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Butanol, which can be produced from biomass, has been suggested as an alternative to ethanol, due to its higher energy density, lower oxygen content and more favorable hygroscopic and corrosive properties. In the Czech Republic, E85 is widely sold at fuel stations and used in ordinary vehicles, both with and without aftermarket control units. This work investigates the potential of ordinary automobiles to run on butanol, and the associated effects on exhaust emissions under real driving conditions. A Škoda Felicia car with a throttle body injection and a Škoda Fabia car with a multi-point port injection have been run on gasoline and its mixtures with up to 85% volume of ethanol, of n-butanol, and of isobutanol (2-methyl-1-propanol). An auxiliary control unit has been used with higher alcohol content. On each fuel, each car was driven 5-6 times along a local test route.

An ordinary, unmodified port fuel injection spark ignition automobile engine with closed-loop air-fuel ratio control and a three-way catalyst was operated on two butanol isomers, n-butanol and iso-butanol, and their blends with gasoline at steady-state operating points covering both common and potentially problematic regimes. The engine control unit was able to maintain the air-fuel ratio while running on both butanol isomers and their blends with gasoline. Only small changes in the heat release rates, small and insignificant decrease in exhaust gas temperatures, and no excessive increase in emissions were observed. Under commanded enrichment operation, the maximum torque, air-fuel ratio and exhaust emissions were comparable among nearly all fuels tested. The exhaust gas temperatures were comparable among fuels, with a moderate increase observed in some regimes during operation with high share of n-butanol in fuel.