Oil Catch Can

[Richard]

If you are fitting a non vented catch can to an engine, what is the best way to hook it up?
A: In the line between the cam cover and the intake pipe
B: In the line between the cam cover (PCV) and the intake manifold
C: connect to both the cam cover outlets only.

 

[bazeng]

If you connect to both cam cover outlets you are basically sealing the rocker cover. This option will not work.

You can do either A or B but I would remove the PCV completely and screw in a barb or weld a fitting. Then connect both ports to the catch can and then vent it back into your intake pipe or atmo.

 

[EVO-00X]

^^ yeah thats what I've done. I had 2 x -8AN fittings welded into the rocker cover going to the catch can. Then from the top of the catchcan I've had to get a hose going to the turbo intake pipe (see attached pic). This is the only way the engineer and RTA would have passed the car for emissions. A breather on top of the catch can is illegal and a defect and can attract an EPA fine.

Option C wont work as you must have the catch can venting somewhere otherwise your crankcase pressure has nowhere to go and you'll start popping your dipstick and get oil leaks in your engine from leaking gaksets.

 

[Richard]

I hooked it up like this. (option A)
I figured that it was better here as this way all the oil that would go into the intake, turbo, intercooler, piping and also gum up the throttle body and intake plenum is caught here, the PCV valve will only put a little straight into the intake plenum which isnt as bad as the other pipe.
Please note this is a stock set up , no welding fittings etc.

 

[SIVART]

thats how your ment to do it Richard, the PVC valve way is better when you have a aftermaket ECU

 

[ENGINR]

I'm doing mine the same way as yours Richard - maintaining the standard PCV valve to intake manifold connection.

 

[milkandoj]

Im jumping on this jolly ol bandwagon to :w00t:

 

[EVO-00X]

I did mine the way I did because I had to get the car past emission tests. Believe me, Im dreading the idea of oil lining the inside of my turbo, icoola and piping (I've only driven approx 300km in the car at the moment). Now that its registered and on the road I can look at alternative 'cleaner' methods... but cleaner for the engine has its drawbacks.

I was thinking about running the black hose into the airbox, and inside the side wall of the airbox would be a breather (hidden under the cover). But most of the time I've seen breather setups they stink of oil unfortunately and you cant hide the smell. Having it close to the pod filter would also increase choking it up. The breather method is the best method for your motor but unfortunately isnt the best method for the environment. If you can live with the smell and maintenance of a breather setup either on top of the catch can or elsewhere, it will keep the oil out of your intake piping for good (This is the way Buschur and many others have been doing it for years).

Looking back at the stock PCV method it also has its problems. If youve ever removed one from the rocker cover and taken a good look at it you''ll find it has a very small diameter pipe and unfortunately the parts inside it can choke up in either the open or closed position. When they close up you're bound to get oil leaks from unrelieved pressure, something none of us want. When its functioning properly quite a lot of oil gets sucked directly into the intake manifold and plays with the mixtures. If it were to go through a baffled catch can first at least it will have a chance to lose some of the oil vapours inside the can before making its way to the intake manifold.

Perhaps running a larger diameter check valve (like a large diameter aftermarket one-way brake valve) that opens up at a certain vacuum level would remedy the factory pcv choking problem. So basically opening up the PCV valve hole for a larger fitting and hose, run a hose to a large diameter check valve to a catch can, and then back to the intake manifold. The other outlet on the rocker cover can also go through a baffled catch can before going into the intake tract.

Its damned if you do and damned if you dont pretty much lol...

 

[milkandoj]

You've got some good points.
For my car i was going to run strait breathers from both ports, but ive been reading and have been swayed to only enlarge the breather on the side without the pcv. And keep the stock pcv setup. As its more for sucking away the water condensation.
I do see what you mean about the small size of the pcv valve.
But if your keeping the stock valve its only sucking up moisture and oil at vacume at cruise. At boost its closed anyway so doesnt need to be massive.
Do you think what it would be letting into the intake manifold under vacume at cruise would cause problems?
Its not under throttle when the oil gasses form the other port can hurt the fuels octane.

But enlarging the open breather on the side of the cover it can vent blowby ect under boost better.

I figure i havent had problems with oil leaks of dipsticks popping out but have had a bit of oil in the intake, but wasnt making much power before. See how it goes with a little more boost.

If the pcv was kept fitting a larger one could be a good idea though