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A flex fuel engine is capable of operating efficiently on any combination of gasoline and ethanol. However, an engine combustion strategy must adapt quickly to a change in ethanol concentration after a refueling event in order to achieve optimum engine combustion. Typical control systems rely on an exhaust gas oxygen sensor (lambda) to measure changes in oxygen concentration following combustion. This feedback control approach can take five to ten minutes to detect the fuel change and correct the combustion strategy. This relatively long lag time could result in suboptimal engine performance such as a loss of engine power, engine knocking, poor cold start performance, unburned hydrocarbons, and high pollutant emissions. To counter this shortcoming, an on-board flex fuel sensor (FFS) was developed to enable a feed-forward control strategy. The FFS may be installed inline between the fuel tank and fuel injector and measure the fuel prior to it reaching the injector.

The center of the Siemens LEV/ULEV-solution is an electronic control unit with a high potential processor, which fulfills all requirements for high calculation accuracy and OBDII-diagnostics. Several new functions were designed on this platform to make sure that the vehicle emissions are low in every operating condition and over the vehicle lifetime. The paper describes the emission benefits of selected new functions and components. Improved fuel preparation with air assisted injectors decreases the engine out emissions and allows a higher spark retardation and a leaner engine mixture without driveability degradation in the catalyst heat up phase. A transient function includes a physical intake manifold model for the calculation of the air amount which enters the cylinder and also a 2nd order wall wetting compensation model. An electrical heated catalyst (EHC) combined with secondary air injection and a multi brick cascade catalyst system.