Start-Stop, does it really help?

Is auto stop/start a simple way to conserve gas? Or a more costly upgrade for engines? It’s a debated point, and we’re here to help bring some light to it.

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In automobiles, a start-stop system or stop-start system automatically shuts down and restarts the internal combustion engine to reduce the amount of time the engine spends idling, thereby reducing fuel consumption and emissions. This is most advantageous for vehicles which spend significant amounts of time waiting at traffic lights or frequently come to a stop in traffic jams. Start-stop technology may become more common with more stringent government fuel economy and emissions regulations. This feature is present in hybrid electric vehicles, but has also appeared in vehicles which lack a hybrid electric power train. For non-electric vehicles fuel economy gains from this technology are typically in the range of 3-10 percent, potentially as high as 12 percent. In the United States, idling wastes approximately 3.9 billion gallons of gasoline per year.

Since automobile accessories like compressors and water pumps have typically been designed to run on a serpentine belt on the engine, those systems must be redesigned to function properly when the engine is turned off. Typically, an electric motor is used to power these devices instead.

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With a manual-gearbox car, engine shutdown typically comes with braking to a complete stop, gearbox in neutral and clutch release. Cars with automatic transmissions shut down upon braking to a full stop - the shutdown is activated by the foot brake pedal being in use when the car comes to a halt. If the car is slowed initially by manual use of the automatic gearbox and final stoppage is by use of the handbrake the engine will not shut down.

Automatic stop/start systems do present engineering challenges. The electric starter that was designed to fire your engine a few times a day now has to start the same engine every time the car comes to a full stop. Obviously, a starter that was designed for 50,000 start cycles can't suddenly be responsible for 500K start cycles, so automakers have phased in special starters to better handle the stress.

The frequent cycling can strain internal engine parts, too. Most engine wear and tear happens during startup, so engineers have designed bearings that better self-lubricate and are slicker than normal bearings. Better self-lubrication means the engine will be better protected until pressurized oil arrives after the engine is running. Even without special bearings, engine oil technology has also improved, meaning there's a better layer of protection already on the bearings to prevent excessive wear.

In conclusion it seems to balance out depending on your personal vehicle usage.  With the largest benefits being presented in high traffic areas full of jams and stop lights.

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