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Posted: 05/16/2019

What does a “Tier 4 engine” mean?

Bobcat mechanic servicing Tier 4 engine.

The evolution of Tier 4 emission standards in the construction industry has been happening for years. But, how do Tier 4 emission standards, diesel engine technologies and treatment systems affect your equipment?

By taking the time to learn about Tier 4 emissions history and diesel engine technologies you can better understand the impact on your equipment and your bottom line.

History of EPA emission tiers

Most compact excavators, skid-steer loaders and compact track loaders are now Tier 4-compliant. They have gone through five different U.S. Environmental Protection Agency (EPA) emission tiers, ranging from Tiers 1 to 3, interim Tier 4 and then Tier 4, helping to lower harmful exhaust emissions and promote clean air.

The first set of EPA emission standards started in the late 1990s and continued throughout the early 2000s for all new nonroad diesel engines. Many manufacturers met this standard by featuring an improved engine combustion system to help reduce nitrogen oxides.

In 2004, a second level of emission standards was required. The major focus was on nitrogen oxides, hydrocarbons and particulate matter reductions. These standards improved fuel economy and lowered average engine operating temperatures with direct fuel injection systems.

Tier 3 standards, enforced from 2008 to 2011, typically affected machines greater than 75 horsepower and continued to reduce nitrogen oxide emissions. During this time, smaller horsepower machines (under 25 horsepower) went straight to Tier 4-compliant engines while 25- to 50- and some 50- to 74-horsepower engines moved to interim Tier 4-compliant diesel engines. In 2012, 75-horsepower machines and above made the move to interim Tier 4 emission standards. A year later, 25- to 74- horsepower machines were converted to Tier 4-compliant diesel engines.

Later, in 2015, the EPA mandated that all 75-horsepower or above nonroad machines reach Tier 4 compliance.

Tier 4 technologies

The path to achieve Tier 4 emission requirements wasn’t easy for nonroad equipment manufacturers. But, over time they were able to develop multiple technologies – ranging from mechanical fuel-injection systems to electronic injection systems – to meet strict EPA emission standards. Technologies such as an electronic control unit, a high-pressure common rail system, diesel oxidation catalysts and diesel particulate filters have been added to help reduce particulate matter, leading to cleaner exhaust.

In addition, many Tier 4-compliant machines have an additional system called selective catalytic reduction (SCR). SCR uses an ammonia- and water-based liquid called diesel exhaust fluid (DEF). Combining exhaust with DEF causes a chemical reaction that converts nitrogen oxides into harmless nitrogen and water vapor. Purity and concentration are critical with DEF, so work with your local dealer to better understand how to store and handle DEF.

Tier 4 fuel considerations

Improvements to Tier 4-compliant diesel engines help burn fuel cleaner and reduce air emissions. However, it’s important to learn how to best adjust to this significant fuel chemistry change – especially in relation to how water acts in fuel – in all seasons and temperatures.

Water can be introduced into fuel as early as the refinery stage and can continue to be present through the terminal, distributor and pump stages. During extremely cold weather conditions, water molecules can detach from diesel molecules, and since they are heavier than diesel molecules, they tend to settle at the bottom of diesel fuel tanks in a machine and bulk storage tanks. It can cause potential engine problems in equipment and lead to bacteria growth within the tanks. Today’s lower sulfur amounts in diesel fuel – which aids in reducing harmful sulfur oxides – can lead to what is called cold saturated fuel, which increases the tendency of fuel to gel and plug the fuel filter during cold weather conditions.

To identify minor issues before they become major repairs, follow these eight fuel best practices:

1.Test bulk fuel tanks every six months

2. Keep supply tank fuel filters clean

3. Fill machine tanks at the end of each workday

4. Use 2-micron fuel filters

5. Prepare for cold weather and remove trapped water from your machine’s fuel filter daily

6. Attend a fuel management clinic

7. Ask a fuel supplier to confirm the fuel’s cloud point

8. Identify the market’s high-quality fuel suppliers

Tier 4 maintenance

Improvements to Tier 4 engines means you need to stay on top of maintenance. Always follow the recommended maintenance schedule as listed in your Operation & Maintenance Manual for engine oil, filters and hydraulic filter changes to promote your machine’s long-term durability.

Although most equipment maintenance schedules have not changed in the move to Tier 4, recommended oils have changed to CJ4 engine oils which can be purchased from your local equipment dealer. These fluids are designed to work properly with aftertreatment systems while maintaining expected engine performance and service intervals. If you fill your Tier 4 engines with incorrect oil, it can cause costly damage to the machine’s emissions components. Those components can become plugged, corroded and inefficient.

To help keep maintenance to a minimum, some manufacturers now equip their machines with non-DPF engines. With non-DPF engines, you don’t have to worry about cleaning or replacing diesel particulate filters. Plus, the machine doesn’t have to burn extra fuel to heat the filter during the regeneration process. That means you can continue your operation without shutting down the machine on the jobsite.

By understanding the history of Tier 4 and the technologies needed to make the shift to Tier 4 emission standards, you can be better informed on how these technologies impact your equipment.