The hydraulic system is still available, but a previously important component is missing, the brake booster with or without vacuum pump. These functions are integrated into this iBooster, are carried out electrically. This is urgently needed, because the former reinforcement with negative pressure has not been guaranteed everywhere for a long time.

Although negative pressure is still present in the intake stroke of the internal combustion engine, it can not always be tapped. For this purpose, a throttle valve is needed in the intake system, which is only open so far that negative pressure between it and the engine is created and the brake booster can be supplied.

Diesel engines have basically no throttle in the intake tract, only in the recent time one to turn off the engine. In the gasoline engines, there is e-gas nowadays, which also does not always provide reliable negative pressure and a throttling of the engine is now increasingly carried out by the engine control. Therefore, a vacuum pump (picture below) has long been common in diesel engines.

Much more important, however, are now the purely electric vehicles and even more the internal combustion engine temporarily switching off control units. This applies to hybrids driving purely electric, too, and for the recently so popular gliding, so the rolling without motor. Even at start-stop, the brake could lose its power by repeatedly pedaling.

The independence of the negative pressure has changed at the iBooster by dependence on the current. As long as there is enough, you do not have to worry about strengthening the foot force. On the contrary: The iBoost fits much better to the recent ubiquitous recuperation. Between this and the stronger braking, the driver no longer notices a difference.

Bosch speaks of triple redundancy, because on the one hand, the new system can initiate full braking, it remains the opportunity to influence only by foot force and, since only the entire braking force is regulated, the systems for individual wheels remain, such as ABS and ESP.

The iBoost works electromechanically via a two-stage gearbox. Since emergency braking is maintained via the brake pedal, there is still a tandem master cylinder with two circuits, as seen on the compensation tank. The piston rod has kept its connection to the first piston.

In these pictures, an electric motor can be suspected under the housing immediately behind the compensation tank, which drives two gears with a shaft to the left and a worm wheel at the end. With this mechanism can be accessed reinforcing evenly from both sides onto a sleeve around the piston rod.

It is one, only in case of failure of the electronics detachable connection, which gives the electric motor much freedom. Thus, during initial public test runs, the brake application forces could be electronically adjusted, e.g. in a kind of sports position much more aggressively gripping. So the famous knob for the modes will soon affect the brakes as well.