7AFE Catch Can setup - confused by oem breathers Options

[atlex]

This isn't a celica I've got, it's a Toyota Sprinter Carib - a 4WD estate based on the corolla chassis, but with either a 4AFE, 7AFE or 4AGE (20V Black Top) engine.

Mine's the 7AFE .. Z Touring, 4WD, AE115 model.

I'm asking here because this is one of the better forums for 7AFE engine knowledge

Photo here: https://trull.org/alex/media/pics/car/carib...ue/on_farts.jpg (sprint (f)hart wheels)

Anyway, I see two breather hoses, and this has confused me a bit. One hose, the left-hand one, has the pcv valve, the other hose, which just goes to another hole in the intake plenum, has no pcv valve. I'm trying to understand why they've got two hoses to from the cam cover to the intake plenum, one of which has a check valve, as this doesn't make sense to me.

Typically if you have two paths between two chambers, and one has a check valve in it, and there is some pressure difference causing flow, the flow will favour the path with least resistance - it looks to me like the pcv valve shouldn't see flow ?

Normally the second breather hose would be run pre throttle body to provide some through-flow under vacuum... and the pcv valve would be in constant use as it would be the only path between the source of vacuum, the intake plenum, and the cam cover..



not my engine but very similar.

I'm thinking to block off the right hand hose on the plenum side, put a breather filter on the cam cover side and then run the catch can between the left hand ports - pcv valve, catch tank, intake plenum..

[Smaay]

you are pretty much correct. the PCV has a check valve so it only lets vacuum air from the intake manifold through it. The intake manifold sucks air through the PCV into the intake. the other breather hose is crankcase ventilation. its the source of air and typically after MAF before throttle body. since this car has not MAF its between the filter and TB.

the best place for a catch can is in between the PCV and intake manifold.

now why do you think you need one? typically the 7A doesnt need one

This post has been edited by Smaay: Oct 28, 2018 - 11:06 PM

[atlex]

Thanks for clearing that up ^

As for why a catch can ? on this car ? Force of habit on all older cars in my stable - It's a high mileage engine, new to me, and where I'm probably taking the car (east of eastern europe.. ....) the fuel may not even be that good - sub 95 RON - worse than 91 PUMP in amerikanski. Anything I can do to clean up the intake charge - I also like to know what's coming out the breather so I know the condition of the thing. I know it's overkill, but overkill is my style.