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    Credit: 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.

In other words, most of your rolling stock.


The final set of emissions targets is split into two parts:

  • Tier 4A (Tier 4 Interim, Interim Tier 4, and iT4)
    • 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)
    • 90% less NOx than Tier 3
    • 2015-and-after model years

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 10% to 20% more expensive than iT4.

Upgrade, replace, or wait it out?

Federal law allows Tier 3 owners to use the equipment until the end of its expected service life. Therefore, it’s possible, but not necessary, to upgrade pre-iT4 engines unless your state requires it.

EPA’s Engine Flexibility Program allows equipment manufacturers to transition into producing iT4-compliant products but restricts the number of each “flex engine” backhoe, skid-steer loader, and excavator model they can manufacture annually. Non-government owners buying used equipment should be aware that future construction projects and bids might consider the ages and/or 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. On-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, fluids as directed by the engine and equipment manufactures. Fleet superintendents and 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 vijayakumar.palanisamy@us.atlascopco.com. Visit www.atlascopco.us. This story originally appeared in the 2013 Public Works Manual.


A cheat sheet for Tier 4 acronyms

Selective catalytic reduction (SCR): A means of converting nitrogen oxides, also referred to as NOx with the aid of a catalyst into diatomic nitrogen, N2, and water, H2O. A gaseous reductant, typically anhydrous ammonia, aqueous ammonia or urea, is added to a stream of flue or exhaust gas and is absorbed onto a catalyst. Carbon dioxide, CO2 is a reaction product when urea is used as the reductant.

Diesel particulate filter (DPF): A diesel particulate filter (or DPF) is a device designed to remove diesel particulate matter or soot from the exhaust gas of a diesel engine. Wall-flow diesel particulate filters usually remove 85% or more of the soot, and under certain conditions can attain soot removal efficiencies of close to 100%.

Variable Geometry Turbo chargers (VGT): A family of turbochargers, usually designed to allow the effective aspect ratio (A:R) of the turbo to be altered as conditions change.

Diesel Oxidation catalysts (DOC): Catalytic converters designed specifically for diesel-powered engines and equipment. DOCs reduce carbon monoxide (CO) and hydrocarbons (HC) including the soluble organic fraction (SOF) of diesel particulate matter (DPM).

ULSD fuel: ultra-low sulfur diesel fuel.

NOx: A generic term for mono-nitrogen oxides nitric oxide (NO) and nitrogen dioxide (NO2).