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Old 08-26-2003, 01:32 AM   #1
Scooby Specialist
Member#: 17181
Join Date: Apr 2002
Chapter/Region: MAIC
Location: Clarksburg, Maryland
2015 Subaru WRX
Red / 2012 RR Evoque

Default Interesting Intake theory for 2000-2001 RS

Alright. Last year when i first bought my car i had the Rallispec Short Ram intake installed in my car. I noticed that the hoses did not connect to the intake but connected to this "catch can" or wutever that had a little tiny breather filter attatched. The car ran smooth as ever but i wasnt satisfied.

so i got the Injen Cold Air intake and sold the Rallispec. The hoses this time, connected to the Injen intake. The car ran smooth and even better than the Rallispec for 2 weeks. then i dropped off my car at a body shop. and when i got it back, the car was still smoothed but seemed not as good. rated by "butt dyno".

this is my theory. with the Rallispec intake, the little air box with the catch can filter was used to fool the 2.5rs ecu into thinking that the car wasn't getting enough air flow. causing the usually RICH running RS to run more lean... and this equals more HP?!?!

after the installation of the injen, where the hoses connects to the intake. the air readings directly from the high flow intake reads that the air flow to the car is higher than "normal" so the ecu thinks that the car is running too lean. knowing the ecu, it likes to adapt to this type of crap, so i guess two weeks is enough time for it to start running rich again after the ecu has adapted. making the car richer makes the HP drop?!?

any feedback would be nice from you guys.

i might try to get another air box and breather filter and feed the hoses throught there, and use something to plug the holes on the Injen intake to see how it feels. im sure my car isnt going to blow up. i think it might be an interesting project.
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Last edited by AzNStiImpreza; 08-26-2003 at 03:57 AM.
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Old 08-26-2003, 04:24 AM   #2
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2015 Subaru WRX
Red / 2012 RR Evoque


i think ive just realized that the catch can breather filter thing im talking about is just an oil collecter, and it probably wont help the car lean out at all. but after reading some things, a catch can seems like a good idea, preventing oil from getting into ur intake.
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Old 08-26-2003, 10:11 AM   #3
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catch cans are good. they don't really need a breather filter ideally. you want to make the can into an oil separator... it'd function like those grease screens over the grills at McDonalds. oil hits a barrier and falls into the can while the air continues to go into the intake.

yeah, you're still getting some oil vapor, but the breather type catch cans just don't do their job nearly as well.

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Old 08-26-2003, 04:50 PM   #4
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The hoses plumbed into the intake can have a vacuum effect on the crankcase, allowing better ventilation and tighter ring sealing for a little more efficiency.

It can, however, allow oily residue to get into the TB and intake manifold, which may hurt efficiency over time.

I still have ours running to a simple breather.....but I'm just stubborn. Maybe I'll put them back into the intake....or from a catchcan to the intake during dynotime to see if there's any improvement one way or the other.

Jay Storm
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