Please forgive my ignorance, but what is the purpose of a catch can?
The top of your engine develops pressure from the engine simply running. The air that creates that pressure is “dirty", ie oil, fuel, etc. We don't want to just vent that dirty air to the atmosphere for environmental reasons so it is routed to the intake side of the engine.
Some fuel injected engines are port injected, meaning the fuel nozzle sits behind the intake port and sprays fuel into the intake port and onto the back of the intake valve. Some engines are direct injection and the fuel nozzle sprays fuel directly into the cylinder.
Since that dirty air is being drawn into the cylinder through the intake port all that crud comes into contact with your intake valve. On the port injection engines the fuel cleans that crud off. Gasoline is a solvent (kerosine/diesel is a lubricant). On the direct injection that crud from the intake doesn’t get cleaned off and will gunk up your intake valves.
A catch can goes between the vent port and the intake port (it’s one little hose that connects the two ports). All the can is, is a vessel with filters and such to catch that dirty air, filter out the oil and allow cleaner air to the intake.
Our GEN2 3.5 ecoboost engines are BOTH port and direct injection. So while the catch can will catch the oil our engines are already cleaning it off the intake valves.
If you watch some of the videos on these catch cans for the Raptor you will see a small amount of oil being collected over 3-4K miles. Considering the relatively small amount being collected and the fact we have poet injection, IMO the catch can is a bit redundant.
Note: The ‘19 is both port and direct injected I assume the 17 and 18 are as well. Also I did simplify my explanation for the sake of simplicity.
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