A Comparison of the Effect of E85 vs. Gasoline on Exhaust System Surface Temperatures

With concerns over increasing worldwide demand for gasoline and greenhouse gases, many automotive companies are increasing their product lineup of vehicles to include flex-fuel vehicles that are capable of operating on fuel blends ranging from 100% gasoline up to a blend of 15% gasoline/85% ethanol (E85). For the purpose of this paper, data was obtained that will enable an evaluation relating to the effect the use of E85 fuel has on exhaust system surface temperatures compared to that of regular unleaded gasoline while the vehicle undergoes a typical drive cycle. Three vehicles from three different automotive manufacturers were tested. The surface of the exhaust systems was instrumented with thermocouples at specific locations to monitor temperatures from the manifold to the catalytic converter outlet. The exhaust system surface temperatures were recorded during an operation cycle that included steady vehicle speed operation; cold start and idle and wide open throttle conditions. This drive cycle was run two times on each vehicle while temperature data was collected with the vehicle operating with regular unleaded gasoline and then with the vehicle operating on fuel blends of 85% ethanol/15% gasoline. The data was plotted and analyzed with results and conclusions presented for consideration.