VS - Electrical Systems From Stop-Start to Hybridization

Stop-start function is a concrete answer to reduce CO 2 emissions and fuel consumption adapt the Stop-Start function to a given situation and according to many parameters. A major parameter is the engine temperature. A certain percentage of fuel is consumed to overcome friction in powertrain, to enhance vehicle efficiency a reduction of friction is crucial; to achieve this the oil viscosity (temperature) must be optimal. As major part of the pollutants is emitted after starting the vehicle, the very first action is to reduce the oil viscosity by accelerating the engine warm up, the ten first minutes are crucial. Bringing vehicle oil to an optimal operating temperature, and maintaining it is the first step to reducing fuel consumption and CO 2 emissions. Some techniques help in reaching optimum oil operating temperatures, the most common and historical technique is to bypass the coolant circuit radiator, this is part of the role of the engine cooling loop thermostat. Oil coolers are common on engine, they are able to work in both directions, having the ability either to cool the oil but as well to heat the oil by exchanging heat with the coolant, they are as well used to speed up the oil temperature raise.

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What are Stop-Start benefits? The reduction of fuel consumption, greenhouse gases and pollutant emissions is one of the major challenges that the automotive industry faces today. Automakers are making massive R&D investments in a bid to improve the efficiency of their engines. But progress is only made in small steps. Since, in city driving, vehicles are at a standstill for almost 35% of the time, during which the engine idles needlessly, the benefits of the Stop-Start system are quite obvious. This system switches off the engine when the vehicle stops, at a traffic light, for example, and starts it up again as soon as the driver asks for power. The benefits of Stop-Start systems are highly depending on the driving cycle that is considered. Considering the only urban portion of the NEDC fuel economy reach 15%, rising to 25% in real conditions of traffic jam. A common question from end customers on the Stop- Start function efficiency relates to some thoughts on fuel over consumption when restarting an engine. Internal combustion engine are still governed by the same thermodynamic laws and restarting a machine always require energy, but enginemanagement have notably evolved, allowing today some advanced injection processing to speed up the cranking phase. This is further completed by complex strategies to On a global NEDC cycle, Stop-Start systems represent between 4 to 5% fuel economy.

Stop-Start systems are only activated after engine heat-up completion.

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