With the wider use of biofuels in the marketplace, a program was conducted to study the deposit forming tendencies and performance of E85 (85% denatured ethanol and 15% gasoline) in a modern Flexible Fuel Vehicle (FFV). The test vehicle for this program was a 2006 General Motors Chevrolet Impala FFV equipped with a 3.5 liter V-6 powertrain.
A series of 5,000 mile Chassis Dynamometer (CD) Intake Valve Deposits (IVD) and performance tests were conducted while operating the FFV on conventional (E0) regular unleaded gasoline and E85 to determine the deposit forming tendencies of both fuels. E85 test fuels were found to generate significantly higher levels of IVD than would have been predicted from the base gasoline component alone. The effects on the weight and composition of IVD due to a corrosion inhibitor and sulfates that were indigenous to one of the ethanols were also studied.
Testing showed that the IVD generated from E85 could be controlled or eliminated by using Deposit Control Additives (DCA). The results of this study provide a method for controlling IVD generated in FFVs operating on E85. Although sulfate deposits were detected on fuel injector valves with ethanol containing 4 ppm sulfates, they did not cause fuel injector performance issues in the 5,000 mile tests.
FFV vehicle performance testing showed fuel economy losses consistent with E85's lower energy content compared to conventional gasoline, but the E85 fuel provided an increase in power.