MOWER ENGINES: Power Forward

As landscape contractors become more sophisticated, so do mower engines. With more demand for power, longevity and fuel economy, mower engines are beginning to resemble something you’d see under the hood of a car rather than on a grass-cutting machine.

Contractors have several types of choices available when considering mower power, including liquid- or air-cooled, diesel or gas and, now, carbureted or fuel injected. One thing that hasn’t changed, though, is the desire for power and performance.

HORSEPOWER UP. Horsepower continues to increase, especially on air-cooled engines. Engines have risen in the last several years from an average of about 20 horsepower (hp) to 25 to 30 hp, according to Cam Litt, product manager of twin-cylinder engines, Kohler Co., Kohler, Wis.

The increased demand for horsepower may also result in higher prices. Retail price on mowers can increase between 3 and 5 percent for every unit of horsepower added, according to Kevin Lund, commercial mowing product manager, John Deere, Moline, Ill.

"The desire for more horsepower is a direct relation to industry demand for increased productivity," says John Chiera, national account manager for turf equipment, Briggs & Stratton Commercial Power, Milwaukee, Wis. "And to a commercial cutter, increased productivity is directly related to groundspeed. He wants to know, ‘How fast can I get this done?’"

Randy Lockyear, turf engines sales manager for Kawasaki Motors Corp., Grand Rapids, Mich., agrees that horsepower demands in the landscape industry are increasing. "If you spoke to someone 10 years ago and asked them if there was a need for 32 hp in this industry, you’d think not," Lockyear says. "Everyone wants to cut a little faster and get a little better cut, and you’ve got 72-inch decks that need quite a bit of power."

A machine’s horsepower often depends on the type of engine, how the mower’s being used and personal preference. Contractors who want to move from a 60-inch to a 72-inch deck may need that extra power to carry the extra weight, Litt notes. Additional horsepower also may be necessary if a contractor is installing attachments, such as a vacuum system.

During the early 1980s, landscape contractors used walk-behind mowers that ranged in size from 28- to 61-inch cutter decks with air-cooled engines that ranged between 8 and 12 hp, Chiera explains. Today, he says the average walk-behind mower has a 15- to 18-hp engine on it for greater productivity.

HadcoServices, Bartlesville, Okla., chooses horsepower based on several factors, including lawn type and frequency of use, says company President Wes Hadsell. "Typically, we don’t want more engine than we have to have to do the work we’re doing," Hadsell says. "If I’ve got a tractor pulling a brush hog and I’m going to be cutting only every two weeks or every month grass that’s 3-feet high, I need to buy a piece of equipment that has the horsepower to do that."

When Hadsell purchases hydrostatic mowers, typically he buys higher horsepower because the hydrostatic system robs the equipment of power, he says. On walk-behind mowers where there’s a pulley and a belt running just two wheels, he doesn’t need as much horsepower, Hadsell explains.

The lowest horsepower engine Hadsell purchases is a 4-hp engine for a walk-behind mower, he says. The highest is a 55-hp engine for an 11-foot-wide fairway tractor.

But higher horsepower isn’t always beneficial. Part of this reasoning is that horsepower is going to give you benefits in areas where you have a high requirement for torque or speed, Lund says. "It’s easy to say for a tractor that more the better," Lund explains. "But that’s not necessarily the case for a riding mower." More horsepower increases fuel consumption and generates more heat and noise, Lund points out.

Dowco Enterprises, Chesterfield, Mo., abandoned its higher-powered riding mowers for walk-behind models, says company President Maurice Dowell. "We got away from those types because of quality control," Dowell says. "We do a lot of high-end residential and if you put a big fire-breathing, water-cooled beast on their yard when it’s wet and you slide down a hill and tear it up, you’re not going to come back."

Dowco’s walk behinds are 17 hp compared to its 24-hp riding mowers, Dowell says. The company is considering moving up to higher-horsepower engines, but Dowell says price is always a factor. "We’re considering a 22 hp, but there’s a big tradeoff there," he explains. "You’re talking about adding about another $1,000 on that mower, and you have to ask yourself, ‘Am I going to get my bang for my buck?’"

FUEL SAVINGS. When considering new equipment, fuel economy is becoming more of a priority. Rising fuel costs have more manufacturers building mower engines with fuel injection systems rather than carburetors.

There’s no dispute that electronic fuel injection (EFI) systems can result in fuel savings, but how much is another matter. Litt estimates contractors saving up to 30 percent in fuel costs with EFI, but Lund estimates savings less than 5 percent.

"EFI is becoming more popular because it more efficiently uses your fuel, and it is a way to get your emissions down," Lund says. "As you get to bigger horsepower, it’s almost universal. You can realize some savings. But we haven’t seen the amount of fuel you’re going to save as a real purchase driver. People don’t necessarily buy EFI for fuel savings."

In addition to fuel savings and lower emissions, EFI can provide better throttle response and quicker starts in all types of weather conditions.

Electronic fuel injection systems can add $500 to $900 to the cost of an engine, Litt says. But usually contractors will realize a return on investment through fuel savings within one to two years, Litt adds.

Also, some manufacturers say demand for EFI is hindered because many mechanics aren’t trained to repair EFI systems.

Additionally, manufacturers are improving fuel efficiency through better debris management. Some newer engines feature high air flow blower housings that are integrated with a larger-phase modulated cooling fan and perforated steel rotating screen, which results in the engine running cooler and cleaner, according to Chiera. Some manufacturers have reduced engine temperature by as much as 30 degrees, which helps engines run more efficiently, he says.

Another trend is to move to diesel engines. Diesel power use tends to fluctuate depending on fuel prices, Chiera explains. Some landscape contractors are purchasing diesel-powered engines for greater fuel economy, horsepower and torque. Liquid-cooled diesel engines can improve fuel efficiency by 30 to 50 percent, Chiera says. Because diesel engines are typically liquid cooled, they cost substantially more than air-cooled gas engines.

"Customers need to weigh the upfront cost of a diesel-powered product vs. the long-term fuel economy," Chiera says. "The other advantage of a diesel-powered engine is its longevity. It will last thousands of hours – easily three times more than an air-cooled engine."

Hadsell buys diesel if the engine is bigger than 25 hp, he says. "I figure if the machine is going to wear out in three years, then you typically go with gas – if the machine is going to wear out in five years or more, you buy diesel because a well-maintained diesel will out last the machine they’re with," he says.

COOL RUNNINGS. Working in the summer heat can be grueling, especially for mower engines. That’s why cooling systems are one of the most critical features on a mower engine. Contractors and manufacturers continue to debate the merits of air-cooled vs. liquid-cooled engines. Each has its advantages and disadvantages.

Air-cooled engines are more popular with landscape contractors, mainly because of price. Chiera estimates that 80 percent of landscape contractors are purchasing air-cooled compared to 20 percent buying liquid-cooled engines. Liquid-cooled engines can be $300 to $400 more than air cooled, Litt says. Liquid-cooled engines are also heavier and because they contain radiators there are more parts to maintain.

But historically air-cooled engines don’t cool as well and have a shorter lifespan. Today, manufacturers are improving efficiency of air-cooled engines by redesigning the rotating screen and fan to better manage debris, Chiera says. Some fans now cut or shred debris and disperse it, so the material doesn’t get pulled inside the engine, Chiera explains.

"If you run an air-cooled engine at a low rpm or low load, it may last as long as a liquid-cooled at a high rpm, so the variables from one machine to another may be substantial enough to eliminate that benefit, but overall a liquid-cooled is going to last longer than an air-cooled," Lund says.

Larger displacement, higher-horsepower engines are typically liquid-cooled, Chiera explains. Liquid-cooled systems cool more consistently and reduce hot spots on the engine, which can cause gasket leaks, Lockyear adds. They also run quieter because the cylinders are encased in fluid, which absorbs noise and helps the engine run more efficiently resulting in increased fuel savings, he says.

Hadsell buys mowers equipped with liquid-cooled engines on everything except small push mowers, he says. "We’re in Oklahoma, and we’re pretty hot here in the summer, and I just feel like liquid-cooled machines will outperform and outlast an air-cooled machine," Hadsell explains.

But not everyone is convinced that cooling features or fuel efficiency drive mower sales these days. "To a customer, the type of engine doesn’t make a difference unless it doesn’t work," Lund says. "People may have preferences for liquid-cooled vs. air-cooled, but to a lot of our customers that’s a component. It’s like what kind of bearings they’ve got in their spindles. It doesn’t matter what they are as long as they don’t break."