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.
Last edited by Kiffbliksem; 04-03-2017 at 11:34 AM..
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.
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...
Last edited by Vancouver98STi; 05-29-2017 at 03:32 PM..
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.
2001 SRP Coupe 8300RPM SOHC 257, 71 HTA, DCCD RA Drivetrain and ms3-Pro
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!
Last edited by Vancouver98STi; 01-30-2018 at 03:04 PM..