Tier 4 Interim/Stage IIIB emissions regulations beginning the first of next year for diesel engines 130 kW (174 hp) and above will require a 90% reduction in particulate matter (PM) and a 50% reduction in NOx from previous Tier 3/Stage IIIA requirements. The effective date for 56- to 130-kW (75- to 174-hp) engines is Jan. 1, 2012.
To meet the new regulations, John Deere Power Systems reinforced in an announcement at Bauma that it is starting off with the technologies it introduced on its PowerTech Plus Tier 3/Stage IIIA in-line, four- and six-cylinder engine platform, which represented one of the first uses of cooled exhaust gas recirculation (EGR) for NOx control in off-highway applications, with the addition of an aftertreatment system.
But will the T4I solution simply be a T3 engine with an exhaust filter tacked on? "At a high level, yes. But when you look a little deeper under the surface, no," Paul Holst, Product Manager at JDPS, told SOHE. "It's definitely a building block approach for us for Tier 4 over Tier 3. We adopted cooled EGR for Tier 3, high-pressure fuel systems, and electronic controls, and we’re building upon that by using next-gen technologies in those three areas, as well as exhaust aftertreatment."
Using the EGR system as an example, Holst says that "it is a smarter EGR system. It’s a closed-loop type operation, where it’s in constant adjustment with the ECU to give us the optimum EGR levels. We added a venturi in the EGR loop that accurately measures exhaust gas flow rates. And it’s taking that information back to the ECU. We also have a much more precise EGR valve that can precisely control the EGR flow. And the size of the EGR systems have grown because we are flowing higher EGR rates to bring the NOx down even further."
JDPS' aftertreatment system consists of a catalyzed exhaust filter that contains a diesel oxidation catalyst (DOC) upstream of a diesel particulate filter (DPF). The DOC component reduces carbon monoxide, hydrocarbons, and some PM. The PM that does get through it are stopped in the cordierite DPF.
"Periodically we have to regenerate depending on operating conditions and particle buildup in the DPF," said Holst. "Passive regeneration is our goal. It's hard to say or predict how often that would happen. It's very much application, ambient-condition, and operator dependent."
Engines from 56 to 129 kW (75 to 173 hp) will feature smaller exhaust filters that can be engine-mounted or remote-mounted for increased flexibility. Engines in that power range will use an in-cylinder dosing system, while engines 130 kW (174 hp) and above use an external dosing system.
"From a cost standpoint, it’s less costly to use in-cylinder dosing, and that’s why we have it on the less than 130 kW engines, which are much more price-sensitive," said Holst. "But there's also a technical reason. When you use in-cylinder dosing, you’re basically dumping, or injecting, raw fuel into a cool cylinder, and you can actually get some oil dilution out of that, with raw fuel getting past the rings and into the crankcase oil. So, from a reliability standpoint, we would be concerned about oil dilution above 130 kW."
Engines between 56 and 129 kW (75 and 173 hp) will be available in 4.5- and 6.8-L displacements and will be equipped with either a wastegate or variable geometry turbocharger (VGT) depending upon the size of the engine. Along with EGR, VGT technology was also introduced by JDPS in 2005 to meet T3. Since then, JDPS has accumulated significant operating hours with those technologies in off-highway applications and says it has established a proven field record of reliability.
JDPS expects to maintain fuel-economy levels similar to those achieved with its T3 engines, with the cooled EGR systems operating efficiently with ultralow-sulfur diesel as well as biodiesel blends.
While selective catalytic reduction (SCR) has made it onto more T4I engines than some may have thought three years ago, it did not make it with JDPS, which stands by its philosophy that the single-fluid approach of cooled EGR saves owners and operators the cost of diesel fuel plus the additional cost for diesel exhaust fluid required by SCR systems. That, and the fact its EGR and aftertreatment systems allow it to meet T4I, negated the introduction of SCR onto its engine.
Without committing to its T4 Final path, JDPS does concede that SCR may be an appropriate technology for the future, when the technology is more developed for off-highway applications.