Fiesta ST - Oil Catch Cans

The long-awaited debate; Oil catch cans. Are they needed? Which side of the PCV system should I place the can?

Oil catch cans are designed to trap oil vapors that may be ingested into the engine through the PCV system. These vapors can cause carbon buildup on the back on the intake valves (which is notorious in direct injection engines) and may also cause unwanted misfires/detonation under WOT conditions. 

If we break the PCV system down into two sections; vacuum and boost. The “vacuum” side would be the hose that connects the intake manifold to the valve cover, as the intake manifold is drawing air from of the valve cover via engine vacuum. The other side that connects to the intake/crossover pipe is our “boost” side. This side vents when there is positive pressure in the crankcase and is released into the intake (as a sealed system).

The catch can that I typically recommend to my customers is the Damond Motorsports catch can with VTA option. This kit is mounted on the “vacuum” side and utilizes a breather filter on top with a one-way check valve to vent under positive crankcase pressure. This setup is going to be most beneficial for vehicles that are driven frequently and are in vacuum for the majority of their running life. Below is a picture of the kit installed, and also the internal baffles that are used during the production of the can. (Thank you Matt, for sharing this photo with us!)

As discussed in my previous article, there is an oil drain-back system from the factory on the “boost” side of the system. It is located under the valve cover and drains the oil back internally. So I do not see it as necessary to have a can on that side of the system. The exception of course might be for a high boost build that is looking to evacuate all pressures from the crankcase ASAP, and emissions may not be as important. In this case, another can could be used and would likely be vented to the atmosphere (race applications).

Link to Damond Motorsports Oil Catch Can for Fiesta ST:

Ford Fiesta ST Oil Catch Can kit | Damond Motorsports