The AVL-HCLB ( High Compression Lean Burn) Combustion System development work, carried out on a single cylinder research engine and a first generation 4IL engines for passenger car application, has led to intensified R&D acitivity on soma particular features of the AVL System to enable its full fuel economy potential to be realized -while still conforming with current and proposed exhaust emission standards.
It is shown that, compared with cast iron, aluminum is the better cylinder head material also for HCLB engines. A Variable Swirl Intake Port developed at AVL has enabled WOT ( Wide Open Throttle) performance and upper part load NOx emissions characteristics to be improved.
By means of an air flow/fuel flow and engine speed governed engine management system, the upper part load BSFC and NOX emission trade off of the HCLB-englnes has been optimized. An EGR-valve with a non linear flow characteristic has proven to be an important contributing factor in this respect. Finally, SEFI ( Sequential Fuel Injection)-timing strategies are discussed, and their influence on combustion, exhaust emissions and on transient enrichment fuel requirements is shown.