Since 2000, the U.S. Environmental Protection Agency (EPA) has required diesel engine suppliers to reduce exhaust emissions on new engines that are manufactured for off-road use products in the U.S.
The EPA Tier 4i (Interim) emissions standards were effective until the end 2012, after which the Tier 4 Final went into effect. The EPA determined that any diesel engine manufactured after January 1, 2013 for use in an off-road product sold within the U.S. is required to meet the tighter EPA Tier 4 Final compliance standards. The EPA has provisions for some flexibility in completing the transition process.
One controversial requirement was the primary addition to the exhaust system with Diesel Exhaust Fluid (DEF). This is a mixture of pure water and Urea. When it is sprayed into the exhaust a chemical reaction occurs converting the exhaust to nitrogen and water vapor. The engine system needs to run hot to completely burn the fuel for the DEF system to work. If it is not running hot enough, diesel particulates collect in an exhaust filter, causing back pressure on the engine.
New pump stations must be built with Tier 4 engines. However, existing applications can continue using Tier 3 engines that meet some standards. MWI Pumps expert Joe Hathcock says there are many advantages to rebuilding existing Tier 3 engines rather than replacing them with a new Tier 4 engine.
Here are 7 reasons why it is a good idea to rebuild a Tier 3 engine rather than purchase a new Tier 4 engine.
- Tier 4 engines are more expensive. Purchasing a Tier 4 engine compared with rebuilding a Tier 3 engine requires about a 60% increase in cost. In addition, many other components are required, such as DEF fuel and a particulate filter that when clogged can shut down the engine.
- A Tier 4 upgrade may require a pump station modification. In most cases, the larger Tier 4 engines will require a larger platform, which also adds to the time and expense required to upgrade.
- Tier 3 engines do not require DEF fluid. Diesel exhaust fluid (DEF; also known as AUS 32 and marketed as AdBlue) is a liquid used to reduce the amount of air pollution created by a diesel engine. Equipment manufacturers are using selective catalytic reduction (SCR) to meet Tier 4 final emission standards. This technology injects DEF into the diesel engine exhaust system to achieve the necessary emission reduction by breaking down particulate matter and nitrogen oxide.
The good news is that DEF is nontoxic, nonpolluting, nonflammable, nonhazardous, stable, and colorless. The downside is that because DEF is nitrogen-based, it is corrosive to most metals and coatings. In addition, DEF is more susceptible to contamination than other fluids.
Tier 3 engines have no DPF filters. DPF (diesel particulate filter) is the technology that incorporates the high-tech filtering/regen processes to remove most solid carbon-based emissions from fuel exhaust. These Tier 4 filters can get clogged and must be removed to be cleaned, which creates more expense and more downtime.
Tier 3 engines do not have as many sensors that can malfunction or break. One major component required to meet Tier 4 standards is a sophisticated engine control system. This control system is housed in the engine control unit (ECU) and manages dozens of operating and environmental conditions in order to optimize horsepower, torque, and responses to changes in load. It allows the engine to maintain combustion efficiency over a broad range of operating conditions and minimize emissions in the exhaust. All engine parameters are communicated from this control system including pressure, temperature, regeneration requirements, and engine faults.
But according to Hathcock, there are more disadvantages than advantages to having these sensors. The Tier 4 engine sensors tell the engine when to perform a regen, the self-cleaning process. When the diesel exhaust sprays into the engine and burns off, the sensors must all be good. If one of them goes bad, the system goes into “limp mode”, and it will only operate at 20%, he explained. When this happens, the regen must be forced manually. This can cause significant downtime. The Tier 3 engines do not have these sensors because they don’t use DPF and therefore don’t need them because they are not burning anything off.
Tier 4 engines could require downtime for the regen process. The regen process is a costly self-cleaning of the system and exhaust filter. The temperature must be at a certain level to burn off the DEF liquid and send it out in the exhaust.
Tier 3 engines can operate with a wider range of loads. A Tier 3 engine can idle for hours or it can run at high speeds. A Tier 4 engine must run consistently at a high rpm—generally a minimum of 1600 rpm—which is not the most efficient speed for every application. Hathcock said it is an advantage that the Tier 3 engine can run efficiently at a variety of speeds.
The process in rebuilding a Tier 3 engine is not complicated, Hathcock said. It requires taking it out of operation, stripping it down, cleaning it thoroughly, and rebuilding it with new parts. Hathcock recommends using the original equipment manufacturer’s replacement parts and says the process can be accomplished effectively in a few weeks. This can include replacing liners, pistons, cooling injection pumps, and other parts.
Hathcock said it is time to look at rebuilding the Tier 3 engine when the efficiency begins to reduce. However, when done correctly, the properly rebuilt Tier 3 engine can last from 5 to 10 more years, depending on the frequency of use and considering that regular preventive maintenance is performed.
If your engine needs repair, or if you are considering rebuilding a Tier 3 engine, contact MWI Repair at (772) 770-0004 or fill out a contact form to discuss all maintenance and service options.