The new CAT D7E engine and drive system changes the way we look at power systems for construction equipment. Lambrecht Construction Co., Joilet, Ill., tries it out on their O'Hare Field construction project.
CATERPILLAR The new CAT D7E engine and drive system changes the way we look at power systems for construction equipment. Lambrecht Construction Co., Joilet, Ill., tries it out on their O'Hare Field construction project.

Contractors are concerned about equipment operating costs—fuel, maintenance, tool efficiency (unit of work achieved per unit of time), and the useful life of the equipment.

Given the rising cost of fuel, contractors may put fuel efficiency near the top of this list, especially for equipment with large engines. Engine manufacturers strive to accommodate these fuel economy needs, but their current goals focus on limiting exhaust pollutants. Managing nitrogen oxide (NOx) compounds, hydrocarbons, particulate matter, and carbon monoxide (CO) emissions from all nonroad engines (gasoline and diesel) is mandated by the Environmental Protection Agency (EPA) and can happen at the expense of fuel efficiency.

EPA requirements

Before the EPA began regulating engine exhaust pollutants, manufacturers focused more on engine efficiency—running equipment longer on less fuel. But growing concerns about air pollution moved the EPA to develop emission regulations. The regulations relate to engine size and type of fuel, and establish timelines for compliance. Joe Mastanduno, product marketing manager for the engines and drive-train division at John Deere, Moline, Ill., says much of the emphasis for engine manufacturers currently is focused on meeting these emission standards.

Since 2006, Tier 3 regulations have been in place. Tier 4 emission standards phase in over several years, starting with diesel engines below 25 hp, which took effect in 2008; Tier 4 requirements for gasoline and diesel engines above 75 hp and phase in between 2011 and 2014.

Even with these stringent regulations, engine manufacturers expect further reduction in exhaust pollutants. Bill Gearhart, construction division marketing and production manager for Yanmar, Adairsville, Ga., says this resulted when manufacturers made it clear they would have trouble economically reaching Tier 4 requirements. J.J. Zeilstra, emissions standards engineer for Kubota Engine America, Lincolnshire, Ill., adds that Tier 4 provides manufacturers a phase-in option to introduce new NOx-reducing technology.

Engine manufacturers

Equipment used by concrete contractors is powered by engines ranging from small two-cycle gasoline engines to 100-hp units that use gasoline-oil mixtures, gasoline, or diesel fuel. Low horsepower engines from 2½ to 36 hp tend to use gasoline, while larger engines generally take diesel.

Manufacturers want simple engine designs that provide good fuel efficiency, low exhaust emissions, and rugged durability. But as the industry moves toward Tier 4 requirements, these characteristics become more difficult to meet and the focus changes to satisfying EPA standards. Tier 3 and 4 regulations are most restrictive on higher horsepower engines because they can sustain the cost for reduced-emission technology and emit a higher quantity of emissions by volume. Here's what some companies are doing to control emissions.

Gasoline engines. Mark Johansen, a senior product manager for Kohler Engines, Kohler, Wis., says developed closed-loop fuel injection technology for all their commercial engine models (19 to 40 hp) will be completed by March 2010. Computer chips will monitor exhaust components, including unburnt fuel, NOx, and CO, and adjust spark timing and fuel mixture accordingly. He says this increases fuel efficiency by 15% to 25%. They predict fuel savings will pay for the increased engine prices in less than 18 months of use.

Scott Conner, an assistant vice president for the Honda Engine Co., Alpharetta, Ga., says his company's goal is to produce more power per cubic centimeter of piston displacement, reduce fuel consumption by 15% to 25%, and reduce exhaust emissions by 30%. Because Honda also manufactures cars, there are cooperative efforts between divisions to redesign combustion chambers and pistons, reduce emissions, and accomplish efficiency goals.

All Briggs & Stratton engines are gasoline models ranging in size from 2½ to 36 hp. Dan Roche, a marketing manager for Briggs & Stratton, Wauwatosa, Wis., explains the company's goal is to keep engine designs simple and practical, focusing on air-cooling systems and rugged durability. One example of practical technology is the low-rpm Vanguard v-twins that uses large displacement and high torque to complete the same amount of work as a smaller engine at a higher rpm.

Diesel engines. Diesel engine manufacturers are looking for inexpensive solutions, which are possible for Tier 4 Intermediate engines but not when Tier 4 regulations become effective. Zeilstra says a problem that arises when you reduce NOx gases by retarding engine timing is an increase in the amount of particulate. If you advance timing, you can limit particulate but that will increase NOx. So manufacturers choose which emission to control.

Gearhart says exhaust gas recirculation also addresses the problem of NOx. Higher combustion temperatures create more NOx and less particulate so recirculating some cooled exhaust gas through the combustion chamber, temperatures are reduced and the amount of oxygen is limited—more unused oxygen, less NOx.

Mastanduno says yet another way to manage NOx emissions is with variable geometry turbochargers (VGT). Deere includes VGT on its engines to manage the amount of oxygen that initially enters the cylinder. He says that by 2011, they also will include heavy particulate filters to control the particulate side of the emissions equation.

Some diesel manufacturers are using common rail fuel systems to electronically meter fuel into combustion chambers in just the precise amount at just the right time. Common rail injection is much more accurate than the mechanical injector pump systems. By replacing injector pumps with electronic meters, exhaust gases can be monitored to make fuel adjustments similar to gasoline engine technology.