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Scania Retarder, a short technical history

In the early 1990s Scania applied for a large number of patents on an auxiliary braking system that would become the Scania Retarder, introduced in 1993. It was the first auxiliary braking system with automated downhill speed control, and it was the first to integrate the retarder function in the brake pedal.

The first version of Scania Retarder had a maximum braking torque of 3,000 Nm. The retarder was separated from the gearbox, mounted on the chassis and connected to the gearbox with pipes.

From its beginning, the retarder could be engaged in two ways: via a lever on the instrument panel, or – the more ingenious solution – by pressing the brake pedal down one centimetre. The lever had five positions, and the last position activated the exhaust brake.

The downhill speed control, which was activated by pressing the end of the lever or by slightly pressing the brake pedal, tried to keep a constant speed downhill by automatic use of the retarder and the exhaust brake.

In 2006, Scania launched a new generation of gearboxes in which Scania Opticruise – an automated gearchanging system – and an updated Scania Retarder were completely integrated. Scania Retarder’s braking torque grew from 3,000 Nm to 3,500 Nm and the braking power at low revs had increased by 40 percent, creating a drastic improvement at low speeds.

Scania’s electronically controlled braking system, which was introduced in 1996, paved the way for a solution to help drivers maintain a stable speed. By integrating Scania Retarder, Scania Opticruise, the exhaust brake and the conventional braking system, the vehicle could maintain a stable speed regardless of the environment.

A couple of new functions became possible with the new CAN-bus based electrical system in the R-series introduced in 2004. It became possible to use the wheel brakes together with the retarder to increase comfort and minimise wear on the brake linings. If, for example, a vehicle is driven downhill at low speed the retarder may not be enough to maintain the speed and, as a consequence, the exhaust brake must be activated.

Should even more braking power be necessary, Scania Opticruise changes down to increase engine speed with a resulting increase in exhaust brake power.

To stop the vehicle from picking up speed during downchanges when the exhaust brake is inactive, Scania Retarder and the wheel brakes work together to maintain a stable speed. This also makes it easier for the automated gearchanging system to work.

The brake blending feature maximises the amount of retarder braking in relation to the retardation requested by the driver via the brake pedal and thus minimise wear on the wheel brakes.

A more powerful Scania Retarder was launched in 2012, with braking torque of

4,100 Nm and dramatically increased low-rev performance.