DefinePK

Abstract

Engine optimization is one of the most cost-effective methods in reducing emissions and fuel consumption. In the theory, the maximum overlap would be needed between the intake valves and the exhaust valves opening whenever a common internal-combustion engine is running at high revolution per minute (RPM). At lower RPM, however, as the engine is run at lighter load, maximum overlaps may be useful as a means to lessen the fuel consumptions and emissions. The timing of air intake and exhaust valves are usually determined by the shapes and the phase angles of the camshaft. To optimize the air breathing, an engine would require different valve timings at different speeds. As the revolution speed increases, the duration of the intake and exhaust valves opening would decrease, thus less amount of fresh air may enter the combustion chambers, while complete exhaust gas cannot exit the combustion chamber in time. Therefore, varying the intake timing of an engine could help to produce more power and, if applied to smaller and lighter engine, it could result in a lower fuel consumption as well. This particular investigation has been conducted through simulations and complemented by experimental works. It has been realized in this study that optimization of an engine together with implementation of variable valve timing was able to generate similar power with an increase in volumetric efficiency, while it is obtained with a slightly lower fuel consumption. As reported by many researchers, the variable valve timing method has been indeed proven to deliver better fuel economy, less emissions, but higher torque under any operating condition.