Rugged Gas Engines Deliver Same Performance as Diesel

Rugged Gas Engines Deliver Same Performance as Diesel
Rugged Gas Engines Deliver Same Performance as Diesel

As engineers, equipment manufacturers, managers, fleet owners, and end users wrestle with the complex after treatment often required on compact diesel engines, many are not aware of an innovative solution now entering the market.

The diesel engine industry faces major compliance and technical hurdles as potential Tier 5 legislation looms on the horizon.

Some engine companies are developing new diesel lines and after-treatment devices to meet the standards. However, these advancements often increase purchase costs and installation complexity. Other manufacturers are expanding their efforts by looking at alternatives to diesel and after-treatment devices.


Regulatory roadblocks
The force driving the hunt for alternative solutions to diesel engines is increasingly stringent diesel emission regulations. Engine companies employ the brightest engineers in the industry tasked with meeting those standards, and today, some find themselves with engines producing cleaner exhaust emissions than the air they take in.

Those ultra-clean engines need full-authority electronics, after-treatment devices, and low-sulfur diesel to function, sending manufacturing and purchasing costs for end users skyrocketing.

Some producers have managed to meet the Environmental Protection Agency (EPA) and California Air Resources Board (CARB) diesel emission regulations for engines with a power range below 75 hp by using common rail fuel systems, cooled exhaust gas recirculation (EGR), and a diesel oxidation catalyst (DOC). The DOC is particularly important in lifting equipment because the typical duty cycle of aerial work platforms includes extended periods of engine idling, which reduces exhaust gas velocity and temperature.

However, the easiest way to clean up diesel particulate emissions is to add a diesel particulate filter (DPF). These devices are effective, but have a downside: They require cleaning and eventual replacement. It is possible for applications with a 50% or more full-bore utilization cycle to create fast-flowing exhaust and enough heat to burn off captured diesel particles, but these applications may eventually lead to loss of end-user productivity.

For example, if a boom lift elevates a person into the air then idles for several hours while he or she is working, the DPF will likely plug up. The resulting filter cleaning takes time away from production.

For that reason, the passive, maintenance-free DOC has become the engine after treatment of choice. It uses precious metals to convert nitrous oxide and particulate matter into harmless exhaust gases. But like other diesel-based solutions, this one is also met with skepticism and could soon be extinct.


Growing health concerns
According to the EPA, diesel engines are one of several man-made sources that contribute to directly emitted particulate matter in the atmosphere. Research shows that those fine particles in the air may lead to health problems in humans and environmental impacts, such as ozone formation or acid rain. As a result, the EPA continues to toughen its regulations.
In some countries where consumers focus more on fuel costs and miles per gallon, the use of diesel-powered vehicles is becoming widespread. In Europe, more than 50% of all new cars now use diesel fuel, increasing the concentrations of nano particulates in the atmosphere. To fight the problem, the European Union is proposing Tier 5 diesel engine emission legislation that outlaws the use of DOCs and requires all industrial engine manufacturers to capture nano particles with a DPF.

After implementing Tier 4 regulations in the United States, the EPA and CARB will likely follow suit with requirements similar to the European Union’s proposals. Current estimates say Tier 5 legislation could come as early 2020, with little or no provision for engine flexibility programs.

That leaves manufacturers of cranes, forklifts, and access equipment with a potential dilemma: either accept the DPF filters and deal with the possible customer fallout from eventual product problems and loss of productivity, or search for alternatives to the diesel engine and DPF combination.

A gasoline solution
The impending legislation is pushing several engine manufacturers to action. Some are using much lower-powered diesel engines connected to electric motors or batteries, hoping the legislation and DPF requirements will not apply to engines with such low horsepower. This solution works for smaller powered machines, up to about 50 hp, but it does not address the higher-horsepower engines needed for larger equipment, and their accompanying high costs and packaging complexity.

Other engine makers are taking a more unique approach. Kubota, for example, is converting its diesel engine architecture to create a full line of spark-ignited engines that can be used with gasoline, propane, natural gas, or dual-fuel options. Those engines make up Kubota’s WG Series, now available in five models in sizes from 0.74L to 3.8L and 23.5 to 97.9 hp.

With the WG Series, Kubota is now the only engine manufacturer in the world that offers a full range of complementary compression-ignited/spark-ignited engines below 100 hp. It gives OEMs the option to use either diesel or gasoline without drastically re-engineering the installation envelope of the engine.

Kubota wanted to provide its customers with power solutions to meet all current and future legislation. Kubota’s product planning has enabled it to meet almost any customer requirement for performance, installation envelope, and fuel type.

To best decide between a compression-ignited or spark-ignited engine, customers should consider availability of fuel types, market acceptance of fuel types, local emission legislation, certifications, and registration, along with the machine’s operating environment, including factors like indoor or outdoor use and extreme weather.


Not adapted from autos
Although most gasoline engines on the market today are automotive based, Kubota’s WG engines are industrial based and designed to power heavy equipment, including the types used in the lifting industry. These spark-ignited engines can be employed wherever diesel equivalents are being used. They also provide commonality of installation, as well as similar levels of power and torque.

Because Kubota gaseous engines are created from diesel engine components, they inherit the same proven robustness, maintain the same interface and major service points, and feature heavy-duty drive gears. Automotive-based engines, on the other hand, typically use rubber drive belts, which are more prone to damage and possible engine failure.

The spark-ignited engines also operate at the same engine speeds as their diesel counterparts. Essentially, they should last equally as long because they can operate at lower RPMs, decreasing the wear rate of moving components.

In addition, Kubota’s range of large spark-ignited engines has gone through the same rigorous testing as the company’s equivalent diesel engines to assure that the new gasoline-powered models deliver the same reliability as the diesel models.

Because WG spark-ignited engines will perform the same tasks as compression-ignited models, OEMs and rental fleets in the lifting equipment and access industry can be confident that end users will not notice a difference in performance. Users will, however, happily notice that since spark-ignited engines don’t need a DPF filter or downtime for regeneration.


Accepted and cost effective
Instead of a DPF filter, Kubota’s spark-ignited engines use a maintenance-free, three-way catalyst similar to the catalytic converters now used in consumer-driven cars and trucks. In addition to being accepted by regulators, gasoline-based engines are also economical.

Typically, a gas engine costs less than an equivalent Tier 4 Final diesel engine. In addition to being lower in initial purchase cost, a gasoline engine runs on less-expensive fuel.

According to the New York Times, the oil industry is currently in its deepest downturn since the 1990s; oil prices have dropped more than 70% since June 2014. While motorists filling up their tanks will see the savings at the pump, pressures to create cost-effective options increase for companies relying on fuel to power their products. Gasoline is not only readily available, but it also consistently costs less at the pump than diesel.

Despite demanding legislation and higher costs, there will always be a need for diesel engine power. It has served the heavy construction equipment industry well for more than 100 years, and it has mobilized our populations to build the world’s future.

However, now may be the time to consider alternatives that offer the same performance and longevity as a diesel engine, but simply power productivity with a different fuel—gasoline.


Lift & Access is part of the Catalyst Communications Network publication family.