Oil Catch Tank and Tuning

An oil catch tank is an external oil catch can into which the oil vapours from the crankcase are directed. It is therefore a part of the crankcase ventilation. These vapours consist of an air–oil mixture, which is separated again in the catch tank. The oil is thus separated from the air and remains in the catch tank. The air cleaned of oil is either released directly into the atmosphere through a filter (open system), or returned to the intake tract for combustion (closed system).

The oil catch can prevents oil from freely entering the intake and sticking everywhere. Over time, oil sludge and carbon form, coking the valves, narrowing passages and clogging the throttle body. This, in turn, leads to a number of problems, including significantly reduced power and poor throttle response, up to a premature engine failure. And that is exactly why an oil catch tank is so important, especially in performance-enhanced vehicles.

Regardless of construction method and type, every internal combustion engine generates crankcase pressure. The hot oil constantly releases oil vapours, caused by the various motions within the engine: the crankshaft rotates and dips through the oil, the oil pump moves the oil around and foams it, and when driving it sloshes around. The resulting pressure must be relieved, as, in the worst case, the oil would be displaced from the sump and the oil pump would only be able to suck in air. Seals and other components would also be damaged, quickly leading to a catastrophic engine failure.

The crankcase ventilation in series prevents it from happening in a more or less elegant manner. Here, the venting usually occurs via hoses and lines to the cylinder head cover and engine block. In some vehicles, a PCV valve is also used. The oil vapours are conveyed back to the intake tract in all cases unfiltered and fed to the combustion. This leads to the aforementioned complications: oil sludge forms, clogs everything up, and causes various problems that can even lead to engine damage. The more power a motor has, the more susceptible it is. Turbocharged engines are also more often affected than naturally aspirated engines.

Another important function of the catch can is the cooling of the air before it returns to the intake tract. And it is precisely here that the quality of different catch cans varies enormously. The longer the air remains in the catch can, the cooler it becomes and the better it is for the intake. At the same time, the air inside the container must not become stagnant.

Low-quality variants are often made from equally inferior materials and are poorly manufactured overall. In the worst case, they allow oil vapours to escape, which can ignite in the engine bay and cause an engine fire.

High-quality catch tanks are designed to ensure air is routed efficiently through the container to maximise the surface area for cooling while still allowing air to escape evenly. Therefore, the size and material of the component are also relevant – the larger the tank, the more surface area is available for cooling. The connections must be optimally finished as well to seal the system and ensure smooth venting.

Even the ongoing maintenance is a relevant factor when judging the quality of a catch can. Inexpensive variants often have to be completely removed in order to be emptied. High-quality catch cans for example, feature a drain plug in the base to allow the collected oil to be returned to the oil pan. To make maintenance even easier, the best catch tanks also include a Dipstick, which facilitates reading the oil level.

Do you have questions about the catch tank? Feel free to message us in the chat. We are always happy to help.