Moottorijarrutuksella

Moottorijarrutus, also known as engine braking, is a technique used in driving where the vehicle's engine is used to slow down the vehicle instead of relying solely on the service brakes. This is achieved by downshifting to a lower gear. When the driver takes their foot off the accelerator and downshifts, the engine's internal friction and the resistance of the drivetrain components create a braking effect. The engine acts as an air compressor or a pump, converting the vehicle's kinetic energy into heat and sound, thus slowing its momentum.

The effectiveness of moottorijarrutus is dependent on the gear selected and the engine speed. Lower gears and higher engine revolutions per minute (RPM) result in stronger engine braking. This technique is particularly useful in certain driving situations. On downhill descents, it helps to maintain a controlled speed without overheating the service brakes, which can lead to brake fade. It can also be used to reduce wear on the service brakes during normal deceleration.

In manual transmission vehicles, moottorijarrutus is a natural consequence of shifting gears. In automatic transmissions, some systems offer a manual or sport mode that allows the driver to select lower gears, enabling engine braking. Some modern vehicles also have electronic systems that can automatically engage engine braking when the driver lifts off the accelerator. Proper use of moottorijarrutus can improve fuel efficiency by reducing the need for braking and coasting, and it can contribute to safer driving by providing an additional layer of speed control. However, excessive or abrupt engine braking, especially on slippery surfaces, can potentially lead to loss of traction.