IMPROVED METHOD OF CONTROLLING ENGINE DURING SCAVENGING

In an engine system, a method of determining the value of the air fuel ratio in an engine cylinder AFR Combustion Chamber when under scavenging conditions comprising; a) measuring or estimating the engine speed; b) measuring or estimating the inlet pressure; c) determining a value for the Air Trapped Ratio based on the results of steps a) and b); d) determining the air/fuel ratio at a location downstream of the cylinder/in the exhaust (AFRex); d) determining AFR Combustion Chamber = Air trapped Ratio * AFRex