Burkhard, J., "Individual Cylinder Fuel Control for a Turbocharged Engine," SAE Technical Paper 2014-01-1167, 2014, doi:10.4271/2014-01-1167.
This paper discusses on-engine results achieved in applying an algorithm-based Individual Cylinder Fuel Control (ICFC) to turbocharged four-cylinder engines.ICFC is a software algorithm which permits the detection and closed-loop correction of air/fuel imbalances on a cylinder-by-cylinder basis, which is not possible with typical bank-wide closed loop fuel control systems. Cylinder-to-cylinder air/fuel imbalances can be the result of a number of combined sources. The potential sources include fuel injector variation (both new and aged) as well as maldistribution of fresh air airflow, evaporative emissions purge flow, or exhaust gas recirculation flow. The ICFC algorithm requires no additional hardware beyond the typical sensor set already present on modern automotive spark-ignition engines, including oxygen sensor(s) and engine controller.While the ICFC algorithm has been employed in production programs since 2009, to date these have all been naturally-aspirated engines using switching oxygen sensors. With increasingly stringent worldwide emissions and fuel economy standards, the demand for both turbocharging and WRAF (wide-range air/fuel) oxygen sensor technologies in the light-duty passenger vehicle market has grown.In this investigation, the ICFC algorithm was applied to and verified on two different turbocharged engines, one with switching oxygen sensor feedback, and the other with WRAF oxygen sensor feedback; in both cases the oxygen sensor was located downstream of the turbine outlet. It was demonstrated on these engines that the ICFC logic is capable of correcting cylinder-to-cylinder air/fuel imbalances through adaptive learning, despite the potentially disruptive effects of the turbine in the exhaust stream, and with either type of oxygen sensor.