Originally Posted by hobbs

If you think this is bad head over to the dash where you have a ton of people with inflated egos that act like this.

But now I know why hes offering people 60 dollars shipped on SR CASs, guess those entry level chem classes are expensive.

Originally Posted by RalliartRsX

I have a feeling King is writing out a lengthy /part 3 or /part 4 for me !

Originally Posted by RalliartRsX

Thanks for taking it easy on me. I was a bit brash there, I will admit

Originally Posted by Kingtal0n

Ill play your game because these are great points that have been left out of this discussion because it is beyond the scope- but you seem curious so Ill do my best to help you.

What is pushed out of the PCV,
This is the same as question #2: Composition of what is removed from the crank case. And what collects in the can? this is also a composition question. You asked the same question 3 times.

but thats ok. It seems like you are entirely interested in what the engine is producing and what is getting into the engine oil and vaporizing. Which is awesome!


The Composition of engine oil is where we shall begin. Does anybody know what is inside engine oil? Oh wait, every engine oil is different. All different manufacturers of engine oils use different blends of additives in their oils. Therefore, it is impossible for any individual to know the composition of their engine oil unless they themselves created it.

We can make generalizations anyways:

The main ingredient of engine oil is long chains of carbon, fully hydrogenated. There are many volatile components in engine oil as well, but I will get to that.


So when you first pour engine oil into a fresh brand new engine, you mostly have these long chains of carbon, "alkanes". They sit in the pan right?

So you start the engine now. Combustion takes place, and some of that leaks into the engine oil (blow-by). Now your engine oil is becoming contaminated with byproducts of combustion. Those byproducts include gasoline (shorter chains of carbon) and literally an almost infinite number of partially oxidized portions of carbon chains, both of oil and gasoline.

Let me repeat that another way. When you burn gasoline, you get H2O and CO2 IDEALLY. However, due to the additives, and the stoichiometry of the process, and the temperature at which it occurs, and other factors, you also wind up with thousands of by-products, some of which are toxic, some of which are contaminants that persist in the engine oil, some of which harmlessly evaporate, some of which go on to perform further reactions to become something else. So in answer to the composition question, there are literally thousands, perhaps millions of possible orientations of molecules being produced, both entering and exiting the engine oil while an engine is running.


Lets classify some of them:
1. solid particulate. Metal atoms flaking away from the combustion chamber or cylinder walls. Metal debris released from engine bearing occasionally. Compounds of carbon that are partially oxidized that do not solvate well in engine oil. Anything in the atmosphere that managed to get into your engine (pollen, dust, fungus spores, hair, compounds of carbon from previously living cells, etc...).

These things will become evenly distributed in your engine oil, and hopefully the oil filter can remove them. Most of them do not evaporate and so they will rarely find their way to your catch can, unless carried out with liquid oil. Your best defense here is an oil change.

2. gaseous volatile compounds. These will evaporate and usually stay gaseous. The pcv system will direct them to the combustion chamber and they will be released into the exhaust for the most part. Any gaseous state molecules that find themselves in the catch can would simply diffuse right back out, being a gas.

3. Liquids that are temporarily vaporized by the vigorous churning of the engine, such as oil vapors. These are gas state molecules that behave as gasses but will probably return to a liquid state shortly after entering the PCV system. This is the oil that coats the inside of your intake manifold, and coat the rubber intake tube of your compressor inlet, and possibly your compressor wheel and intercooler. This is the main reason to add a catch can, inline, between the valve cover, and turbocharger. It will help prevent an oily mess from accumulating in your expensive turbocharger. notice, however, that the same effect may be acheived by an appropriatly lengthy tube, instead of a catch can. By giving the oily vapour a chance to settle somewhere BEFORE the air reaches the turbocharger, will acheive the same effect as "catching" it in a catch can. having a catch can also present an opportunity to catch a large volume of oil should the engine suffer catastrophic failure.


So, summary,
-solids generally stay in the engine, hopefully stop in the oil filter, and get changed with the oil
-gases that stay gases get exhausted
-liquids (like oil) coat any plumbing between the crank case and vacuum source
-nobody knows all the exact composition of all engine oils, all manufacturers use different additives
-thousands, potentially millions of different compounds are formed as by-products of a running engine in the combustion process