Siemens VDO has set up a demonstration vehicle with a direct injecting (DI) gasoline engine to evaluate different stop/start strategies to reach future CO2 targets. The vehicle is equipped with both a belt-alternator-starter (BAS) system and a conventional starter. Both starter-technologies are combined with a so-called start-optimization strategy, implemented in the engine control unit (ECU). The possible combinations between the applied starter technologies and the ECU start strategies are evaluated in view of stop/start requirements.
The start-optimization strategy is based on injection and ignition upon start request, prior to synchronization at the tooth gap of the crankshaft target wheel. The strategy is realized on a vehicle with a DI engine. To demonstrate the potential of that start strategy also for an engine with port injection (PI), the expected start time behavior is simulated.
To optimize the engine start the knowledge of the absolute engine stop-position is required by the ECU. For that purpose, Siemens VDO developed a new bidirectional crankshaft sensor, for tooth- and direction detection on toothed - or encoded target wheels.
Experimental results obtained on a DI engine show the benefits of this solution in terms of starting time, quality of start reproduction and fuel economy.