Do stop-start systems wear out your automobile’s starter?

Some are almost unnoticeable, others make the automobile shudder every time they activate—but stop-start systems are here to remain.

First rolled out in Europe and Asia, where crowded city driving requires cars to spend more time at a standstill, they switch off the engine when the automobile’s not moving. When the driving force starts to lift a foot off the brake pedal, they quickly restart the engine in time for the automobile to maneuver away from a stoplight or traffic jam.

Most such systems already keep the automobile’s accessories—lights, wipers, audio system, climate control—operating as standard. That limits the period of time the engine can remain off, generally to a period between 45 and 90 seconds. But in stop-and-go traffic, that is often enough to save significant amounts of fuel.

Stop-start systems were slower to return to the U.S., partially because they didn’t provide much advantage even within the EPA’s city-driving test cycle. Several years ago, Mazda’s Robert Davis suggested that the advantage might amount to 0.1 mpg on the EPA city cycle, an improvement that might be achieved at less cost using different technologies.

However the essential query most automobile buyers have about recent stop-start systems is: won’t they wear out my automobile’s starter motor?

The reply is not any.

For a proof of why, we reached out to a source within the auto industry who’s had an important deal of experience with these systems. This person asked that we keep him anonymous for a wide range of reasons, amongst them that his current employer hadn’t approved his comments.

“Automotive engineers don’t use ‘traditional’ starter motors in these situations,” he explained. “The starter used for stop-start systems combines several technologies.”

What follows is his explanation of those technologies, evenly edited by Green Automobile Reports for clarity and elegance.

(1) The gear ratio from the starter-drive pinion to the flywheel ring gear is optimized to make the starter’s motor turn more slowly. This will be refrained from materially changing the design of the transmission or flywheel in any respect on existing designs.

Crucially, this reduces starter-motor speed (in RPM), since 90 percent of starter-motor brush wear occurs not during cranking, but through the coast-down after the beginning has finished. If a higher-torque motor can spin more slowly, its coast-down time is shorter, increasing its longevity.

(2) The composition of the carbon and copper brushes on a stop-start motor differs from its traditional counterparts to increase longevity without accelerating the damage on the commutator.

(3) Moderately than depend on oil-impregnated bushings for the rotating assemblies, stop-start starters mostly use needle bearings.

 (4) The solenoid on stop-start starters decouples the mechanical motion of engaging the drive pinion into the flywheel from the electrical motion of stopping and starting the motor.

This permits for a dedicated design to show power on and off to the motor, optimizing contact design and wear, against contacts that must be integrated as a part of a spring-loaded plunger.

This also reduces the electrical load requires to show the engine, in order that there’s enough current available for accessories/lighting to operate through the start event.

(5) Finally, stop-start motors are integrated with other technologies that discover when each cylinder of the engine will reach top-dead center.

That lets the fuel injectors pulse and fire through the middle of a whole rotation of the crank, against having to attend for an entire revolution that lets the primary cylinder reach that position to start out the fuel-spark timing sequence.

And there you’ve gotten it: the total technical explanation of why you need not worry about starter motors wearing out prematurely attributable to stop-start systems.