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Guest Message by DevFuse

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Cold Air Intake for $8.13?

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5 replies to this topic

#1 2.5_IMP


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Posted 02 March 2009 - 08:10 PM

I was getting tired of looking at all the air intake junk under the hood of my 2002 Outback Sport, so I decided to research cold air intakes. There was no way I was going to spend $250-$300 on the offerings from AEM, Injen, or Cobb. I looked at the Ganzflow intake, but $129 is steep for a 3" bent aluminum tube and some silicone couplers. I figured I could make something similar out of 2" PVC pipe from Lowe's, and I set my budget at $10.

So, I pulled out all the stock intake junk, except the airbox/filter, took some measurements, and drove to Lowe's. The following is what I bought:

(1) 2" x 2' black PVC pipe $2.17

(1) 2" flexible coupler $4.43

(1) 2" 45 degree street elbow $1.53

After some test fitting, I found that I wouldn't need the full 2' of pipe. I took a hacksaw, and cut a few inches off the pipe at a 45 degree angle.

The coupler had to be stretched to fit over the piece of pipe on the air box, as the ID of the coupler was roughly 2.5", and the OD of the pipe was 2.75".

I used the 45 degree elbow, because I wanted the intake to go into the first hole in the fender, since that is where the regular intake gets air from.

The finished product:

Posted Image

Posted Image

Posted Image

I should mention that the engine is MAP, not MAF. Read why this matters here:


I'm going to take the car out tonight after I reset the ECU, and see how my new intake does.

Thanks to Larry Ganz for the idea.

I was going to post this on NASIOC in the N/A forum, but I figured USMBers would appreciate it a bit more.

#2 The Dude

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Posted 03 March 2009 - 08:27 AM

Subaru engines are very effecient and fully tuned right from the factory. There is very little that can be done to a Subaru engine to significantly increase HP that does not entail great effort and expense.
Did you know that the "stub" on the "junk' you removed actually was engineered for a specific purpose? I understand the urge to hop an engine. But a Subaru engine, like many Japanese engines, is already churning out very close to the maximum HP.

#3 2.5_IMP


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Posted 03 March 2009 - 11:21 AM

Yes, Subaru engines are very efficient and tuned right from the factory. I have no illusions of increasing horsepower by doing this, nor did I mention that this was my intention. I realize all the "junk" has a purpose. On a 2002 Impreza with a MAP sensor, most of it is there to quiet the intake noise.

What is this "stub" you speak of? And what specific purpose is it engineered for?

Although there is no noticeable power gain, the annoying, high-pitched whistling sound when I accelerate has been replaced by a low, throaty sound. This alone is worth $8.13.

#4 abog


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Posted 03 March 2009 - 11:55 AM

Good job....what did you do for an air filter? It is stuff like this that is keeping the hot rodder mentality alive. I love it.

#5 greenleg88


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Posted 03 March 2009 - 02:00 PM

Good job....what did you do for an air filter? It is stuff like this that is keeping the hot rodder mentality alive. I love it.

the airfilter is moved to hook up directly to the manifold. so it looks like that pvc pipe leading into the fender is just pulling air from the fender.

#6 2.5_IMP


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Posted 03 March 2009 - 05:00 PM

The air box/filter is in the stock location. The pipe goes into the fender hole an inch or two. There are small air scoops on the front of the bumper that bring cold air in the the fender well. I was going to make the pipe go all the way down to the vent, but I don't want to suck up water/mud.

The only thing I've added since the photos is small piece of rubber where the pipe goes into the fender, as there was some vibration/noise from the pipe touching the sheet metal.

The acceleration is a bit quicker, and LOUDER. There is so much road noise due to the cheap interior, so a little extra noise from the intake doesn't bother me.

I wish I had taken a "before" picture, to show what the stock intake looks like.

Thanks for compliments, and if anyone sees any problems with this setup, I would appreciate knowing them. I am just a know-nothing hack.

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