FORD ESCAPE HYBRID E85: ABOUT THE TECHNOLOGY: Sustainable Union
The successful marriage of the two petroleum-saving technologies, hybrid electric power and flexible fuel capability, didn't come without its own unique set of challenges, says Mike Varns, HEV Program Management Team leader for Ford's Sustainable Mobility Technology Lab. "Luckily," he adds, "we were able to take all our FFV experience from past programs and apply it here." Ford has been producing modern FFVs since 1995.
Ethanol, for example, is more corrosive than traditional gas. As a result, the Escape Hybrid E85, a production level gas/electric hybrid Escape, was then retrofitted with fuel and engine system components of corrosion-resistant materials and adhesives. Ethanol also doesn't possess the same energy content or burn rate as gas, which requires the engine to flow more fuel to the injectors to keep performance levels comparable. To handle this increased fuel flow, the Escape Hybrid E85 has a larger fuel pump and larger injectors.
Ford researchers did have to navigate uncharted territory when it came to the Hybrid E85's engine control module (ECM). "An engine that is capable of running on straight gas to E85 has to learn what's in the tank and adjusts accordingly," says Varns.
A vehicle's ECM monitors the exhaust gas sensor and the fuel system's air-fuel ratio, as well as reads the float rod in the fuel tank. When the ECM senses a shift in the engine's air-fuel ratio to the lean side (more air than fuel), it deduces that the vehicle is filled with E85 and adjusts the fuel system accordingly.
"The vehicle learns while the engine is running," says Varns. "But with the hybrid, the engine may be shut off for long periods of time while the vehicle runs on electric power, so we had to make some custom software and calibration changes within the ECM to make sure it could seamlessly remember or relearn the correct percent of ethanol after a shutdown."
The end result is a vehicle that reacts effortlessly and provides the same smooth ride and handling customers enjoy with the gas/electric Escape Hybrid. "We have the same drivability attributes as the conventional gas hybrid," says Varns, "from engine on/off transitions to acceleration and deceleration."