To comply with the U.S. Environmental Protection Agency’s Tier 4 Interim/European Union Stage IIIB emissions
standards that take effect in 2011, off-highway mid-range diesels must have particulate matter reduced by 90% and
NOx by 45% from current levels.

Although the Tier 4i deadlines are more than 2-1/2 years away, engine builders have been drawing and updating their emissions technology roadmaps since 1996, when the EPA’s Tier 1 rules went into effect. Several major engine suppliers, including Cummins, Caterpillar, MTU Detroit Diesel, Deere and Fiat Power Systems, used the recently held CONEXPOCONAGG trade show in Las Vegas (See Equipment Gallery, p. 90) as a platform to present their strategies for meeting the Tier 4i standards in their lower- and midrangehorsepower products.

Cummins, for example, announced that its Heavy-Duty QSX engine will be available with a fully integrated intake-to-exhaust scheme to meet Tier 4i regulations. The Tier 4 QSX increases displacement to 16 liters and incorporates a high-pressure common rail fuel system to enhance power output and engine response.

New technology brings a significant increase in QSX power output with an unrestricted top rating of 650 hp (485 kW) compared with 600 hp (447 kW) for the current Tier 3 QSX. Ratings will extend down to 400 hp (298 kW) to cover a range of applications. Peak torque is increased by 12% to 2,150 lb-ft (2.915 Nm) with faster torque delivery available across the engine rpm range.

“The next-generation Tier 4 QSX goes beyond meeting very low emissions levels to also offer higher levels of heavy-duty productivity than the Tier 3 QSX,” said Ric Kleine, vice president, Cummins Off- Highway Business. “We have been able to increase engine power and improve engine response for Tier 4 by increasing displacement and incorporating technologies such as Cummins’ XPI High Pressure Common Rail fuel system, a Variable Geometry Turbocharger and the new Direct Flow air filtration system. These subsystems are designed to offer an equivalent level of dependability to match that of the proven Heavy-Duty QSX base engine platform.

“While cooled EGR is primarily employed to reduce NOx emissions, we can also utilize this process to influence the combustion formula and realize fuel efficiency improvements. This will achieve up to 5% higher fuel efficiency for the Tier 4 QSX compared to Tier 3, depending on rating and duty cycle,” said Kleine.

Cummins XPI fuel system enables multiple injection events with very high fuel injection pressure across all engine rpm speeds to enable both cleaner combustion and improved engine response. The XPI fuel system is complemented by a Cummins Variable Geometry Turbocharger with a sliding-nozzle design. The nozzle continuously varies the airflow boost to match engine rpm and load demands.

According to the company, a particulate filter replaces the muffler in the exhaust stream and offers equivalent noise reduction qualities. The filter is strengthened against shock loads and vibration to meet severe off-highway operating conditions. Particulate matter collects on the filter and is gradually oxidized by catalytic passive regeneration. With some duty cycles, PM accumulation rate may eventually exceed oxidation rate, and a short active regeneration is initiated by the engine electronic control module utilizing the XPI fuel system and Variable Geometry Turbocharger.

“Reducing Tier 4 installation complexity for the equipment manufacturer has been a key aim of our QSX development program and we have been focused on keeping the engine and particulate filter envelope as space efficient as possible,” said Susan Harrison, executive director, Cummins Industrial Engineering.

Cummins has significantly increased the power of its Tier
4-compliant QSX engine, with an unrestricted top rating of
650 hp (485 kW) compared with 600 hp (447 kW) for the
Tier 3 QSX.

The QSX is available with the new Cummins Direct Flow air filtration system by Fleetguard, developed for Tier 4 applications. Direct Flow is claimed to offer a 35% smaller installation profile than typical Tier 3 air filtration systems while maintaining the same filtration efficiency. This is accomplished by creating a direct-flow path through the filter media which is packaged in a rectangular configuration rather than a conventional cylindrical shape. The Direct Flow housing includes a sensor to monitor temperature and pressure which sends data to the engine electronic control module to ensure optimum airflow operation.

MTU Detroit Diesel Goes with SCR
Contrary to both Cummins and Cat, Tognum’s MTU Detroit Diesel subsidiary plans to use selective catalytic reduction (SCR) and claims a high level of confidence in the technology. The company displayed at CONEXPO a Tier 4i-compliant Series 900 engine that uses SCR technology and stated that its Series 900 and Series 500 engine families were ideal candidates for the use of SCR to meet upcoming Tier 4i emissions regulations. “These engines have established themselves as the premier engines in their power class,” said Scott Jenkins, director of C&I Sales for MTU’s North American division, MTU Detroit Diesel. “And they have proven to perform just as well with SCR.”

Emissions reduction often works in opposition, explained Gerhard Kramer, director, Industrial Application Center for MTU. For example, reducing particulate matter often increases the output of oxides of nitrogen and vice-versa. “As designed, the Series 900 and Series 500 engines exhibit low particulate matter emissions,” said Kramer. “To comply with NOx limiting values, an SCR system is added.”

An SCR system works by injecting urea into the exhaust stream where it reacts with nitrous oxides to produce nitrogen and water. This reaction takes place when the urea and exhaust gases pass over a catalyst material in the SCR unit. Urea consumption varies with duty cycle and other factors but is not expected to exceed 5% of fuel consumption. As a rule of thumb, fuel consumption compared with Tier 3 engines is reduced by a similar amount, so that total consumption of liquids remains the same.

The SCR system itself consists of engine-mounted hardware, urea lines, electrical wiring and a catalyst unit somewhat larger than a muffler. The catalyst unit is used instead of the standard muffler. According to the company, service trucks can re-supply off-highway equipment with urea at the same time they refuel the equipment.

“Other emissions reduction technologies have merit and MTU has experience with all of them,” said Jenkins. “Our philosophy is to match the best technology to the needs of the specific engine, and in this case SCR was by far the best choice. We wanted to take these proven engine families with stateof- the-art designs, and bring them into compliance with the next round of emissions standards without compromising the benefits the engines. SCR allowed us to do that optimally by adapting the existing on-highway technology for industrial use.”

Inline four- and six-cylinder Series 900 engines have ratings from 120 to 322 bhp (90 to 240 kW), while V-configuration sixand eight-cylinder Series 500 engines cover ratings from 349 to 644 bhp (260 to 480 kW). The same SCR technology will also be used in the related 460 inline sixcylinder engine, which covers a power range from 348 to 483 bhp (260 to 360 kW).

MTU Detroit Diesel’s Series 60 engines are used widely in mining applications; for example, in Hitachi’s EH750-3 rigid body hauler as well as in Dux four-wheel-drive, articulated dump trucks used in underground mines. Their 12V2000 and 16V4000 engines, rated from 760 hp to 3,000 hp, respectively, power Hitachi’s larger haul trucks including the flagship EH5000ACII.

Cat Stays with ACERT, Adds Exhaust Aftertreatment
Caterpillar announced that its Tier 4i engine technology for construction and industrial mobile equipment engines, including those sold to industrial OEM customers, will continue to follow its ACERT technology path. Cat’s Tier 4 engine systems will be equipped with PM aftertreatment technology, including oxidation catalysts and diesel particulate filters with advanced regeneration systems that will optimize uptime, fuel efficiency and operator convenience. The engines will not use selective catalytic reduction (SCR) to meet Tier 4 Interim regulations.

Cat’s particulate filter system features a passive regeneration system to automatically remove particulate buildup. The filter requires no downtime to regenerate and no external heat source or fuel source. In January 2008, Cat reported that the system had earned Level 3 conditional verification for off-highway machines from the State of California Environmental Protection Agency Air Resources Board. The verification formally recognizes the Caterpillar passive filter system as effective in achieving at least an 85% reduction in particulate matter exhaust emissions. The system also meets the California 2009 regulation governing nitrogen dioxide emissions. Conditional verification is equivalent to verification, making the system legal for sale in California.

The verification covers wheeled machines with Tier 1, 2 and 3 engines in the 175 to 300 hp range. Caterpillar expects the verification to be extended to tracked machines and the horsepower range extended as more field test data are considered.

Deere’s Tier 4i Plan Adds New Technology to Tier 3 Platform
To achieve compliance with Tier 4i emissions regulations, John Deere Power Systems plans to start with its Tier 3 PowerTech Plus engine platform, add a diesel oxidation catalyst (DOC)/diesel particulate filter (DPF) unit for reducing particulates, and increase the percentage of cooled exhaust gas recirculation (EGR) for NOx control. Deere will not use SCR for interim Tier 4 compliance, claiming that its EGR and DOC/DPF technology path is more proven, simpler and less costly to operate.

PowerTech Plus engine models in the 130-kW (174-hp) and higher power class include the 6.8L, 9.0L and 13.5L in-line, six-cylinder engines, all of which feature a four-valve cylinder head, high-pressure fuel system, variable geometry turbocharger (VGT) and an air-to-air aftercooling system. For Tier 4i, the cylinder head, fuel system, EGR, VGT and air-to-air aftercooling systems will be updated but will be similar to Tier 3 configurations. The engine control unit (ECU), developed and manufactured by Phoenix International, a unit of John Deere's Intelligent Mobile Equipment Technologies, will be modified to provide twice the RAM, double the processing speed and four times the program memory of the previous version to handle requirements of added sensor and control logic.

Deere Power Systems’ Diesel Particulate Filter,
shown here in a cutaway view, will replace a vehicle’s muffler
in most applications.

Deere said it developed its DOC/DPF unit specifically to meet the demands of offhighway applications. The DOC component reduces carbon monoxide, hydrocarbons and some particulate matter. The downstream DPF traps and holds particulates remaining in the exhaust stream. Trapped particles are eventually incinerated within the DPF during regeneration. In most cases, the regeneration process will not have an impact on machine operation and will not be noticeable to the operator. Another benefit of the DOC/DPF is that it replaces the need for a muffler in most applications.

Tier 4i regulations require engine manufacturers to also consider crankcase emissions, which must either be managed via a crankcase filter or must be counted in the total engine emissions. The next generation of John Deere engines will be equipped with either a closed or open crankcase ventilation system (CCV/OCV) to manage these crankcase emissions.

John Deere claims to be the first engine manufacturer to widely commercialize cooled EGR and VGT technologies in offhighway applications, introducing them in 2005 with the start of Tier 3 regulations. According to the company, its Tier 3 engines and related technologies achieved record fuel economy gains over its Tier 2 models.

While conceding that SCR is effective, Deere noted that the technology requires that the vehicle or machine be fitted with a separate tank, a urea injection system and a tamper-proof diagnostic system. Since urea freezes, heating systems for the tank and delivery lines are required. In addition, urea is not conveniently available in most parts of the world at the present time, which creates access and storage concerns. Deere noted that SCR may be an appropriate technology for Final Tier 4/Stage IV regulations, when the technology is more developed for off-highway applications.

For Final Tier 4/Stage lV, Dr. Xinqun Gui, manager of engine technology for JDPS, said: “Technologies such as cooled EGR, VGT, DOC and DPF will likely be the foundation technologies for meeting those regulations that start in 2014. SCR may have a role. We are constantly evaluating emerging technologies for their effectiveness and for their ability to provide reliable and durable products in an off-highway setting. And as with engine configurations for previous emissions Tiers, we’ll continue to tailor our Final Tier 4 engine solutions to fit the variety of applications off-highway customers use them in.”

Fiat Powertrain Technologies’ F32 diesel.

FPT’s diesel product line extends from 20 to 1,800 hp with displacements ranging from 1,000 to 30,800 cc.

At CONEXPO, FPT NA exhibited its new F32 engine, one of the company’s F series models specifically for off-highway and stationary applications. Available in 74, 82 and 87 hp versions—rated at 2,500 rpm— the engines are four-cylinder in-line units with 3.2 L displacement. The new power units are compliant with EPA Tier 3/EU Stage 3A emission standards for off-highway applications.

Development of the new F series engine family was focused on a simple and compact design for easy installation and easy and low cost maintenance. The F32 features “one side service maintenance,” with the oil filter, fuel filter and oil level control on the same engine side. The engine is available with external cooled EGR or internal EGR, TC or TCA versions for the best trade-off between performance and cost effectiveness; the electrically controlled, cooled EGR, with its precise exhaust gas recirculation flow, enables lower emission on TC engines while the internal EGR guarantees cost effectiveness on TCA versions.