Ethanol Powered ATV

The idea behind this project was to demonstrate the potential benefits of modifying a small engine (like those in ATV's) to better utilize ethanol-blend fuels. While E-85 is readily available for flex-fuel vehicles (FFV) at lower cost than standard gasoline, FFV get lower mileage burning E-85. But, this lower mileage is not entirely due to the lower BTU content of ethanol. FFV engines are designed to run most efficiently on gasoline. Their design and tuning are suboptimal for E-85. Engine modifications would make engines more efficient burning E-85 exclusively.

The higher octane of E-85 (100+) allows it to be used in a high-performance engine, which produces more output from a given BTU input. Performance-enhancing engine modifications make the engine more optimal for E-85 and realize benefits of ethanol fuel. The hope was to modify the engine so that it would produce more horsepower and torque while decreasing fuel consumption.

In September Arctic Cat donated a Prowler Utility Terrain Vehicle (UTV) and a spare engine to be used for modification and testing. Research was conducted as a partnership between Northwest Technical College’s (NTC) High-Performance Engine Machinist Program and Arctic Cat, involving faculty, students and Arctic Cat employees. A baseline test of the stock engine was conducted using regular unleaded gasoline and a dynamometer (dyno) to test the fuel consumption, horsepower, and torque.

After the baseline performance of the machine was established the engine was disassembled and modified to run using E-85 fuel. Repeating the same tests as before, the modified engine produced more horsepower and torque. Fuel consumption was also calculated in the same manner as before.

The engine was then modified to raise the compression ratio to approx. 11.58:1.  The engine was then reassembled and the program from Speedwerx was installed.  The engine was then tuned to run on E-85 for maximum power. 

Our mileage test was done on a mustang chassis dynamometer by running the vehicle at 30 mph in high gear for exactly one minute at 55 percent throttle and weighing the fuel tank throughout the test to determine fuel consumption. This was done by having a spare tank to have placed on a scale.

The throttle position was determined using a Speedwerx programmer that was borrowed for this project. The baseline test using gasoline netted a 5 gram consumption average over 4 tests. On gasoline, the prowler made a consistent 33 HP, and 32 lb. ft. of torque.

The engine was then disassembled and machined .040 off the bottom of the jug to raise the compression ratio to approx. 11.58:1. The engine was then reassembled and the Speedwerx programmer was installed again. The engine was then tuned to run on E-85 for maximum power. Upon driving the prowler on the ethanol fuel, it accelerated much faster and seemed to have more power in the lower RPMs. It had an average consumption over 4 tests of 8.2 grams of fuel consumed on ethanol and it produced a solid 36 HP and 34 lb. ft. of torque.

The overall impression of the performance of the vehicle after the modifications were done was positive. The person who test drove it reported that it had much more power in the lower RPMs and had quicker throttle response.