Engine management for Flex Fuel plus compressed natural gas vehicles

Ethanol has been used in Brazil as a passenger vehicle fuel since 1979. Until the year 2000, vehicles were made to run exclusively with either gasoline or ethanol. The MultiFuel engine control module (ECM) was developed allowing vehicles to use fuels with any ethanol percentage, relying only on the existing oxygen sensor as opposed to an add-on ethanol sensor for the percent ethanol evaluation. The use of tank fuel level information allowed for far more robust ethanol percent detection and improved drivability. Four years later, compressed natural gas (CNG) capability was integrated into the MultiFuel technology. Prior to that, vehicles using CNG normally required a second ECM. The MultiFuel integrated with CNG capability is known as the Tri-Fuel system. It uses only one ECM, seamlessly controlling both liquid (ethanol blends and gasoline) and CNG fuels with little power loss, and excellent drivability and fuel consumption. This paper will present both the MultiFuel and Tri-Fuel technologies.