I just started writing the article about an hour or two ago, and am still actually learning myself but wanted to see what everyone else thought of the article. Pictures will accompany the article but for now just words will have to do. Any and all feedback, suggestions, and comments is/are welcome.
In an engine, there are two areas of air pockets in which the air is not directly related to combustion. Within these two areas, oil and air are separated from the combustion chambers and coolant jackets for the purpose of lubrication of the engine. The upper air and oil pocket is constrained by the valve cover at the top, and the valve seals at the lower end. The bottom air and oil pocket is constrained by the piston rings at the top and the oil pan in the bottom.
In a perfect world, these two lubrication areas would not pressurize. However, in real life compression leaks by valve seats and piston rings in what is called blow-by. Blow by introduces pressure into the two pockets of air and oil (the head and the crankcase). In addition, heat caused as a byproduct of combustion causes air molecules to expand which also causes the pressure to increase in these lubrication areas. If no ventilation system was employed to release this pressure, it would find the point of least resistance to escape, which could be oil seals…or worse.
To relieve this pressure, a system called Positive Crankcase Ventilation (PCV for short) is used. It is a closed system that takes the pressurized air and oil vapor from these two lubrication areas and introduces it back into the combustion chamber, by way of vacuum caused by the intake charge.
On the bottom end, most VTEC engines use a breather chamber located at the back of the block, underneath the intake manifold. The purpose of this breather chamber is to separate air from oil. The oil is returned to the crankcase while air is sucked into the intake charge. A valve called the Positive Crankcase Ventilation (PCV) valve controls the flow of this breather chamber valve to the intake manifold. The PCV valve is spring loaded and detects variations in pressure between the crankcase and intake manifold and opens or closes accordingly.
On the top end, the valve cover has a thirty degree fitting and the intake has an opposing thirty degree fitting, both of which are attached by a hose. As the intake charge creates a vacuum, oil vapors from within the valve cover are sucked into the intake stream for combustion again. This reuse of oil vapors is good for vehicle emmisions and consequently, the environment.
However, the factory system does not do an efficient job of filtering out oil from air. Oil mixed with higher octane gasoline will effectively lower the octane rating of the mixture. In simplified terms, octane is used to rate the resistance to knock of a substance. In high compression or high boost applications, this can be fatal to an engine. The detonation caused by lower octane combustion will eventually destroy and engine if not monitored and appropriately adjusted for. By the same token, removing this oil from the combustion process allows higher compression and higher boost applications to be run more reliably. What can be done to make the Honda breather chamber system more effective?
A catch can is a cylinderical device with an inlet fitting, outlet fitting, and internal baffeling which further filters out oil from air. Nicer catch cans can come with internal baffeling already in place; an external viewing glass to check the oil level; and sometimes with a drain valve which allows the user to drain oil from the catch can without having to remove it. If baffeling is not included with a kit, steel wool has been used in the past.
A typical Honda catch can set-up is added in addition to the existing breather cahmber system. The catch can inlet attaches to the PCV valve by a hose. The oil and air vapor is drawn into the catch can and the relatively clean air releases back into the intake charge via a fitting on the intake manifold. Reinforced clear hoses are typically used to connect the whole system. These hoses are used because the vacuum has been known to collapse hoses and because the clear hose is convenient to see that the system is working properly.
