stock intake is not restrictive at all. I mean 0% and I mean zero percent. There is no point to changing out the intake. There can be a gain, but it requires a different ECU tune. Not doing so will actually lose power in the midrange. It requires a tune to get that midrange back. Then the actual gain comes from being able to pull in colder air than stock. If you can't do that, you're not gaining. You can't gain any top end with any intake change, any. You can only lose midrange, a sizable amount too, 20 or so ft-lbs.
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Old 08-19-2012, 11:53 PM   #7
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Have you forgotten about the hybrid intake thread? In the very first post, you can plainly see that the stock intake on 05-07 (and probably beyond) is not perfect from 4000-6500rpm.
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Old 08-19-2012, 11:53 PM   #8
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Quote:
Originally Posted by Back Road Runner
The stock intake is not restrictive at all. I mean 0% and I mean zero percent. There is no point to changing out the intake. There can be a gain, but it requires a different ECU tune. Not doing so will actually lose power in the midrange. It requires a tune to get that midrange back. Then the actual gain comes from being able to pull in colder air than stock. If you can't do that, you're not gaining. You can't gain any top end with any intake change, any. You can only lose midrange, a sizable amount too, 20 or so ft-lbs.
Agreed...from my experience aftermarket intakes decrease performance unless I live at the race track lol! Swap paper filters every other oil change and have fun : )
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Old 08-20-2012, 10:02 PM   #9
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The best design would be the stock layout/dimensions with a smooth, mandrel bent tube in place of the molded plastic with accordion ribs to allow flex. It just so happens that someone had already thought of that and shared it with the world years ago. Logging provides data that supports the theory that it makes small gains in the areas that need it most and liars nothing anywhere.
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Old 08-20-2012, 10:52 PM   #10
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^ This.
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Old 08-21-2012, 08:22 AM   #11
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Stock is the best for our cars, hell even for the majority of LGT/WRX/FXT/OBXT/STi's
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Old 08-21-2012, 01:15 PM   #12
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Guys what about map sensor cars . My friend has an impreza with a map and he has an aftermarket cai and he said its very nice and much improved throttle response but i dont know why do cars with map sensor would benifit from a cai while others with maf dont
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Old 08-21-2012, 01:26 PM   #13
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It's not that MAP-equipped cars benefit more from it, they just don't get the negative effects that an aftermarket intake puts on a MAF-equipped car. All of this conversation about hybrid intakes and rich down low and all the bad stuff associated with intakes is only for MAF-equipped cars.
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Old 08-21-2012, 01:53 PM   #14
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I've tried the hybrid on my old MAF based '95. Didn't do crap... and it was an AEM SRI to the stock airbox. Left my '98 OBS stock with a drop in filter.

Now... my dad's '04 Forester MAP... totally different story. The Ganzflow replica made a nice sound difference and it has an actual growl to it now... for $30 shipped. Hopefully MPGs increase... that's what we're shooting for now.
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Old 08-21-2012, 06:38 PM   #15
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Quote:
Originally Posted by chazly413
It's not that MAP-equipped cars benefit more from it, they just don't get the negative effects that an aftermarket intake puts on a MAF-equipped car. All of this conversation about hybrid intakes and rich down low and all the bad stuff associated with intakes is only for MAF-equipped cars.
Yea so u mean both on both map and maf they dont provide real gains but on maf they might decrease performance while on map performance isnt hurted right ? However i've read that the cobb sri which goes into the fender provided good gains for map .Btw i have another question do a better throttle response always means more power or not always . Thanks
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Old 08-21-2012, 09:52 PM   #16
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From my experience the increased sound of the throttle is what makes people think they are getting more power. At least that's what I thought when I had an injen CAI on a 98 Legacy GT.

Drop a fresh, quality paper air filter in a stock NA Subaru and floor it. It might not be as loud as an intake but it will have better low end torque to get you moving and excellent high RPM performance. Can anyone really tell a 6 hp difference? The stock design on my 02 Forester is very good. It keeps a large supply of filtered air immediately behind the throttle and it pulls air from the front of the engine behind the passenger side head light.
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Old 08-21-2012, 10:01 PM   #17
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Quote:
Originally Posted by Charlton View Post
From my experience the increased sound of the throttle is what makes people think they are getting more power.
The placebo effect strikes again.
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Old 08-21-2012, 10:08 PM   #18
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The airbox and/or tq box it's not an air reservoir ready to open the gates on demand, it's a way to transition from a smaller diameter pipe to a square box with relatively even flow across the filter. The shape and volume may have some beneficial resonant effects, too.
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Old 08-21-2012, 10:15 PM   #19
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A lot of people just toss CAIs on their cars because they don't have enough experience to do other modifications, it's inexpensive, and their basic understanding is that factory airboxes are restrictive and that CAIs help them "Breathe" better.
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Old 08-21-2012, 11:28 PM   #20
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Quote:
Originally Posted by RaceFaceXC
The airbox and/or tq box it's not an air reservoir ready to open the gates on demand, it's a way to transition from a smaller diameter pipe to a square box with relatively even flow across the filter. The shape and volume may have some beneficial resonant effects, too.
This is a good explanation. It does help with low end torque in my experience.
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Old 08-23-2012, 04:52 PM   #21
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I've been reading a lot on the subject, and the stock intake system is best for all around performance...

Except for reducing intake temps. My Saab 92x 2.5i had the stock air inlet in the engine bay. After reading the williarty write ups here I was going to build the whole hybrid intake. With a scan gauge I noticed the stock intake temps would always skyrocket in traffic or after the car being parked on errands (140+ degrees) sapping power.

Then I added a used WRX style inlet horn and didn't see much improvement. In fact the temps really went south. The horn does not fully match the 2.5i snorkus so I taped it up. Still no improvement. Then I noticed two things: without the proper mount the WRX inlet sat on the radiator and in stock WRX the inlet is sealed off so it does not pull under hood air and pulls high pressure air from in front of the radiator.

Got a used WRX snorkus and a new lower hood seal from Subaru. The WRX snorkus is about 0.2" larger in diameter on the air box side (still shoe horns in!) and matches the inlet horn. It also lifts the angle of the horn to push it up against the lower hood seal and hold it off the radiator.

Problem solved! My intake temps never are over 120 in traffic or after being parked and they cool to 4-8 above ambient after a minute or two of driving. Stoplight to stoplight I have more power and a quicker throttle, it never feels heat soaked anymore.

More power, probably not much, but greater drive ability in getting the power that should be there.

Also the engine growl is pleasantly noticeable (I never heard it before) and everything is OEM. Total price: $35 in used and new parts.

Im so happy with it I may forego the rest of the hybrid.
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Old 08-26-2012, 11:24 AM   #22
Counterfit
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You can put some heat reflecting material around the new tube, or use ABS piping.
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Old 08-26-2012, 12:39 PM   #23
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I just replaced the stock snorkus on my OBS with a 2.5 frankenmotor and eliminated all hesitation I've been trying to diagnose for awhile now. D'oh!
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