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While looking at my buddy's '05 STi engine the other day I noticed that his airbox has a much larger intake duct than my FXT does and it got me thinking about the induction differences between the two cars.

Many STi owners will tell you that a CAI doesn't add power until you get larger than a VF39 while others argue the CAI does make power. If the FXT box is more restrictive than the STi box surely VF39'd FXT owners could benefit from a good intake like a K&N or APS :confused:

Anyone ever do a dyno comparison? A good intake should also help with spool up :drive:
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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Same airbox, the part from the fender by the headlamp to the silencer (hole in the fender) is not the same though. What you are calling the intake duct. That should not make much difference in the restriction though. The real restriction is in the silencer. The airbox is pretty much the same from early on at least the motors that have an MAF.

look here:

http://www.scoobymods.com/forums/showthread.php?t=4475

I've attached a pic of the thing that lives in the fender.
 

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Discussion Starter #3
Peaty said:
http://www.scoobymods.com/forums/showthread.php?t=4475

I've attached a pic of the thing that lives in the fender.
:wtfeyes That creature from the fender is a very ugly beast! IIRC none of the STi guys have been able to prove a power gain from removing the silencer so unless you like noise this might not be a great mod :?

My guess is the K&N or APS intake would add a few HP and help the turbo spool faster. Anyone running one of these?
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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Peaty said:
removing the silencer makes the intake a CAI because it's cooler in the fender than from behind the headlamp where the F-XT gets it's air.

I've used a green filter

http://www.scoobymods.com/forums/showthread.php?s=&threadid=2271

with the silencer removal and now have a cobb short ram:

http://www.scoobymods.com/forums/showthread.php?t=5530

Other than the noise I don't notice much of a difference.
Thanks for the info. I assume your FXT is still running the stock turbo? If so this would have a large impact on the airflow needs, and therefore effectiveness, of a CAI on your car. Those of us with full TBEs, tunes and VF39s (or larger) might see some good gains from a free-flow intake.
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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Currently running stock turbo with: Cobb Stage 2, Cobb Up pipe, Cobb turbo-back and Cobb Short Ram in take. I'm running mid 13's in the 1/4 so I'm happy with what I've got at this point.

I know there is a lot of debate on the need for a CAI on a turbo. But I've seen the math on, but don't have it in front of me now, CAI's. A turbo charger has a set amount of temp increase across it and the IC has a set amount of heat it can pull out. For the most part colder in colder out to the motor. To me a, CAI will not get you more power but it will be a power loss avoidance. Mostly during stop and go situations. As you can see by my temp graph in the short ram link, when moving, a short ram gets amb temp anyway. There is a guy out here with a 4-wheel dyno, and he does nothing but tune with it all the time. He'll tell you that the stock intake is very good and he's seen losses or funky data with most everything else. I've read that to 400 hp or so the stock intake is fine.
 

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The Modfather
2019 Impreza 5dr Sport - Manual
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Yes that's the snorkus aka silencer
 

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Our stock intake will not support a green turbo. I had the green, stock box, "green" drop-in filter and snorkus removed. I couldn't make over 14 psi. When I pulled the green filter out, boost shot up. That's all I did. Opened the box, pulled the panel filter out, put the box back together and went for a spin. Boost shot up to the target 19 psi.

This could indicate a limitation of the green filter more than the box itself, but unless you go with a foam dropin which might work, the box/dropin filter is a restriction.

Frank
 

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“The Thing That Lives in the Fender” came out in 1958, starring Vincent Price and Raymond Burr. If you look closely at the credits you will notice a (then) unknown actress named Kim Novack. She plays the girl half of the couple who get eaten early on. If I remember right, there was a 3-D version, but it didn’t see wide release.
 
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