During the past few years, economy of commercial vehicles has increased considerably due to higher engine outputs a+ lower engine speeds together with enhanced fuel economy.
However, the average speed of commercial vehicles is not only determined by the speed attainable on level ground and on uphill gradients, but also to a large extent by the speed attainable on downhill gradients, with the latter depending on the available constant braking power. Since the displacement of commercial vehicle engines has not been increased or has even become smaller, their braking power has increased only slightly ot not at all.
In order to enhance the overall economy of commercial vehicles, it was therefore necessary to increase the engine braking performance as well since the wheel brakes cannot be used for constant braking and additional systems for continuous operation are very complex.
The function and setup of known engine brake systems as well as their limits ar outlined in a basic presentation.
The function and setup of the new Mercedes-Benz engine brake with continuously open decompression valve which has been introduced into standard production will be described, and the engine braking performance it achieves is shown in comparison to the conventional engine brake with exhaust throttle.
The speeds attainable with the new Mercedes-Benz engine brake with continuously open decompression valve on downhill gradients are compared with the previously possible downhill speeds on one hand and with the speeds attainable by means of additional retarders on the other hand.
Also, variants are described which will even further increase the braking power attainable with the engine brake with continuously open decompression valve, e.g. modified exhaust gas routing.