Optimization of crankcase ventilation (KGE) - oil separator, oil catch tank, oil storage tank - OIdtimerparts

27 Mar 2022

Optimization of crankcase ventilation (KGE) – oil separator, oil catch tank, oil storage tank

How does the crankcase ventilation work and what is it needed for?

In internal combustion engines, there is a crankcase ventilation in order to be able to set the correct pressure ratios. This crankcase ventilation also ensures that the leakage gases generated in the engine are discharged. These oil gases are discharged from the crankcase via a valve.
But what happens to the discharged oil gas? Due to the oil content of the gas, it is not environmentally friendly to discharge it to the outside. The oil would be released into the environment through condensation. This is not TÜV-compliant and is also harmful to the environment. For this reason, closed systems of crankcase ventilation are set up in which the resulting oil vapors are fed into the intake air of the engine. It is added to the fuel-air mixture and fed into the engine.
There are different systems, depending on the manufacturer and model, in which the excess pressure in the crankcase causes the valve diaphragm to open and allow the oil vapor to escape. If the pressure is now lower again, the valve remains closed until sufficient pressure has built up again in the crankcase.

What is the disadvantage of a stock crankcase ventilation?

The problem with the venting system described above is that the oil vapors generated in the KGE are fed unfiltered into engine intake air. This feed can cause the throttle valve to become oily and the engine’s fuel-air mixture to deteriorate. Although the engine burns the oil in the combustion process, the fuel quality is reduced and the performance decreases.
This is particularly the case with performance-enhanced engines such as turbocharged engines, which are optimized for good fuel quality. It has a particularly negative effect on engines that have been tuned for fuel with 98 or 102 octane in order to optimize performance. If the unfiltered oil vapor from the crankcase ventilation is now fed to the engine via the intake air, the quality of the gasoline-air mixture drops and the engine starts to knock. In newer engines, there is a knock control system that compensates for this. In any case, this can result in a loss of power and, in the worst case, damage to the engine’s valve train.

How to optimize the crankcase ventilation?

A good optimization option is the use of an oil separator or an oil catch tank. These tanks are installed in series in the crankcase ventilation circuit. Ideally between the valve of the breather and the intake air supply, e.g. in front of the intake manifold.

Oil tank in detail

In this oil tank, the oil is filtered and stored, so it is stored in the tank and can later be drained in a controlled manner when the tank is full. There are various operating principles and systems that can be used here. In the example photo below, the oil separator was connected via silicone hoses and positioned easily accessible in the engine compartment to be able to drain the collected oil at maximum level.

We hope the explanations will help you to optimize your engines as well! If you have any questions about this topic, please send us an email!

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