The 2013 Dynapac F1000T track paver’s iT4 engine has a fuel injection system that reduces fuel consumption 5% compared to previous models.
Dynapac USA The 2013 Dynapac F1000T track paver’s iT4 engine has a fuel injection system that reduces fuel consumption 5% compared to previous models.

The U.S. has come a long way on its 17-year trek to cleaner air and has less than two years to go.

The 1996 implementation of EPA’s Tier 1 standards launched a schedule of progressively lower targets that ends with near-zero nitrous oxides (NOx) and particulate matter (PM) emissions for 2015 off-road diesel engines. This category, called nonroad mobile equipment engines, includes excavators and other construction equipment, airport ground service equipment, and utility equipment like generators, pumps, and compressors.

The final set of emissions targets has two parts:

  • Tier 4A (iT4) which requires 90% less PM and 50% less NOx than 2006 Tier 3 levels; applies to 2013 and 2014 model-year engines
  • Tier 4B (Final Tier 4) which requires 90% less NOx than Tier 3; applies to 2015-and-after model-year engines

Manufacturers have developed a host of technologies—direct-flow air cleaners, cooled-exhaust gas recirculation (CEGR), variable geometry turbochargers (VGT), diesel oxidation catalysts (DOC), and diesel particulate filters (DPF)—to meet these goals. That innovation has a price. iT4 engines are 5% to 15% more fuel-efficient but 10% to 40% more expensive than Tier 3 models; Tier 4B engines are 10% to 20% more expensive than iT4.

So the question becomes whether to upgrade, replace, or wait it out? Federal law allows owners of Tier 3 engines to use their equipment until the end of its expected service life.

EPA’s Engine Flexibility Program allows equipment manufacturers to transition into producing iT4-compliant products but restricts the number of “flex engines” they can manufacture annually. Non-government owners buying used equipment should be aware that future construction projects and bids might consider the ages and emission levels of their mixed fleet. So, prospective buyers should consider emissions performance of both new and existing equipment in trade and resale options.

Maintenance implications

A critical difference between Tier 3 and iT4 engines is that the latter require ultra-low sulfur diesel (ULSD) fuel and American Petroleum Institute CJ 4-certified, low-ash-content engine oil. Non-ULSD fuel can immediately damage an iT4 engine.

Beyond that, changes vary from one engine category to another.

Some iT4 engines that are less than 173 hp don’t have DPFs. Instead, the soot is continuously burned in the after-treatment system. Engines with DPF have additional indicators and a switch in the dashboard to alert operators to the regeneration cycle.

To learn if a piece of equipment is equipped with an iT4 engine, look for an ultra-low sulfur diesel fuel only decal in the fuel filling area. This is mandated on all iT4 machines regardless of power category.

Technicians are challenged to make sure they use the appropriate maintenance procedures and fluids as directed by the engine and equipment manufacturers. Fleet managers play a key role in training operators and maintenance crews on iT4 changes. New technologies may require formal classroom and on-the-job training.

Vijayakumar Palanisamy is product marketing manager of Atlas Copco Road Construction Equipment USA. E-mail; visit This article ran in our sister publication, Public Works, in Spring 2013.