Denso Corporation has developed a new tandem solenoid starter, claimed to shave “up to” 1.5 seconds off engine restart time compared to the supplier’s previous models.

Designed specifically for stop/start systems, the system uses a mechanism to separately control the forward shift of the pinion gear and the motor rotation which allows for a quicker restart.

To start the engine, starters shift the pinion gear forward to mesh with the engine ring gear to transmit the rotational force of the starter motor through the pinion gear. The conventional stop/start system starter has a mechanism that conjunctionally shifts the pinion gear and energises the motor for rotation, and is not capable of restarting when the engine is rotating – or while the engine is coasting after the vehicle is stopped.

With the new starter, if the engine is rotating fast, the motor is first energised to increase the pinion gear speed and then the pinion gear is shifted forward when the rotation of the ring gear and pinion gear are close. When the engine is turning slowly enough for the two gears to be connected, the pinion gear is first moved forward, and then the motor is powered.