Bad for environment and engine performance

Crankcase gas originates from leakages that occur between the piston rings and the cylinder walls of an engine. The gas leaks down into the crankcase, where it generates a fine mist of oil droplets from the oil used for lubricating and cooling the engine.

In order to prevent the pressure in the crankcase constantly increasing, the crankcase gas needs to be vented off. The most common solution to this problem has been what is essentially a simple hole in the crankcase.

The gas is then led through a pipe below the engine and out. A truck engine with 500 brake horse power creates around 10 cubic meters of blow-by gas per hour, containing 5-10 grams of oil. In a year this corresponds to around 30.000 m3 of blow-by gas.

Even more important in the future

Because this inevitably means greater oil consumption, it is not the best solution for either the environment or the engine performance. Oil traps are therefore commonly used to prevent the emission of too much lubrication oil. Nevertheless, this still results in an annual loss of as much as 25 litres of oil from a typical truck engine.

To avoid the oil wastage, some engine manufacturers have led the gas back into the engine’s air intake. This solution causes other problems. The blow-by gas contains oil and grime particles that can deposit on different components in the engine, thereby reducing the efficiency.

Coke and oil particles can also deposit on the turbo and reduce its performance. In the future trucks will be fitted with catalytic converters. Then it will be even more important that the blow-by gas is clean before it is led back to the air intake.