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98 2.5RS, GT30R, Haltech E1000
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Discussion Starter #1
I have teed off all my vent hoses into a single small brass fitting in my intake. I'm assuming this is probably not enough airflow for everything....

What do you guys vacuum lines and IAC, PCV, valvecover vents look like? Please post me some pics!!!
 

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01, RS Sedan STM
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61 Posts
Ignore the fact that's the manifold is different because it's still an ej251. The principals can be applied to the stock manifold.

1. Air assist is still electrically connected but the air lines are removed and plugged.
2. Red: remote IACV, feed line for air assist is capped off (1/8NPT AN male fitting #4, with cap)
3. Orange: 3 arrows point to crank case vent lines, catch can is circled in orange, literally a collecting can where all breathers dump, mounted low in the engine bay. It's easy to clean, never have pressure in the lines, no smells inside the car, and not rerouted back to intake.
4. Yellow: Map Sensor
5. Green arrow: I now use the stock map sensor
6. Blue: cruise control line. This is also where I tap for my boost/vacuum gauge.
7. Purple: IACV block off plate, also below the throttle body is an unused vacuum port to use with a BOV.
8. ------: you can see the brake booster vacuum line.



Don't share your FPR with any other lines.
Don't share your MAP signal with any other lines.
 

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98RS +06STi
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41 Posts
ideally you want your valve cover vents and PCV running back into your turbo inlet for vacuum source. this helps pull pressure out of where it should not be. I ran my valve covers through the stock line along the intercooler, T'd them, ran to a AOS (homemade). PCV runs right into it's own AOS. these two AOS come right together at a T then dump into the intake. ideally the PCV and valve covers would go into different spots on the turbo inlet, but mine doesn't have any bungs.
 

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1998 JDM Impreza STi v4 GF8
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46 Posts
ideally you want your valve cover vents and PCV running back into your turbo inlet for vacuum source. this helps pull pressure out of where it should not be.
I'm a little confused by this comment. Maybe there's a difference with how various Subie engine have their PCV systems set up.

I'm just about finished the custom oil catch-can(x2)/breather system on the EJ20K engine in my '98 JDM Impreza STi wagon. I've basically retained the original routing, and it's the vacuum from the intake manifold (through the PCV valve) which pulls gases/pressure out of the crankcase. Fresh air is supplied to the crankcase from the pre-turbo intake through the breathers in the valve covers. Now granted, that's during non-boosted operation. Under boost (when the PCV valve closes)... yes, crankcase gases are being pushed/drawn into the pre-turbo intake.

Perhaps these diagrams that I was using in a different discussion might be helpful...



 

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2001 SRP 2.5RS/RA/SOHC Monster
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This is my set-up. One catch can for the crankcase vent to the PCV valve and another for the Valve cover breathers to the turbo inlet.
 

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1998 JDM Impreza STi v4 GF8
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This is my set-up. One catch can for the crankcase vent to the PCV valve...
How does your system handle boost conditions when the PCV valve is closed? Does the crankcase vent no longer have a path back to the pre-turbo intake through the factory restrictor fitting?
 

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2001 SRP 2.5RS/RA/SOHC Monster
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Hardly anything factory about my set-up. During boost conditions if there is any excess crankcase pressure it will vent though the valve cover to the second catch can and be fed to the turbo inlet. Soon as the manifold sees vacuum again it will scavenge the gasses from the crankcase. I did propose a check valve on catch catch to PCV line that went to the turbo inlet however this was generally considered a bad idea by those that I consulted. Since this would most likely cause any crankcase gasses to bypass the PCV and be fed directly into the intake tract.
 

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1998 JDM Impreza STi v4 GF8
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During boost conditions if there is any excess crankcase pressure it will vent though the valve cover to the second catch can and be fed to the turbo inlet.
My two catch-can hose routing/setup is almost exactly the same as yours, except I didn't feel comfortable eliminating the factory restricted passage back to the pre-turbo intake. So I used the original fitting and just plumbed it in after the catch-can in that part of the system. This way when the PCV valve is closed while the engine in under boost, the crankcase can still vent through its own port as well as through the breathers in the valve covers. That's the theory anyway. :)



Crankcase gases continually go in one direction through the top catch-can pictured above. During boost, these gases go into the pre-turbo intake (because the PCV valve is closed). When not under boost, the gases are instead sucked through the open PCV valve into the aft-turbo intake.

It's interesting to note that gases actually go in two directions through the lower catch-can (which makes in/out orientation of the can important). While under boost, contaminated crankcase gases travel from the valve covers, through the catch-can and into the pre-turbo intake. Those gases need to be filtered. When not under boost, clean air is being drawn by crankcase vacuum from the pre-turbo intake, "backwards" through the catch-can, and then through the valve cover breathers eventually into the crankcase.

It's no wonder there's so much confusion about this process on the 'net!
 

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1998 JDM Impreza STi v4 GF8
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I'm just about finished the custom oil catch-can(x2)/breather system on the EJ20K engine in my '98 JDM Impreza STi wagon...
It's now installed and functional. Engine bay isn't exactly pretty (damn that flaky red paint that Subaru put on all STi engine intake manifolds), but it seems to run just fine.

 

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01, RS Sedan STM
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61 Posts
Kiff,

what are your thoughts on your intake set up?
What connector did you use?
Any actual changes?
Did you tune?
1) Loud! :noes: I don't love the loud intake.
Also it gets wet! I am running a different set up now.
But honestly very efficient way to get cold air, it perfectly sits in the hood vent.
I don't think it will line up for RS manifolds the same way...
2) It's just a 45 degree elbow of appropriate sizes go around the outside of the intake box hose, and then obviously around the outside of the throttle body.
3) The higher RPMs are much happier with that set up. Rev matching is a bit easier, and noticeable more power in that area of the rev range.
4) Yup tuned. I have to tune in any changes with the WRX blue injectors otherwise things skive too rich or lean quickly.
 

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1998 JDM Impreza STi v4 GF8
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46 Posts
You relocate to trunk or in fender?
My "solution" was to just eliminate it. Period. Truth be told, I've rarely ever used the windshield washer in any car in the 45 years (gulp) that I've been driving.

As you well know, the engine bay is very cramped in an Impreza. For me to find a spot for two oil catch-cans, something was going to have to exit the engine bay. The other option I briefly considered, was to relocate the battery to the back of the car. Removing the windshield washer reservoir was a whole lot easier. :)

I'm curious... how is it you have a spot there to mount a reservoir? Where's your ABS pump module?
 

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2001 SRP 2.5RS/RA/SOHC Monster
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No way I could eliminate it where I live. So much salt and sand gets used in the winter that your windshield will become opaque in no time flat.

ABS has been deleted.
 

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1998 JDM Impreza STi v4 GF8
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No way I could eliminate it where I live. So much salt and sand gets used in the winter that your windshield will become opaque in no time flat.
Ah... I was wondering why other people had so much trouble with bug spatter! Now I understand.

ABS has been deleted.
I'm aware that this is done by people (although I don't know why)... but as someone who has never owned a car with ABS previously, I'm looking quite forward to using ABS brakes at autocross this summer. Maybe I'll be flat-spotting my track tires a little less now. :lol:
 
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