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The paper presents vehicle-based test work using tri-component, or ternary, blends of gasoline, ethanol and methanol for which the stoichiometric air-fuel ratio (AFR) was controlled to be 9.7:1. This is the same as that of conventional "E85" alcohol-based fuel. Such ternary blends are termed "GEM" after the first initial of the three components. The present work was a continuation of an earlier successful project which established that the blends were effectively invisible to a car using a virtual alcohol sensor. The vehicle used here employed the other major technology in flex-fuel vehicles to determine the proportion of alcohol fuel in the tank, a physical alcohol sensor. Another aspect of the present work included the desire to investigate ternary blend replacements for E85 having low ethanol concentrations. Evidence from the previous work suggested that under specific conditions, ethanol was required in some amount to act as a cosolvent for the gasoline and methanol in the blend.

The paper presents the concept of ternary blends of gasoline, ethanol and methanol in which the stoichiometric air-fuel ratio (AFR) is controlled to be 9.7:1, the same as that of conventional ‘E85’ alcohol-based fuel. This makes them iso-stoichiometric. Such blends are termed ‘GEM’ after the first initial of the three components. Calculated data is presented showing how the volumetric energy density relationship between the three components in these blends changes as the stoichiometric AFR is held constant but ethanol content is varied. From this data it is contended that such GEM blends can be ‘drop-in’ alternatives to E85, because when an engine is operated on any of these blends the pulse widths of the fuel injectors would not change significantly, and so there will be no impact on the on-board diagnostics from the use of such blends in existing E85/gasoline flex-fuel vehicles.