전륜 구동 차량을 위한 저중속 토크 향상 배기계 개발

다국어 초록 (Multilingual Abstract)

Recently, many technologies are being developed for better fuel economy. Especially, car producers try to cut fuel consumption in city driving. It is possible to reduce automatic transmission(AT) gear shifting which worsens fuel economy if the engine gets higher low/mid range torque. So there is a growing tendency to apply dual continuous variable valve timing(CVVT) direct injection spark ignition(DISI) engine for this. Since exhaust and intake valve are under control of dual CVVT, its possible to improve low/mid range torque by utilizing overlap period. And DISI engine can minimize the problem with fuel oxidation in catalytic converter occurred as extending overlap period in the multipoint injection(MPI) engine because it directly sprays with fuel in the cylinder and controls a spraying- time point. But exhaust gas interference produced by explosion of the fuel in cylinders should be minimized to utilize overlap period. The more the distance between exhaust valve and exhaust junction is extended, the more exhaust gas interference is reduced. Front wheel drive(FWD) vehicle with disadvantage in packaging has worse low/mid range torque than rear wheel drive(RWD) vehicle . There were several cases to increase the distance in FWD vehicle. But they needed to accept disadvantages such as reducing size of other parts to place two bellows or deteriorating isolation performance because of eliminating a bellows. In this paper, the new exhaust system improving low/mid range torque by reducing exhaust gas interference in the FWD vehicle equipped with dual CVVT DISI V6 engine is studied. This new exhaust system with new type of bellows and semi-circular pipe keeps the existing performance as well as moves the junction 621mm to the rear. As the result, its verified that low/mid range torque is improved by 5%~6% and fuel efficiency by 0.3%~1.0% and driving performance by 1.7%~2.5%.