Bonanza effect

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The bonanza effect is a rocking of the engine block in certain series of diesel cars from the Mercedes-Benz brand with manual transmission .

The bonanza effect is not a technical defect, but a construction-related phenomenon. The engine-gearbox unit installed lengthways rotates in the soft engine suspension and in the soft flexible disks of the cardan shaft , causing periodic acceleration changes to be generated. This soft suspension was and is necessary to keep the strong vibrations of the diesel engines away from the passenger cell compared to the gasoline engine . The fact that Mercedes-Benz is mainly known for this effect is due to the fact that the manufacturer was the only supplier of volume vehicles with rear-wheel drive and diesel engines, with a few exceptions, until the 1980s. The bobbing occurs mainly after gear changes and load changes , especially in full load operation. It is perceived as uncomfortable by the occupants, but can be avoided with a practiced driving style, especially when using the accelerator and clutch pedals.

The problem does not exist with automatic transmissions because the torque converter does not have a rigid mechanical connection between the engine and cardan shaft.

From 1987, the 5 and 6-cylinder naturally aspirated diesel engines from Mercedes-Benz began to combat the problem with an electronic anti-jerk activation ( ARA for short ). Here, a control unit uses a sensor on the flywheel's starter ring gear to monitor the uniformity of the rotational movement of the crankshaft . As soon as vibrations arise, the injection quantity of the mechanical injection pump is briefly reduced by an electromagnet . Since the 1990s, the phenomenon has disappeared thanks to electronic engine controls.

Naming

The name actually goes back to the western series Bonanza of the same name from the 1970s. The reason for this is the characteristic jerking ("gallop feeling") in the load change area when accelerating.

In English one does not speak of the bonanza , but the jig-saw effect (jigsaw effect ).

remedy

There are discussions about remedial measures among self-repairers, especially on the Internet. An improvement is possible by replacing wear parts (see below), but experience has shown that a complete disappearance of the jolting effect is as good as impossible. However, there are also reports of vehicles of the affected series that are not at all affected by the bonanza effect ex works.

The bonanza effect can be mitigated by the following measures:

  • Replacement of engine mounts or dampers
  • Replacement of the cardan shaft joint disks ( Hardy disks )
  • Replacement or overhaul of the injection nozzles
  • Setting the start of delivery
  • Replacing the throttle cable damper

literature

  • Hans-Hermann Braess, Ulrich Seiffert: Vieweg manual automotive technology. 2nd edition, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden, 2001, ISBN 3-528-13114-4