Unique Calibration
The Emission/CAFE/CO2 Compliance Department is responsible for assigning calibration numbers. Unique calibration identifications are assigned to cover similar vehicles to differentiate tires, drive configurations, final drive ratios and other significant certification factors.
These two characters are chosen by the analyst to provide identifiable information unique to each calibration. For example, using the number 2 to denote a two-valve engine and 4 to denote a four-valve engine, provides an easily identifiable difference.