moottorijarrutuksen

Moottorijarrutus, also known as engine braking, is a technique used in manual transmission vehicles to slow down the vehicle by using the engine's resistance to rotation. Instead of solely relying on the service brakes, the driver downshifts to a lower gear. This causes the engine's revolutions per minute (RPM) to increase, and the engine's internal friction and the resistance of the pistons moving against the compression stroke oppose the vehicle's forward motion, thus slowing it down.

The effectiveness of moottorijarrutus depends on the gear selected and the vehicle's speed. Downshifting into a lower gear at higher speeds will result in more pronounced engine braking. This method is particularly useful for controlling speed on downhill descents, preventing brake fade, and reducing wear on the service brakes. It can also be used in conjunction with service brakes for quicker deceleration.

Proper application of moottorijarrutus involves selecting a gear that is appropriate for the current speed to avoid over-revving the engine, which could cause damage. While automatic transmissions have features that simulate engine braking, true moottorijarrutus is primarily a manual transmission technique. It is a common practice in many countries, particularly in Europe, and is often taught as part of driver education.