Due to their compact nature, range of operating capacities and application versatility, skid-steer loaders pose a unique challenge when it comes to meeting Tier 4 Final emissions compliance. No one-size-fits-all solution exists. We are witnessing a variety of solutions — even within a given manufacturer’s line — as manufacturers select solutions they feel are in the best interest of their customers.
Emissions compliance has led to some of the most extensive changes to skid-steer loaders over the past decade. “Tier 4 Final compliance has been a major factor in the loader market in 2013,” says Jamie Wright, product manager, Terex Construction Americas. “One of the largest challenges manufacturers have with Tier 4 compliance is finding an engine manufacturer partner. Manufacturers need to pick a supplier that has a broad range of engine options ready for Tier 4 and that is able to engineer the engine options to fit into the loader’s engine compartment.”
Space is at a premium. “Tier 4 Final engines with diesel particulate filters (DPFs) require a lot more space because there needs to be room for the DPF to fit inside the engine compartment, as well as other added components that need to be incorporated into a loader to support Tier 4 Final regulations,” notes Wright.
Additional cooling capacity is also required. “Tier 4 engines require loaders to be engineered with larger coolers to disperse the heat produced by these engines,” says Wright.
When Terex developed its solution, it considered which approach best aligned with its customers’ needs and the way they used the machines. “The Tier 4 Final solution for Terex compact equipment came down to simple operation, low cost and no additives,” says Wright. “Terex has incorporated an EGR (exhaust gas recirculation) engine with a DPF exhaust system in our line of skid-steer loaders. EGR technology is well suited for lower horsepower engines operating in high duty applications.”
John Deere chose a similar approach. “Skid steers and compact track loaders less than 75 hp will incorporate EGR, a solution you are accustomed to in John Deere equipment, combined with exhaust aftertreatment,” says Sam Norwood, commercial work site product sales manager, John Deere Construction & Forestry. “Exhaust aftertreatment includes a DPF and diesel oxidation catalyst (DOC).
“Like our larger construction machines, cleaning to oxidize soot in the DPF takes place automatically and has no impact to machine operation under most operating conditions,” he adds. “This is a field-proven solution that has been used by John Deere in off-road applications for machines over 100 hp for several years. Machines greater than 75 hp will feature selective catalytic reduction (SCR).” NOx regulations for engines greater than 75 hp are more drastic than for those under 75 hp.
Understand Regen Cycles
Engines that use a DPF go through regeneration cycles to burn off the collected soot. “Heat in the exhaust system is required for regeneration to burn off the particulate matter trapped in the DPF,” says Wright. “All EGR engines with DPF exhaust systems capture soot until they fill up and create too much backpressure. At that point, the DPFs use one of two approaches to regenerate (clean) themselves: active or passive.”
Passive regeneration cycles occur continually when the exhaust temperatures are hot enough, and are transparent to the operator. No intervention or action is required. “During normal operation, the exhaust heat will naturally clean the [soot] buildup in the exhaust filter,” says Norwood.
“For machines operating in a high duty cycle environment, like skid-steer loaders, enough heat is generated to clear the DPF through passive regeneration, which does not impact machine operation,” says Wright.