Bobcat’s New Diesel Engines Without DPF and DEF Spark Debate

[MikePhua]

Bobcat’s Engine Shift and Emissions Strategy
Bobcat, a brand long associated with compact equipment innovation, made a bold move in the mid-2010s by introducing its own branded diesel engines in select skid steer models like the S630 and S650. These engines were designed to meet Tier 4 emissions standards without using a Diesel Particulate Filter (DPF) or Diesel Exhaust Fluid (DEF). Instead, they relied on a combination of Cooled Exhaust Gas Recirculation (CEGR) and Diesel Oxidation Catalyst (DOC) technologies.
This shift marked a departure from Bobcat’s previous reliance on Kubota and Doosan engines. While Kubota had a proven track record in compact equipment, Bobcat’s new engine design raised questions about long-term reliability, cold weather performance, and resale value.
Understanding Emissions Technologies in the 50–75 HP Range
Engines in the 50–75 horsepower category fall into a regulatory gray zone. Manufacturers can meet emissions targets using CEGR and DOC without resorting to DPF or SCR (Selective Catalytic Reduction). Bobcat’s approach avoids the need for DEF, a urea-based fluid used in SCR systems to reduce nitrogen oxides (NOx).
Key technologies used in this range include:

• CEGR: Cooled exhaust gases are recirculated to lower combustion temperatures and reduce NOx
  
• DOC: A flow-through catalyst that oxidizes hydrocarbons and carbon monoxide
  
• HPCR: High Pressure Common Rail fuel injection for precise atomization and multiple injection events
  

By omitting DPF and DEF, Bobcat simplified maintenance and reduced operating costs. However, this also meant the engine had to run hotter to reduce particulate matter in-cylinder, which raised concerns about durability and thermal stress.
Cold Weather Performance and Regional Impact
Operators in northern climates reported issues with cold starts and sluggish performance during winter. While these problems were less relevant in southern regions, they still influenced resale value and fleet decisions. Machines that struggle in cold weather are harder to sell in northern markets, even if they perform well elsewhere.
One technician in Wisconsin noted that fuel filter seating and fuel quality were common culprits behind cold weather faults. Low rail pressure and suction leaks caused by improperly installed filters were more frequent than actual engine failures.
Comparing Bobcat’s New Engine to Kubota and Doosan
Bobcat’s new engine was often mistaken for a completely in-house design. In reality, it was part of the Doosan engine family, which had already seen service in forklifts and air compressors. While these engines had a decent reliability record in industrial applications, their performance in skid steers—subjected to constant hydraulic load and variable terrain—was still being evaluated.
Kubota engines, by contrast, had a field population in the hundreds of thousands and were widely trusted. The switch to Doosan-based engines introduced uncertainty, especially for buyers who valued proven longevity over emissions simplicity.
DPF Myths and Real-World Regeneration Behavior
Many operators feared DPF systems due to early failures and regeneration confusion. In reality, modern DPFs perform passive regeneration during normal operation and active regeneration only when needed. On machines like the CAT 262D, the process is largely automatic. Indicators may prompt the operator to maintain throttle or idle, but the system rarely interrupts work.
Stages of DPF regeneration:

• Passive: Occurs during high-load operation, no operator input
  
• Active: Triggered when soot load increases, may require throttle or idle time
  
• Forced: Requires technician intervention if previous stages are ignored
  

The cost of DPF maintenance has dropped significantly due to widespread adoption in the trucking industry. Cleaning services are common, and most filters last thousands of hours before requiring attention.
Cab Design and Operator Comfort in CAT vs Bobcat
CAT’s D-series skid steers introduced a sealed, one-piece cab with integrated HVAC systems. This design improved pressurization, reduced noise, and simplified maintenance. The HVAC components were mounted directly to the cab, eliminating ducting issues during cab lifts.
Bobcat’s cab remained more modular, with easier ingress and egress due to lower thresholds and wider door openings. However, the CAT cab offered superior insulation, quieter operation, and better visibility through its backup camera system.
Comfort features comparison:

• CAT: Air ride seat, sealed cab, Bluetooth radio, flat floor
  
• Bobcat: Easier entry, simpler door removal, slightly more hydraulic power
  

Operators noted that CAT’s cab was quieter and more refined, while Bobcat’s layout was more utilitarian but effective.
Hydraulic Performance and Pump Design
Bobcat’s standard hydraulic flow was slightly higher than CAT’s, which appealed to users running demanding attachments like brush cutters or augers. However, the type of pump used also mattered. Gear pumps are less efficient than piston pumps, which offer better responsiveness and durability under load.
Hydraulic considerations:

• Flow rate (GPM) affects attachment speed
  
• Pressure (PSI) determines breakout force
  
• Pump type influences efficiency and heat generation
  

CAT’s piston pumps delivered smoother control, while Bobcat’s gear pumps were simpler and easier to service.
Final Thoughts on Purchase Decisions
Choosing between Bobcat and CAT often came down to dealer support, cab comfort, and hydraulic needs. While Bobcat’s engine design offered simplicity and lower maintenance, its unproven track record and cold weather quirks gave some buyers pause. CAT’s DPF-equipped machines were more complex but had matured into reliable platforms with strong resale value.
Operators were advised to:

• Demo both machines under real conditions
  
• Evaluate dealer proximity and service reputation
  
• Consider long-term fuel and maintenance costs
  
• Factor in resale value based on regional climate
  

In the end, the best machine was the one that fit the operator’s workflow, terrain, and support network—not just the emissions label on the engine.