In the quest for lower fuel consumption and emissions, many manufacturers are employing stop/start technology that cuts the engine when the vehicle is stationary. In city driving, this stop/start event may occur several times a kilometre, which is outside the design criteria of a conventional starter motor. To address this issue, manufacturers use units that are designed to cope with the extra starting loads.
Denso has gone one step further and developed a tandem solenoid starter which uses a world-first mechanism that separately controls the forward shift of the pinion-gear and motor rotation. This allows the starter motor to engage smoothly into a still-rotating engine and complete the restart. Denso claims that up to 1,5 seconds can be shaved off the starting time compared with a conventional starter motor in stop/start conditions (i.e. heavy traffic). The demand for stop/start systems is expected to grow as CO2 emissions regulations become even more stringent.