Understanding Emissions Regulations

The Environmental Protection Agency (EPA) emissions regulations have dominated the news lately, especially because Tier 3 standards for off-highway diesel engines started taking effect in January 2006. All of this can be very confusing to the end-user, but the whole concept can be boiled down into easily digestible bites. It isn't hard to explain what the regulations mean to you, the customer.

To understand the implications of Tier 3, it's important to know where the emissions-reduction push began. It all started with the 1990 Clean Air Act, when the EPA proposed a tiered emission-reduction plan for off-highway engines of all sizes. The EPA's designated Tiers indicate deadlines for engine manufacturers to adopt technologies that gradually lower engine emissions. The European Union (EU) later adopted its own emissions-reduction plan that is similar to the EPA's Tier system, but the EU refers to its schedule in Stages rather than Tiers.

Currently, the EPA regulates only 0.3 percent of an engine's total product of complete combustion. The rest (99.7 percent) of engine exhaust is made up of natural elements in the air such as nitrogen, oxygen and water vapor. The two main emissions that are regulated are oxides of nitrogen (NOx) and particulate matter (PM). As diesel engines move from Tier 1 to completing Tier 4 Final, emissions will be reduced to almost nothing. More specifically, NOx will be reduced by more than 90 percent, and PM will be reduced by more than 95 percent.


Let's look at a quick breakdown of the details. The Tier level's effective dates are as follows for engines 37 kW to 560 kW (50 hp to 750 hp):

  • Tier 1 spanned 1996 through 1999.
  • Tier 2 spanned 2001 through 2004.
  • Tier 3 spans 2006 through 2008.
  • Interim Tier 4 spans 2008 through 2012.
  • Final Tier 4 spans 2012 through 2015.

Each Tier consists of a “phasing in” of horsepower ranges. So, to use Tier 3 as an example:

  • 130 kW to 560 kW (175 hp to 750 hp) engines must be compliant with regulations by 2006.

  • 75 kW to 130 kW (100 hp to 175 hp) engine standards will take effect in 2007.

  • 37 kW to 75 kW (50 hp to 100 hp) will have to meet Tier 3 standards by 2008.

This means that, for the grounds maintenance industry, a 50-hp engine commonly used in a skid-steer loader or a mini excavator has to meet Tier 3 emissions by January 2008. Regulations for engines smaller than 50 hp skip Tier 3 altogether and go straight to Interim Tier 4. The same is true for engines larger than 750 hp. Check out www.dieselnet.com for a complete emissions schedule.

Another component of emissions regulations that might be confusing to end-users is the fact that engine manufacturers often promote their Tier-compliant engines ahead of the EPA schedule. That might mean you will see two announcements for the same engine: one for when the manufacturer announces it has demonstrated that its product is capable of meeting a specific Tier, and one for when the EPA officially certifies the engine according to the Tier timetable.

This all means that emissions compliance varies greatly within each engine manufacturer's line in order to satisfy the myriad needs of different end-users with diverse horsepower needs and engine requirements. Additionally, engine manufacturers have to comply with EPA and EU standards, as well as standards from countries around the world. This makes the diesel engine business even more complicated. Each engine manufacturer has to decide its strategy to satisfy the varying levels of emissions regulations worldwide.


But what does this mean for you, the customer? If you were already familiar with the EPA regulations and Tier schedules, you've probably heard the obvious environmental positives. Aside from working toward cleaner air, engines meeting emissions standards can also bring with them many end-user benefits.

While working to comply with Tier 3, some manufacturers have been able to improve engine performance and fuel economy, which are very tangible customer benefits, especially when most customers expect manufacturers to keep levels the same.

In general, a lot of misunderstanding and anxiety have surrounded the emissions issue, and addressing these concerns head-on should show the end-user why the EPA standards are good for everyone. For more information about the benefits of Tier 3 engines, see the “Clearing the Air” sidebar on page 24.

An important thing to remember is that most engine manufacturers can discuss Tier 3 — with certainty and in detail — regarding engines in the 175-hp to 750-hp range because those are the engines that had to meet regulations this year. However, design development and verification testing is a long, evolutionary process, and engine manufacturers are typically developing and testing more than one solution. As a result, final information on lower-horsepower Tier 3 engines with emissions deadlines in the future is less detailed, and the information is even less firm for Interim and Final Tier 4 solutions. That said, many of the technologies applied to engines 175 hp and above will be applied to Tier 3 engines less than 175 hp.


Unfortunately, the market is sometimes too focused on the complex nature of the EPA Tiers and effective regulation dates, and customers often engage in the negative discussion that commonly arises when equipment improvements are involved. But, in the end, it's critical to realize that the emissions regulations have a great deal to do with not only a better environment, but also the increased performance and improved fuel efficiency that these new engine technologies can possibly provide.

When you combine all of this with the environmental benefits, it's all significantly positive for this generation and generations to come.

Jennifer Oredson is a technical writer at Two Rivers Marketing (Des Moines, Iowa).



Q: I've heard that fuel consumption will be worse with Tier 3 engines. Is that true?

A: Many of the technologies available to meet Tier 3 increase fuel consumption, so it has been a real challenge for many manufacturers to meet their own Tier 2 standards, let alone improve on them. While several manufacturers were unable to meet their fuel economy levels from Tier 2, other manufacturers have been able to maintain Tier 2 fuel economy levels. However, a few manufacturers were able to improve their fuel economy over Tier 2.

Q: Is it true that cooling systems will have to be larger because Tier 3 engines have higher heat rejection?

A: All manufacturers have to deal with higher heat rejection for Tier 3. Depending on how well the OEMs manage their cooling systems, they might or might not have to increase the size of their cooling package.

Q: Will cooled EGR require low-sulfur on-highway diesel fuel?

A: Not all engine manufacturers use cooled EGR for their Tier 3 engines, but for those that do, diesel fuel recommendations generally remain unchanged, so on-highway fuel is not required. Most engines with cooled EGR technology are designed to operate with diesel fuels up to 5,000 ppm sulfur, which is the maximum amount allowed in the United States, Europe, Canada, Australia and New Zealand. Geographic areas that require Tier 3 engine platforms are also mandating the use of low-sulfur and ultra-low-sulfur fuels. As of January 2006, the most commonly available diesel fuel will be 500 ppm sulfur or less, and by October 2006, the most commonly available fuel will be 15 ppm sulfur.

Q: People are saying that new low-emissions engines compromise on performance to meet regulations. Will Tier 3 engines have lower power density?

A: From an industry-wide perspective, some manufacturers have decreased power density with their Tier 3 engines, and some have not. Some manufacturers offer different levels of technologies, some that have lower performance and some that have maintained or increased performance levels from their Tier 2 engines.

Q: Tier 3 engines sound so complicated. They must require more maintenance.

A: All engine manufacturers are going to offer extended oil-change intervals beyond the current Tier 2 recommendations. These intervals are made available through higher-grade oils, oil pans with greater capacities and oil filters with higher filtration capabilities.

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