Get FinancingTier 4 Final: What It Means For You
Whether you’ve been in the agriculture or construction industries for decades, or you’re a relative newcomer, you’ve no doubt seen the phrase “Tier 4 Final” used to describe all manner of new and used motorized machines available for sale on TruckPaper.com, TractorHouse.com, MachineryTrader.com, and CraneTrader.com, or for rental on RentalYard.com. There’s a good chance you already know that Tier 4 Final refers to emissions standards set by the U.S. Environmental Protection Agency. But in this post, we’ll briefly cover everything you need to know about these relatively recent regulations.
EPA Reins In Emissions
More than two decades ago, in an attempt to improve air quality, the EPA began to limit diesel exhaust emissions from newly manufactured non-road diesel engines, particularly those used in ag and construction. The target of the regulations include a sinister series of diesel combustion byproducts, including particulate matter (PM); nitrogen oxides (NOx), a precursor to atmospheric ozone); carbon monoxide (CO); and non-methane hydrocarbons (NMHC). The worst of these is PM, which consists of unburned fuel, oil, and sulfur compound-soaked specs of solid carbon; it’s the stuff in that noxious black smoke you traditionally associate with large diesel engines.
Starting in 1996, the EPA began pushing manufacturers to create engines that produce less and less of these harmful emissions, but because the technology of the time didn’t exist to feasibly meet the agency’s most ambitious goals, a tiered rollout was devised to afford engine and equipment manufacturers the time necessary to research and develop new techniques and technologies that would solve the hazardous exhaust problem.
Tiers Demystified
Depending on the rated horsepower output of the engine, the different Tiers require emissions to have successively less and less PM, NOx, CO, and NMHC particles.
To get an idea of the kinds of limits the EPA has called for, let’s take a look at an engine size that’s common to compact construction equipment, such as mini skid steers, compact track loaders, and mini excavators in the 50- to 99-horsepower class. Under Tier 1, these engines didn’t need to curb the production of CO, HC, NMHC, or PM, but they were limited to 9.2 grams of NOx per kilowatt hour (g/kWh). At Tier 2, these machines were further limited to 5.0 g/kWh of CO, 7.5 g/kWh of NMHC, and 0.4 g/kWh of particulate matter. At Tier 3, these machines could only generate two-thirds the amount of NMHC stipulated in Tier 2, down to 4.7 g/kWh. In 2013, a subset of these engines, rated from 50- to 74-horsepower, were further mandated to produce no more than 0.03 g/kWh of PM, a precipitous drop compared to the levels described in Tier 2.
Flux Fuel
I addition to regulating the emissions of non-road engines, the EPA has also mandated changes to the sulfur content of diesel fuel, though the regulations are much less complex. At Tier 1 through Tier 3, the sulfur content in non-road diesel fuels remains consistent with pre-Tier levels. According to the oil industry specification, diesel has an average in-use sulfur level of about 0.3%, or 3,000 parts per million.
Due to Tier 4’s tight emissions tolerances, a new Tier 4-compliant diesel needed to be developed. Ultra-low sulfur diesel fuel (ULSD) is limited to a mere 15 parts per million. On-highway vehicles have been using ULSD since 2006, but starting in 2011, the older high-sulfur fuel may be difficult to come by.
Emission Limiting Tech & Techniques
To become compliant with Tier 4 final regulations, it was going to take more than just some de-sulfured diesel and a few minor engine tweaks. The most common emissions controlling techniques also tend to have a detrimental effect on engine performance, including a diminished ability to rapidly produce enough power to lift and push heavy loads, called transient response, decreased performance in high altitude regions, and consuming more fuel to produce the same power compared to non-compliant engines.
There are a handful of add-ons that can enable an engine to meet the EPA’s requirements. For instance, a diesel particulate filter (DPF) is a component that’s frequently installed in the exhaust system to trap the harmful PM. As you can imagine, after running for months on end, these filters can get gummed up. To clean the filter, the vehicle can use a form of passive or active regeneration, which uses respectively warm and hot temperature exhaust cycles regularly to oxidize or burn off the accumulated carbon particles. Filters like these are typically referred to as an after-treatment technique.
Another of these techniques is called selective catalytic reduction (SCR), which slashes the amount of NOx that leaves the engine by squirting slight amounts of diesel exhaust fluid, a mix that often includes anhydrous ammonia, into the exhaust stream before it gets to the catalytic converter, resulting in harmless nitrogen and water. The diesel oxidation catalyst (DOC) is an after-treatment device that increases exhaust temperatures to convert CO to CO2, and hydrocarbons into CO2 and water.
There are also “in-cylinder” add-ons designed to reduce the production of pollutants during the combustion process. Some examples of these include combustion chamber modifications, variable-geometry turbocharging, and a high-pressure common-rail (HPCR) fuel system. Cooled exhaust gas recirculation (CEGR) is one common technique that redirects some of the exhaust gasses to the cylinders to reduce the availability of oxygen and consequently lower the combustion temperature. This results in significantly less NOx being generated.
Our Grass Is Greener
Due to the highly competitive nature of the construction equipment market, you didn’t have to be able to read the tea leaves to know that multiple exclusive technologies would be developed as a result of the Tier 4 Final compliance push. Here are a few.
John Deere’s PowerTech PSS engines rely on CEGR. The engine also features a 4-valve cylinder head that increases airflow for ample amounts of low-speed torque and excellent transient response. Deere also touts its PowerTech PSS engines for their diesel exhaust fluid consumption rate of 2% or less.
Caterpillar uses a variety of technologies to meet Tier 4 Final requirements and satisfy customer demands. The firm’s ACERT combustion technology relies on a fuel system that allows for multiple precisely timed injections during the combustion cycle, an advanced air system that cools the combustion chamber, and a wastegate turbocharger for delivering low-end response that customers expect from the equipment they buy.
Cummins’s Xtra-High Pressure Injection system has its own Tier 4 Final-compliant technology baked in. Cummins’s efforts aim to strike the perfect balance between in-cylinder and after-treatment techniques for controlling emissions without adversely affecting engine response and fuel efficiency.
Case Construction Equipment was an early champion of SCR due to the tendency of machines like wheel loaders and bulldozers to generate varying amounts of emissions that corresponded to irregular power demands.
The Tiers Are Here
In 2018, virtually any new or used non-road diesel engine you buy that has been manufactured in the past decade will be subject, to some extent, to the EPA’s Tier requirements. Our goal with this article is to answer any questions you might have had about what these requirements entail, or might mean for your business and future purchasing decisions. SIDEBAR
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EPA’s Tier Timeline
Here’s a simple timeline that describes the various deadlines manufacturers were required to meet to achieve compliance for each tier, depending on the engine’s horsepower. Note that the EPA created a separate—and less strict—tiered rollout scheme for emergency standby power generators, which we’ve excluded from the timeline below. For your reference, when looking at used equipment, you may encounter a machine rated as Tier 0; this effectively means that the engine was most likely manufactured before the EPA’s regulations went into effect, that it has no emission limiting capabilities, and this it is probably mechanically rather than electronically controlled.
Tier 1. These emissions standards went into effect between 1996 and 2000, starting with engines in the 175- to 749-horsepower classes. Smaller engines, such as those that produce less than 25 horsepower, were only required to meet the Tier 1 standard in 2000.
Tier 2. Engines that produce between 300 and 599 horsepower were the first to be Tier 2 certified, starting in 2001. The top end (750 horsepower) and bottom end (less than 25 horsepower) of the spectrum could take up to the beginning of 2005 to meet the EPA’s Tier 2 limits.
Tier 3. Only engines between 75-horsepower and 749-horsepower could gradually transition between the EPA’s Tier 2 and Tier 4 regulations, between 2006 and 2008. The Tier 3 Flexibility exception applies only to engines rated for between 600 and 749 horsepower, and it precludes them from having to meet the most dramatic emission cuts described in Tier 4.
Tier 4. The last series of emission standards created by the EPA are actually broken up into Tier 4 Interim, Tier 4 Interim Flexibility, and Tier 4 Final. Engines that produce 74-hoursepower or less needed to meet Tier 4 Interim limits by the beginning of 2008, while more powerful engines needed to meet those standards between 2011 and the start of 2012. Another exception, Tier 4 Interim Flexibility, let the 100- to 174-horsepower class engines dodge Tier 4 Final regulations indefinitely. Between 2014 and 2015, all engines not covered by one of the previously described exceptions needs to adhere to the EPA’s Tier 4 Final emissions regulations.
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