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Or the alternate title "Oh Christ! Gavin is messing with engines now. Run for the hills."

One of the first things I did with the car was I cleaned the intercooler. I had read on this site that others had found quite a bit of oil there. This oil would coat the inside of the intercooler creating an insulating barrier and making the heat exchange(from air to metal to air) inefficient. Cleaning mine I found just a light/medium covering of oily residue inside the intercooler.

I took this to be a good sign that the engine was healthy. But where did the oil come from?

(Bear with me with my feeble attempts at engine theory.)

What I learned was that this was the direct result of the workings of the PCV (Positive Crankcase Ventilation) system. Oil vapor and other pollutants are created by the hot oils in the crankcase. Once upon a time, these vapors were vented into the atmosphere contributing to much pollution. Nowadays this is eliminated via the PCV system whereby, using engine vacuum, these vapors are extracted from the crankcase and routed back into the intake tract to be eliminated(or nearly eliminated) in the combustion chambers.

This is all good for the atmosphere and I think this is a nifty trick to solve this problem. However, being a performance minded person, there were two glaring issues I could see with this system.

One: oil vapor is only oil vapor when hot. When it starts to cool it will congeal and deposit itself as oil droplets (reduced intercooler efficiency?)

Two: Air/fuel/spark. This is the classic trio used in tuning an engine. Nowhere does it say (a mixture of oil vapor and )air/fuel/spark. All things considered this oil vapor reduces the amount of available air that the engine recieves. Sounds like lower performance to me, but what do I know? Im a suspension guy.

This all gets worse when the engine is racing at high RPMs. Not only is there oil vapor to deal with, but oil gets sloshed around in the head and will sometimes try to make it out of the hoses for the PCV system. I would be autocrossing quite a bit with the car and really wasnt looking forward to the maintainance required. I needed a way to prevent this from happening.
An oil catch can seemed to be the solution for the issues at hand.

For the time being however I added this little item to the line going from the Intake manifold to the intake tract.



Its a simple fuel filter that acts as a "crap trap". It worked very well...perhaps too well, as its paper element would get saturated with oil and eventually become clogged. With an escape being blocked the head would get pressurized and try to relieve the pressure by going through the valve cover seals. I needed a more permanent solution.

There are quite a few resources out there for catch cans from DIY to premade items from Greddy, Cusco, JAZ etc. They are usually internally baffled or have an element to separate the oil from the air. Some of these catch cans are just that, "catch cans", and vent to the atmosphere (ungood). They are also about 1 liter or so, somewhat expensive and are made to be very er...noticable.

I wanted something simple, straightforward and effective. While searching I came accross DIY examples using compressor air line filters. They separate water vapor in compressor lines so the internals dont rust.



23$, 6" long with an internal baffle and filter, a clear container with which to visually check accumilation, o-ring sealed(and rated to some ridiculous PSI) and a petcock to drain fluid. A couple 3/8" treaded barbs and a bit of hose and I was ready to go.......Almost.

As much as I read, something was escaping me. Most installations had only one catch can installed. Usually they are inline with the PCV valve and the intake manifold. This made sense as the engine is creating vacuum from the IM drawing oil vapor out through the PCV valve and into the manifold. BUT..I (and others)was experiencing oil/oil vapor entering the intake tract from the IM and seeing the results of that in the intercooler.

It seemed that there was a need for TWO catch cans. But how could this be as all of the previous installs I had seen had only one? I started to think that I was incorrect, others were only installing one catch can, so clearly the catch can should be installed on only one line(PCV>IM or IM>intake tract)......but which one? For a long while I could not reconsile this dillemma.

It was only until I stumbled accross an installation on Scoobymods that I realized My original thoughts were correct.

http://www.scoobymods.com/forums/showthread.php?t=3346

There are TWO paths to ventilate the crankcase vapors. One, as mentioned, through IM vacuum from the PCV valve. The other is through the intake tract coming from the valve cover. Under boost, you have positive manifold pressure instead of vacuum. To prevent the valve cover from being pressurized by boost, the PCV valve closes. If it were not for that, boost pressure would blow the valve cover seals and send oil leaking everywhere(PS: if this is happening to you, check the PCV valve for failure). Oil vapor still has to be evacuated, and that leaves the vaccum in the intake tract created by the turbocharger.

Why it is that there have only been single catch can installations on the "net" I have no idea, but it was clear to me that there was a need for two (at least in this application and maybe others)

PCV side.






Intake tract side





Well there you have it. Dual oil catch cans.

I have had a chance to test them out on a 250 mile round trip and an autocross. For better or worse they work as intended and I have noticed a small amount of oil collected in both.(breathe free little engine, breathe free)

Comments critiques, all welcome [Comments can be found here: http://www.mx6.com/forums/showthread.php?t=109948]

Gavin
 

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Discussion Starter #3
500miles down the road.

PCV side




Intake side



Doing ther jobs as intended.

(this reminds me, Ill have to empty the intercooler one of these days)

Gavin
 

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Simply awesome - I love ur practical approach to solving this prob - karma.

The only qn in my mind is... would the collectors restrict the airflow 'too much'?
 
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