Ethanol can be converted into a 1:1:1 mixture of H2, CO, and CH4 at 300°C using a copper-nickel catalyst, a process known as “low-temperature ethanol reforming.” The hydrogen content of this mixture enables an engine to operate lean or with high levels of EGR, improving fuel economy and emissions. An onboard ethanol reformer- a catalyst module providing heat exchange with exhaust-was recently reported and shown to exhibit stable high conversion of ethanol driven by exhaust heat.This paper describes the successful integration and operation of a Ford 3.5L 3 TiVCT flex-fuel engine with a compact reformer and auxiliary hardware, fueled by E85. The system constitutes an integrated power system suitable for vehicle integration.The engine was operated on a mixture of E85 and reformate using a stoichiometric air-fuel ratio with internal EGR at a 12:1 compression ratio. At the worldwide mapping point, 1500 rpm/2.6 bar BMEP, use of 25% reformate in the fuel enabled stable engine operation with extreme valve overlap (50° EVO /40° IVC) and delivered efficiency improvement of about 10% over E85 alone. At idle (600 rpm/ 0.7 bar BMEP) using 40% reformate in E85 with 30° EVO provided a 12.3% efficiency improvement.A lightweight “shoebox” reformer design provided stable operation while producing only minor exhaust backpressure. The system also included an exhaust diverter valve to control reformer temperature and a buffer tank with automated drain to provide a reserve of dry reformate for cold start and engine transients.