Fading effect la Sandero

Use during downhill grades

Since brakes are normally used for relatively brief periods, they have no active mechanism to eject heat energy except into the surrounding air. Lengthy brake applications, such as during extended downhill grades, may cause more heat to build up than the brakes can bleed off, causing dangerous brake overheating.

Use of engine braking will transfer heat buildup from brake components to the engine, which already has a system to dissipate excess heat energy (most notable component is the radiator).

Disadvantages

Engine braking beyond normal engine drag (i.e., shifting into a different gear only to decelerate a vehicle) can increase the cost of owning and operating a vehicle:

1. It applies stopping forces directly to the drivetrain, transferring wear and tear to parts that are an order of magnitude more expensive and difficult to replace than brake parts.
2. By dramatically increasing engine RPM, it causes additional fuel consumption, even with a fully released throttle, in cars without overrun fuel shutoffs.

Engine braking is always active in all non-hybrid cars with an internal combustion engine, regardless of transmission type. Engine braking passively reduces wear on brakes and helps a driver maintain control of the car. It is always active when the foot is lifted off the accelerator, the transmission is not in neutral, the clutch is engaged and a freewheel is not engaged. This is often called engine drag.

Active use of engine braking (shifting into a lower gear) is only advantageous when it is necessary to control speed while driving down very steep and long slopes. It should be applied before regular disk or drum brakes have been used, leaving the brakes available to make emergency stops. The desired speed is maintained by using engine braking to counteract the acceleration due to gravity.

Improper engine braking technique can cause the wheels to skid, especially on slippery surfaces such as ice or snow, as a result of too much deceleration. As in a skid caused by over-braking, the car will not regain traction until the wheels are allowed to turn more quickly; the driver must reduce engine braking (shifting back up) to regain traction.

The main reason you’d want to employ engine braking is to descend a steep hill. In such a situation, riding the brakes might overheat them and cause them to fade, possibly with disastrous consequences. That said, downshifting by too much for your current speed can be damaging or dangerous as well, so be sure to read your owner’s manual to find out the maximum speed at which you can run in lower gears or with overdrive turned off.

ENGINE BRAKING is a method of slowing down an automobile without the use of the car's friction braking system. It works best on cars with a manual transmission, though cars with automatic transmissions experience the effects as well. Some automatic transmissions may compensate for it to some degree, however, which may not be what you want. In the case of either type of transmission (Though it is more useful with a stick) one can downshift in order to increase the effectiveness of this technique, though it can be observed at any time by simply letting off the gas.

If you let up on the gas in your car you will start to slow down. This is in part due to friction. Let off the gas pedal all the way, and you slow down more than you can explain by loss due to aerodynamics and rolling friction, however. The explanation is that your car is no longer putting energy into causing compression, but the road is. Your engine now works specifically as a compressor, being driven by the road, and going through a fairly significant ratio conversion in the process. The compression (and regular friction of course) creates heat, which is dissipated by the engine's cooling system. However, a lot of the energy is also expressed back into the road via the expansion of gases.

There are a number of reasons you might want to engage in engine braking. The first is that it puts little or no more load on your engine than it would otherwise bear, but saves considerable wear on your brakes. This leads into the next reason, primarily in the case of racing, but also when going down long hills; Frequent use of brakes not only wears out the pads but also heats them up. This leads to brake fade (most brake pads do not grip well when hot) and to boiling of the brake fluid, which does not work properly once it has been boiled. Brake fade is only a problem during overuse of brakes, such as going down long, steep hills, or during "aggressive" driving. The third reason, also primarily significant in sports driving, is that you want to decelerate into turns and accelerate out of them. Downshifting increases the effectiveness of engine braking, and increases the number of RPMs at a given speed, which tends to assist in acceleration.

chestia asta se intampla cand o scoti din viteza.inertia.

dar daca tu crezi ca in motor nu patrunde nici un fel de carburant, si ca admisia e taiata, atunci realizeaza un experiment: mergi cu masina la vreo 60mk/h o opresti o lasi intr-a 4-a si ridici piciorul depe ambreaj(fara sa ai contactul pus. sa ai cheile in mana). sa vedem ce se intampla.daca e cum ziceti voi atunci motorul se va tura pana la 2500 de tura si va realiza frana de motor.

am studiat problema destul de amplu. nu e vb de consum 0. e vorba de o valoare care tinde spre 0 numai daca turatia nu depaseste 1500.dupa pragul de 1500 exista un consum care se apropie de 1.oricum este insignifiant.iar calculatorul de bord va arata tot 0, sau va oscila intre 0 si 1. la relanti este undeva intre 0.7 si 0.9.deci practic cam aceleasi valori.