John Deere introduces mower that runs efficiently on E0 to E85

By Susanne Retka Schill | July 19, 2013

John Deere has introduced a flex-fuel model to its ZTrak line of commercial lawn mowers.  The new, industry exclusive, Z925M Flex Fuel is compatible with the full range of fuels from E0 to E85 and delivers improved horsepower, torque and fuel efficiency.  

“The flexibility to run machines with fuel blends ranging from straight gasoline up to 85 percent ethanol will appeal to customers who want to be more green, burn less fossil fuel, and still have multiple fuel options available,” said Chase Tew, product marketing manager for John Deere Commercial Mowing.

The new model is a 24.6 horsepower commercial-grade mower, with either 54- or 60-inch blades. It is powered by an aluminum block, air-cooled, vertical shaft, electronically fuel injected engine. Tew explained the engine’s improved horsepower, torque and fuel efficiency is a result of a closed loop electronic fuel system, which uses an oxygen sensor to continuously monitor oxygen levels in the exhaust gas. 

“Along with other continuously monitored data such as intake air pressure and temperature, oil temperature, engine speed, crankshaft position, and throttle position, the Flex Fuel Electronic Control Unit (ECU) continuously calculates the optimum amount of fuel to inject to maximize power, torque and fuel efficiency,” Tew told Ethanol Producer Magazine. “If the oxygen level in the exhaust strays from the ideal air/fuel mixture, the oxygen sensor triggers adjustments to the amount of fuel injected into the system. The engine then ‘closes the loop’ between the air/fuel intake mixture and the exhaust gas output to provide a constant stream of critical feedback to deliver optimal fuel efficiency and improved power with any fuel blend being used.”

As a flex-fuel engine, Tew explained it could not be optimized to take full advantage of ethanol’s positive properties such as the 100 octane antiknock rating, since it would then not be able to use straight gasoline. “However, the flex-fuel system continuously optimizes performance and efficiency as much as possible for all fuel blends being used.”

The specifications sheet for the new mower says the flex-fuel engine delivers up to 25 percent better fuel economy than typical carbureted engines of similar power at 1.1 to 1.9 gallons per hour. “Fuel consumption depends on many factors such operating conditions, operations being performed, loads, terrain, deck size, blades, and other factors such as fuel types,” Tew explained. “Because of the lower amount of energy per gallon of ethanol, higher blend ratios of ethanol will result in proportionately higher fuel consumption.  However, keep in mind that higher ethanol blend fuels also cost proportionately less than gasoline.”

The engine also has cleaner emissions, Tew said, due to ethanol’s greenhouse gas emission profile that is about 40 percent lower than gasoline. “The flex-fuel engine also has lower HC (hydrocarbon), NOx (oxides of nitrogen), and lower CO2 (carbon dioxide) emissions when running on E85 fuel.”