Experimental investigations on ICE direct start for hybrid powertrains

Due to heave the most powertrain efficiency and carbon dioxide emission savings at hybrid powertrains the internal combustion direct start could be highly beneficial. To realize a safe reliability and low emissions there are an exhaust gas residual depletion at engine stopping phase for inflammation enhancement of the time based combustion and an appropriate fuel metering based on accurate charge estimation of oxygen necessary. For investigating this EGR depletion at engine runout there was an optical high speed measuring system in combination with cylinder pressure indication used in a four cylinder test engine with electromechanical camshaft phasers. After constructing a proper analysis method there were three strategies investigated, which include actuating throttle and camshaft phasing at engine stopping and oscillation phase before standstill, and compared with each other in the matters of EGR depletion, cylinder charge, engine speed deviation (representing NVH) and crankshaft positioning potential.