An oil catch tank, or in other words oil separator is a device located in the engine breather system. It is used to separate vapours from the valve covers and crankcase of the engine. All modern vehicles "recycle" the vapours from the engine, which means that the venting is done by exhausting them back into the intake. The advantage is a reduction in engine compartment odour and pressure. This system also brings a number of disadvantages:
- oil build-up in the intake manifold and intake
- high vapour accumulation leads to misfiring (blue smoke from the exhaust)
- engine knock can occur
- in combination with EGR systems, significant deposits occur in the intake and on the engine valves
Advantages of installing the vapour ventilation system (OCT):
- minimises oil entry into the suction system
- reduces fouling of the engine intake and valves
- captures water accumulated when using ethanol fuels
- reduction of engine knock
- specialises the looks of the engine compartment
There are 3 types of OCT devices available:
Venting to the atmosphere is provided by separators equipped with a filter or an open section. The oil vapours enter the plant where the liquid part is collected by settling on the walls or in a filter strainer and subsequently flows into the lower part. The vapours escape from the upper part into the atmosphere.
Closed-circuit separators are simply connected to the existing ventilation system. The vapours passing through the system are trapped on the walls or filter sections of the OCT where the excess oil is condensed and remains trapped in the vessel, with the vapours continuing on to the engine intake. This type of OCT is the most common and widely used of the range and is also suitable for modern vehicles.
Combination separators are the ideal addition if you are unsure of which OCT to use whereby by installing or blanking the filter you can turn this product into an atmospheric or sealed oil catch tank.
A common method of venting the valve cover is to use a universal mini filter, which allows direct venting to the atmosphere. However, the disadvantage is frequent smoking from under the hood and contamination of the engine compartment with oily oil vapours.