Flex Fuel SensorDescription Downloads Ethanol content is a basis for many functions in an engine. The ethanol content as a variable can be the difference between having optimised ignition timing, fuel injection and boost levels when tuning versus average output when not compensating for the variable. Flex Fuel Manual Features The FuelTech Flex Fuel sensor is the way in which to monitor and vary the ignition timing, fuel injection and boost level based off the ethanol