Turf Magazine - October, 2008


Propane Power

New engine for commercial mowers
By Patrick White

Gasoline is such a part of our lives that it’s sometimes difficult to imagine what we’d do without it. But, increasingly, our minds are being expanded. “Alternative fuels” has become a commonplace phrase in news reports, political discussions and even tailgate talks on the job. Whether the concerns are related to high cost, shrinking supply or the environment, individuals, businesses and governments are looking for new fuel solutions that can substitute for gasoline.

It’s not just automobiles involved in the alternative fuels arena, Briggs & Stratton recently developed a propane-powered engine for use in commercial mower applications. The primary goal was to produce a low-emissions engine (the World LP Gas Association states that “compared to gasoline, propane yields 12 percent less carbon dioxide, 20 percent less nitrous oxide, and as much as 60 percent less carbon monoxide) that would allow commercial lawn care companies to operate freely in the growing number of cities that have instituted “Ozone Action Days,” banning the use of commercial mowers after 1 p.m. At the same time, the engine would have to live up to the expectations of commercial end users in terms or power, performance and reliability.

While there have been a variety of efforts in the lawn and landscape industry in the past to convert existing engines to use propane fuel, the Briggs & Stratton effort represents an engine built by the factory specifically for propane. It started with a proven base package: the Briggs & Stratton Vanguard Big Block V-Twin engine. With more than 50,000 Big Block engines already in use, the durability and reliability of the engine were known qualities. The next step was to undertake the necessary engineering changes and testing to produce an engine tailored for use with propane.

“The Vanguard Big Block was the perfect engine to work with,” says Mike Braun, product manager with Briggs & Stratton, who worked on the project. “There were many improvements made when we designed that engine; it was built nice and robust, so the propane was a good fit.” He adds, however, that during the propane engine’s development, there were some basic changes that were made: “We ‘stress-relieved’ all of the castings to ensure good, precision machining. We used iron exhaust valve faces to provide endurance, and a specially designed carburetor designed for use with propane. The ports are different, the jetting is different.”

The development of the engine was a joint project between Briggs & Stratton and Ferris, and the propane engine is currently available on the Ferris IS 3100ZP zero-turn mower. Briggs & Stratton’s Engine Application Center in Milwaukee, Wis., was tapped to help apply the knowledge developed in building the generator engines and make it work with a commercial zero-turn mower. Ferris took a lead role in the development and testing, which took place in Florida. “We all sat at the table and used our resources to audit the overall design and test the ideas to be sure it would work,” says Braun. “Every time we got test results back, we learned more and more about integrating the engine and the mower.”

Photo courtesy of Ferris.
The Ferris IS 3100ZP zero-turn mower is powered by a Briggs & Stratton Vanguard Big Block propane engine.

Briggs & Stratton offers standby generators for homes that are powered by natural gas, so the company is not new to the concept. Braun says one of the challenges was to take that propane engine technology and adapt it to the special circumstances encountered in commercial mowing, namely the bouncing, turning, and ups and downs. “We had to make sure we had the proper withdrawal system from the tanks,” he explains. “We used special ‘vapor withdrawal’ [as opposed to ‘liquid withdrawal’] fuel tanks to ensure consistent, hassle-free operation. We set the ‘pick-ups’ in the tanks so that they would always be withdrawing vapor; there will never need to be liquid going through the regulator into the carburetor.”

Visually looking at the propane engine itself, users will notice a few differences. “One nice thing is that there is no choke on the system,” says Braun. “It might seem strange on a commercial unit to not see a choke, but the propane system doesn’t need one.”

There are additional ways in which the propane engine is simpler to operate and maintain. “With gasoline engines, we try our best to adjust carburetors to work well with different gasoline volatility levels, which change over time and with different seasons and in different areas of the country,” says Braun. “There are summer blends, winter blends, different ethanol blends and so on. With propane, you don’t need to worry about that. The fuel is very consistent.” Briggs & Stratton was better able to dial in the calibration of the carburetor for optimal performance.

In addition to producing fewer emissions while running, the propane engine is more environmentally friendly from a fueling standpoint. “There is a lot of evaporative emissions that happen with gasoline, and people often spill it,” says Braun. “With the propane engine, the way the tanks are connected and disconnected is much friendlier in that regard. There is very little chance to create emissions from spilling.”

Dan Roche, marketing manager for the Briggs & Stratton Commercial Engine Division, says the company is working to promote the benefits of the propane engine to its customers; and for many, it’s a new concept. “I think for most of our commercial customers, the biggest concern has to do with power. They want to be sure the engine is powerful enough to cut thick, wet grass,” says Roche.

In large measure, any such questions are answered by the base Vanguard Big Block engine. “The large displacement brings the torque that gets the job done. That’s what keeps the deck spinning, keeps the wheel motors moving, and keeps lawn care companies productive,” Roche says. Briggs & Stratton rates the engine in terms of displacement (the volume is 895cc) rather than horsepower.

To assure commercial users of the performance and reliability of propane-power engines, Briggs & Stratton points to the longtime use of this fuel in forklift applications. “Forklifts are heavy-duty pieces of equipment, just like commercial mowers. They’re relied upon by businesses, just like commercial mowers. And, they have a long track record of being very safe and efficient,” says Roche.

The other area where perspective users have questions has to do with “fuel handling,” says Roche. “Gasoline is a volatile fuel, but we all handle it so frequently that we’re comfortable with it. People are familiar with it,” says Roche. To help promote greater understanding of propane as a fuel source for its engines, Briggs & Stratton is working with the Propane Education & Research Council to help develop educational and training materials. “We’re working very closely with them. We know this is a new fuel for people to work with, and we want to make sure we’re providing all of the necessary safety and handling instructions in all of our manuals and literature.”

Roche says that even those just hearing about propane-powered mowers have some understanding of the benefits of propane. “They view it as a ‘clean’ fuel. To them, that means there are no ‘Ozone Action Days’ to slow down their business. And, propane is known as a fuel that ‘doesn’t go bad.’” He thinks that these attributes will help the technology spread in the industry.

At press time, Briggs & Stratton was offering the propane engine to any commercial lawn mower manufacturer, but those mower companies interested in using the engine are responsible for arranging and equipping their mowers with the necessary fuel delivery system (a product designed to deliver the propane from the propane cylinders, through a regulator and to the engine). The Ferris mower currently on the market uses a system produced by Onyx Environmental Solutions.

Patrick White is a freelance writer and editor who is always on the lookout for interesting and unusual stories.