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I used the recipe for a homemade airflow and it works. (not that i'm surprised of course!) Anyways, I wanted to share my mods because I did run into a dilemma. I went to the store looking for 3" PVC pipe, elbows, and 3" to 2.5" adapter coupling. I found all but the coupler. Due to that, I ended up having to downsize everything to a 2" pipe, etc. I still have better performance and increased "throatiness" - if that's a word. Basically, it looks funky but it sounds and performs great.

The only problem I have is that it seems that my gas mileage has decreased.

I reset my ECU right after the install because I didn't want it to be confused with the new air intake.

Does anyone have any ideas??
 

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it sounds and performs great. The only problem I have is that it seems that my gas mileage has decreased.
uhhh---could there be a connection? are we enjoying the sound more than we realize? could it be that by time we hear induction noise, we're accelerating hard enough that mpg is gonna suffer? just wondering. :D

i also ended up going with the smaller diameter PVC-CAI, and agree it seems to work fine. i do plan to replace with one made of 3" pipe and will note any changes i see.

my fuel mileage increased slightly with just the CAI. once i added the WRX pipe and REALLY started enjoying the audio track, it definitely suffered a bit. i suspect once the new toy factor wears off, that it will actually improve it.
 

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that is my thought also. I actually found a thread on scoobymods that details the 3" design. I think I may try that tonight. Do you think that there is a need to reset the ECU or will my car learn on its own?

cpt...I agree with the fun factor. I have been pushing my car a bit harder since the install. I haven't even really tried to give it more - I just feel like the car accelerates smoother and faster. I will let you know after I do the install tonight.
 

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It is not hard to do, matter of fact, I will have a 4' peice of leftover PVC tubing. I already have like 4' of the 2" PVC but I am trying the 3" tonight so back to Home Depot for the 3" pipe. Anyways, I will have the extra length laying around so instead of wasting the $5, you can have that if you are interested.
 

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who needs a kitchen sink anyway?
where am i SUPPOSED to wash parts...??

Steve, PM me yr email address and i'll send what fotos i have.

you'll like result if you do this to yours. esp for the $....that's half the fun, doing for >$10 what some folks spend $200 on....
 

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this seems pretty simple and would really make your car stand out....just rotate the CAI upward and bust out the hole saw to cut a hole in the hood, and you're all set to ford those croc infested rivers....:D :D
 

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Very funny, my long term goal is to have an intake that actually goes out the fender or so with a fiberglass piece to 'catch' the air!! He He. Let's go snorkeling. Brian
 

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nice call- haha Well, I didn't get a chance to install the 3" but I will try again tonight weather permitting of course!
 

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Ok, someone (brian) answer questions for me plz!
I guess I thought I understood all this until I really started to think about it.

Here is a pic of my stock intake:


Here is the same pic with some pretty colored boxes:
Blue, Green, Orange, Yellow, Purple...


Tell me if I'm correct:
Blue: Connects to the front of the right fender panel, directs colder air from fender to "radiator area"...
Green: Stock airbox, takes air from the fender panel, through the filter.
Orange: MAF Sensor box, checks air temp, pollutants, etc...
Yellow: Just a tube to connect to the purple box...
Yellow Dotted: I have no idea what the purpose of this phallus is...
Purple: ? Builds air pressure before entering the engine? I dunno.

If possible, give more detailed descriptions of what each color section does, and of course, correct my mistakes.

My main question is...what would be the point of me doing a HomeDepotCAI setup here? Isn't my engine already sucking cold air from the right fender? Also, when doing the cheap CAI, what happens to the air filter? I'm sure you don't run without a filter, but I don't understand how you stick one into a chunk of PVC pipe.
And seriously, what's with the phallic dotted yellow part?!?!

Thanks in advance. Hopefully this will answer questions for more people who are confused but afraid to ask.
 

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FMGreen said:
Yellow Dotted: I have no idea what the purpose of this phallus is...
Purple: ? Builds air pressure before entering the engine?
Yeah. That appendage is a curiosity to me, too. When I saw it in my "new" '04 I thought something was missing there. It points downward, whereas it appears yours is out to the side (thank goodness this is talk of a car part here!). :D

I expected it to be the usual warm/hot air intake, piping in from off of the exhaust manifold, like that of typical carburated engines. Seems that things are very different for fuel injected engines, and this being my first I haven't a clue how things work.

Must be some form of air warming device to prevent ice buildup during the inflow of the fuel/air mix.

Purple box is just the air filter housing, in mine anyway.

I've wondered about these "cold air intakes" being talked about. Seems some people use a K&N cone filter on the end by the fender, others just use a pipe, still going into the fender, and keep the original filter box. I just don't understand how the MAF can be bypassed without ill effects.
 

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Well, nice pic there Greeny. The yellow dotted appendage is a Subaru Engineer marvel. It is there to prevent the low end torque loss by providing an extra storage area for air in case it is needed. No crap, that's it! That is what I have read about it, it's there for air to be readily available to the engine, like a small storage area. Oh, and you have a MAF based engine so building the CAI would have to include the sensor section in orange.
Phase 1 engines like yours are MAF based, while the newer engines don't have the sensor inline in the intake plumbing. You could try and build one that works for you, but Cobb had just finished theirs a couple of months ago with a lot of R&D of how to get one to work right. Your shot. Brian
 

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Oh come on guys, I go offline for half a day and you're posting about storing air in a phallus...

We have covered this information before. The mystery tube is an intake noise supression device. Look up "Helmholtz" for more information.

Here's a good basic description:
http://www.autospeed.com/cms/A_1969/article.html

And one that is far more technical:
http://www.mecc.unipd.it/~cos/DINAMOTO/risuonatore/risuonatore.html

As for the last component, it's called a plenum. Browse this:

http://www.dune-buggy.com/turbo/intake.htm

...including some of the links at the bottom.

Here's my 98 engine bay:
http://www.subaruoutback.org/photopost/showphoto.php?photo=1224&papass=&sort=1

(I have no idea why the collision shop wrote "under hood" on the bottom of the scoop plate...):rolleyes:

You can see the intake at the top right side of the radiator - this leads into the big box inside the fender, which in turn leads to the airbox with the filter. Why not go straight from this intake to the filter? I suspect the big hidden box in the fender is an air/water separator for wet conditions - air and rainwater go into the firtst intake, but only the air is drawn back up to the filter box.

So the stock setup is a cold air intake, except the air is routed through a contraption worthy of Dr. Seuss.
 

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Interesting stuff. Learned something today. Thanks. I'd have never guessed what that extra tube was. I didn't even realize it was closed off on the end since, as I said, mine points down toward the ground and I never checked it for an opening. Just figured it pulled warm air from the engine into it anyway, without actually attaching to the exhaust.

Placement of the exhaust differs from any other vehicle I had before, so, it seemed plausible to reason Subaru had to skip the connection. Ha ha! Good to know they don't leave open pipes hanging in mid-air.

Still, a strange thing to me. Means I have plenty to learn about this car.

Hey, maybe people could build all sorts of tuned pipes for several frequencies and the car might play musical notes as the RPM's change! ;) Again, I'd never have guessed this. I thought the only sound-sensitive region was at the exhaust side, even though I used to run a 4 barrel carb without filter "plenum" to listen to the suction noise it made when revved up. Knew the plenum thing for non-fuel injected engines, not that it might be the same word for these boxed filter kind. Obviously my knowledge is limited to whatever I've owned before-- and always not complete.
 

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The_Lizard said:
So the stock setup is a cold air intake, except the air is routed through a contraption worthy of Dr. Seuss.
Well that's kinda what I was getting at, the '97 (all 1st Generations?) Outbacks already have stock CAI setup...so even if I made one myself, it would do essentially the same thing as what the stock setup does, perhaps less effectivity.
I guess I just don't understand why they made it different in the 2nd Gen. and onward.

And all the discussion about the snorkus is focused on newer scooby setups so I'm not really sure where it is located in my setup, at the very least I'd like to take that part out so I get some fat sounds out of my old baby.
Your links seem to suggest that the purpose of that phallus is solely to supress intake noise, so techincally, if I removed it and covered it's hole, I would hear more intake noise...
But Brian says that it is used to store extra air for torque, so technically, if I removed it I would lose torque/power...

Someone give me a definitive answer!
 

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FMGreen said:


if I removed it and covered it's hole, I would hear more intake noise...
You probably would, or maybe only at certain RPM ranges. But it would still be muffled somewhat by going through the air filter.

Personally, I wouldn't mind a little more intake noise, gives the pedestrians a little more warning when the light turns green *G*
:cool:

You're a musician, you deal in sound, you should play around with the possibilities. Put a microphone in the intake, feed that signal into the radio and out through the subwoofer....



:p

(edited to add) the heated-air connection between the intake and exhaust is called a manifold stove or choke stove.
 

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Lol...just read this thread... The first question that came to mind when I popped the hood for the first time..."what the **** is that snorkel looking thing??...". At first, I though it might be some type of bypass valve. However, it's installed after the MAF. Now I know! I too would really like to see some pics of the homemade cai.
 

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One other thing - that business about air storage ... *drums fingers* well if it isn't pressurized, and it's only at ambient air pressure, then what's the difference between that air and the air in the rest of the intake?
 
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