MAN Truck & Bus
MAN Truck & Bus
An engine operated with inverse energy flow, i.e. drive axle – transmission – engine, uses its drag torque to act as a brake. Improvement in braking performance is achieved by reducing exhaust gas flow during the discharge cycle or limiting the expansion effort by targeted decompression. All engine braking systems are primary braking systems, so they depend on engine speed (higher speed results in greater braking performance).
Conventional exhaust cut-out engine brakes are inadequate to meet the high requirements of increasingly powerful diesel engines. The standard engine brake with exhaust cut-out only uses the engine's braking energy in the gas exchange loop. The actual compression is lossless, which means that engine brake energy cannot be used during the compression and expansion cycle despite actuating the engine brake (compression and expansion continue unhindered). Commercial vehicle manufacturers have developed different methods for releasing engine brake energy even during the compression and relaxation cycle. .
A typical method for enhancing braking performance in combination with an exhaust cut-out brake is the MAN EVB (exhaust valve brake). It is also referred to as the cantilever brake due to its mode of action. The MAN EVB engine brake was presented at IAA 1996. It offers greater efficiency compared to the other methods, and with lower construction expenditure.
The MAN EVB was once again improved for engines in the D3876 series compared to the EVB in the D2066 and D2676 series. High braking performance is already available in the medium speed range using the D3876. The optimised EVB in a D3876 has a maximum braking performance of 340 kW at a speed of 2.400 min1-.