A method of lean air-fuel ratio control using combustion pressure measurement Lee, Albert T.; Wilcutts, Mark; Tunestål, Per; Hedrick, J. Karl General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.• Users may download and print one copy of any publication from the public portal for the purpose of private study or research.• You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal Take down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. AbstractIn this paper a method for control of air-fuel ratio (AFR) in cold or lean-burning spark-ignited engines is investigated. The technique uses combustion pressure as measured by a cylinder-mounted sensor, and is based on the phenomenon of increasing cycleto-cycle combustion pressure variation as the air-fuel mixture approaches the limits of flammability. The cylinder pressure is measured from one engine cycle to the next, and large drops in mean effective pressure (IMEP) are used as an indicator of poor combustion. In response, the airflow or fuel flow to the engine can be manipulated. In a series of experiments, the air and fuel are alternately investigated as control inputs, and performance compared. The resulting control system is a high-bandwidth AFR control strategy that can be used under cold or lean conditions when conventional exhaust gas oxygen sensor cannot be used. Moreover, the method is directly tied to the combustion process and the relevant performance measure F combustion stability F that is perceptible to the driver as a rough-running engine. r