Individual Cylinder Fuel Control for Imbalance Diagnosis 2010-01-0157
This paper identifies a select method for performing cylinder imbalance measurement, correction and diagnosis. The impetus is to address new U.S. Federal regulations that require the detection of excessive cylinder air-fuel ratio (AFR) imbalance, and doing so requires the foundational ability to measure and preferably remove cylinder imbalance via active closed-loop control. This function is called Individual Cylinder Fuel Control (ICFC).
ICFC starts by extracting cylinder-imbalance information from the front oxygen sensor, and that information comes in the form a of continuous data stream. That stream is then parsed to create virtual sensors- one for each cylinder. Each virtual sensor acts as an imbalance or error signal which ICFC uses to correct and learn via feedback and feed-forward control for each cylinder.
The cylinder imbalance diagnostic is enabled by the presence of ICFC. The diagnostic continuously monitors to determine if ICFC is operating within its control authority, or if sufficient imbalance may exist to exceed a multiple of the applicable FTP emissions standard. Implementation of the diagnostic adds a subcategory to our existing Fuel System Diagnostic structure and reuses the common function-calling and accounting mechanisms to satisfy all of the fuel system monitoring requirements.