Artigo:

A great part of the projects in the engine design field are today facing new challenges in the basic engine design and calibration area. Most of the efforts have been driven by new emissions level regulations, which have become more and more demanding. Although the use of Exhaust Gas Recirculation (EGR) is nowadays often used for automotive Diesel engines to achieve NOx levels complying stringent legislations requirements, such as MAR-I, electronically controlled external EGR systems still presents an expensive technology, often unsuitable for small Diesel engines for off-road applications. An interesting and cost effective solution towards meeting those new emission requirements for smaller Diesel engines is the so-called internal EGR, which is obtained by modifying the valve train system. Among some few possibilities found in the market, one can add an extra intake valve lift event during the exhaust stroke in order to increase the level of exhaust residuals in the cylinder. That increased amount of gases with reduced concentration of O2 and increased concentration of CO2 contributes mainly to reduce the in-cylinder average temperature, which then reduces the NOx formation rates. That allows advancing of the start of combustion in order to reach very competitive fuel consumption. It has been researched and applied the internal EGR technology, so that a sufficient amount of exhaust gases is able to flow back to intake manifold, and finally fill the cylinder together with upcoming cooled air charge of the subsequent stroke. This technology is also known as AVL TINER® system, which stands for Technology for In-cylinder Nitrogen oxides Emission Reduction.