MOWERS: Powerplant Possibilities

Richard Cafaro always tries to get the largest horsepower on an engine, whether it’s a walk-behind or zero-turn. But it’s not the engine’s most important attribute, says the president of LMS Co., of Allison Park, Pa. “I don’t know that you can ever have too much power on a mower,” he says. “When you look at the costs associated with upsizing the engine, having more horsepower costs little per dollar considering the overall investment.”

For Cafaro and contractors like him, serviceability, location, torque and makeup of key components are far more important factors in choosing an engine that suits their needs than horsepower alone. Adding horsepower to zip around a property just won’t cut it. “You have to be careful weighing out speed as part of the equation,” Cafaro says. “While you’d like to get the work done as quickly as possible, the property still has to look great when you’re finished.”
 
Contractors spend plenty of money on new engines, Lawn & Landscape’s 2006 State of the Industry research reveals. In the last 12 months, 12 percent of contractors bought new engines, while 8.8 percent plan to do so in the next 12 months. On average, contractors spend nearly $2,000 a year on engines. Increases in productivity, efficiency and quality are the challenges that will always be there, says Doug Page, director of marketing for Milwaukee-based Briggs & Stratton. “Let’s say I have a fleet of 10 mowers. Every year, those 10 mowers need to perform more than they did last year… and probably because my expenses may be going up my margins aren’t going up as fast,” Page says. “So the question is – ‘How can I do more with the same amount of machines and people?’”

THE HORSEPOWER RACE. “Higher horsepower engines themselves are not that important,” Page says. “They only become important in the mower manufacturer’s engineering and the engine’s engineering departments, where we make sure the engine, the deck size, machine size, cut quality – all those things are in balance, so when a dealer sells to a contractor, the contractor ultimately is more productive, regardless of machine size.”
 
Manufacturers are nevertheless involved in the “horsepower race,” says Rich Koehl, director of marketing and quality for Kohler, Wis.-based Kohler Engines. Manufacturers continue “trying to squeeze the most horsepower out of the smallest frame. People are trying to keep under that magic 1 liter,” Koehl says. “So you have frame sizes that go up to 999 cc’s.” The reason manufacturers stay below the magic 1 liter figure is there are additional regulatory compliances, Koehl says. “You have other emissions and regulatory aspects that come into play. Mainly, lots of government-driven emissions items.”
 
The best indicator for the type of engine required is dictated by the jobs the contractor needs to complete, Page says. “Regardless of engine size, it’s always a matter of keeping with what the customer is trying to accomplish,” he says. “Usually our customers are seeking more productivity, easier maintenance and the ability to have quality of cut in all conditions.”
 
Bigger isn’t always better, Page says. “Let’s say that same contractor has numerous, smaller residential customers,” he says. “Perhaps they need a more medium-size or smaller-size machine to get through gates, to get around the landscaping. At that point, the productivity isn’t in the bigger machine, the productivity could be in the smaller machine that’s more nimble, that’s able to get in and out of the yards.”
 
It’s always about matching the machine to the intended work and that would drive productivity, because sometimes a big machine doesn’t help if the physical property doesn’t lend itself to a big machine, Page says.

For zero-turns, the deck size will determine how big the engine needs to be, Koehl says. “On most of today’s mowers up to 60-inch decks, 30 horsepower and below winds up doing just fine,” he points out. “When you get into very wet and tall grass, you’re going to need more horsepower in order to get through it.”
 
And with walk-behinds, manufacturers have begun to measure work capacity in terms of torque, instead of horsepower. “When you look at torque, you want to look at peak torque, meaning what is the total out-torque you’re going to get from that engine with a muffler,” Koehl says. “The higher the torque, the higher and wetter grass you’ll be able to mow. A lot of people are going with gross torque measurements. When you look at gross torque, that’s what the engine has the capability of doing if it was a perfect world.”
 
Torque is a rotational force that can be illustrated with the common cordless drill. When these drills run into resistance during operation, they tend to twist the arm of the operator. How hard the person’s arm is twisted is the measure of torque. But an engine doesn’t need a lot of horsepower to reach a high measure of torque.
 
“You can have a very high horsepower and a very crappy torque engine,” Koehl says. “You can have a very low horsepower and a very good torque engine. The higher the torque, the better the grass will get cut. If I  move it through that grass without the blade losing speed, then I will cut that grass and it won’t kill the engine.

AIR-COOLED VS. LIQUID-COOLED. Whether a contractor wants an air-cooled engine or a liquid-cooled engine comes down to how long they intend to keep the engine and how much they’re prepared to spend. Air-cooled engines are cheaper and simpler to maintain than their liquid-cooled counterparts. “A liquid-cooled engine will run cooler than air-cooled, which means they’ll have longer engine life,” Page says. “A liquid-cooled engine requires a little more maintenance because it has a radiator, and it has coolant.”
 
A contractor can expect to pay 20 to 30 percent more on a mower featuring a liquid-cooled engine. Koehl says liquid-cooled engines are very durable, long-lasting, quieter and more efficient. “Liquid-cooled really becomes a question of – ‘Do I need the super-quietness of the engine, like my car engine?’” he says.
 
A contractor who intends to keep an engine running for three years, for example, may want an air-cooled design, Page says. “But let’s say you plan on keeping it five years,” he says. “Or let’s say you plan on cutting more acres per year, then you might want to consider liquid-cooled.”
 
Manufacturers have made strides in recent years that make air-cooled models attractive. They’re lightweight and have fewer moving parts to service. Some two cycles now meet stricter EPA and CARB Tier II emissions rules without the use of a catalytic converter, which adds weight and cost to the mower. “Air-cooled engines are very simple, easy to maintain. They will last a long time,” he says. “It depends on the contractor’s business plan.” Walk-behinds are the domain of air-cooled engines; when it comes to zero-turns, both air-cooled and liquid-cooled come into play. “On a walk-behind, you wouldn’t find liquid-cooled because of weight and size restrictions,” Page says.
 
The quietness many contractors sought in liquid-cooled engines is available on air-cooled models. “Air-cooled engines these days are very efficient,” he says. “The noise has come down; the amount of heat dissipation so that you can mow on even the hottest days, you’re going to be able to mow without much of a problem.”

FUEL-INJECTED VS. CARBURETOR. The fuel-management system is another important factor in choosing an engine. Cafaro is partial to fuel-injection. “The fuel injection on those engines is just tremendous. The power really stays,” he says. “Particularly if you’re mulching, having steady, consistent power is important and makes all the difference.”
 
As with liquid-cooled engines, contractors looking to buy a fuel-injected system will expect to pay more. “There’s usually some price premium associated with fuel injection, but it would be awfully difficult to say what percent because the fuel management systems are quite unique to each engine,” Page says. “The variance in price will depend on that particular engine.”
 
Even carburetors are becoming more efficient in the way they deliver fuel, Koehl says. But a carburetor will never be as efficient as an electronic fuel-injected engine. “You have electronic fuel-injected engines out there both open-loop and closed-loop,” he says. “What’s interesting about opened-loop systems, they’re nice systems and they do work slightly better than carburetors, but the true fuel efficiency savings only come when you run it in that perfect condition.”

In a closed-loop system, the fuel ratio is determined by both main engine sensors and exhaust sensors. In an open-loop system, only the main engine sensors dictate the fuel ratio. “One of the things contractors should be asking if they’re looking at fuel-injected systems is if it’s open-loop or closed-loop,” Koehl says. “If you’re truly looking for the perfect-running engine, closed-loop is the engine to look for.”
 
THINGS TO KEEP IN MIND. Regardless of the features a contractor deems important, as a practical matter, the engine should be as easy  to service. “Serviceability and location of the oil filters, as well as being able to access the air cleaner are critical,” Cafaro says. “A nice, large air cleaner is great.”
 
Contractors should choose engines with large oil filters and oil systems that are fully-pressurized. “The advantage is that you don’t have to worry about the incline that you’re mowing on or how your engine is positioned,” Koehl says. “Let’s say you do a lot of hill-mowing where you’re sideways. Some mowers are partially-pressured. If they run for an extended period, you can seize that engine, because depending upon where that oil gets sucked up from – whether it’s actually going to be there or not – a fully-pressured system says you should be able to make a 35-degree incline and run that way forever, without affecting your engine.”
 
Also, the larger the fuel filter the better the engine performance. “Fuel is probably one of the hardest things to control,” Koehl says. “The larger the fuel filter, the better chance you have of not getting crud from the gas into your engine and your carburetor.”
 
Contractors should consult their dealers in order to decide on the best engine. “The dealer will have a variety of equipment,” Page says. “The dealer can find out what profile of customer that contractor is trying to satisfy and what equipment will best match that contractor’s workload.”