Engine Swap from Komatsu S6D105-B1 to Cummins 5.9 6BT in PC200LC-3 Excavator

[MikePhua]

Introduction to the Engine Swap
Swapping an engine in heavy equipment like the Komatsu PC200LC-3 excavator is a significant undertaking that involves replacing the original Komatsu S6D105-B1 engine with a Cummins 5.9 6BT diesel engine. This process is often pursued to achieve better reliability, easier maintenance, and improved parts availability. The Komatsu S6D105-B1 is a Komatsu-designed inline six-cylinder diesel, while the Cummins 5.9 6BT is a popular industrial engine known for durability and widespread service support.
Background on the Engines

• Komatsu S6D105-B1: A six-cylinder inline diesel engine built specifically for Komatsu machines, providing about 140–150 HP. It features Komatsu’s own design standards, but replacement parts and service expertise may be limited depending on location.
  
• Cummins 5.9 6BT: A six-cylinder, 5.9-liter inline diesel engine known for ruggedness, often used in trucks, industrial applications, and retrofit projects. It produces roughly similar horsepower with a robust aftermarket and easy parts availability.
  

Reasons for the Engine Swap

• Parts Availability: Cummins engines enjoy a vast global network of parts suppliers and service centers, making maintenance more straightforward and cost-effective.
  
• Reliability and Durability: The Cummins 5.9 6BT is renowned for long service life and proven performance across various industries.
  
• Ease of Maintenance: Simpler mechanical design and widespread mechanic familiarity reduce downtime.
  
• Cost Effectiveness: Over the long term, easier access to parts and service can lower total cost of ownership.
  

Technical Considerations

• Mounting and Fitment: The physical size and mounting points differ between the Komatsu and Cummins engines, requiring custom engine mounts and possible frame modifications.
  
• Transmission Compatibility: The original Komatsu transmission must be matched carefully to the Cummins power curve to avoid issues.
  
• Cooling System Adaptations: Radiator and cooling hoses may require resizing or relocation to accommodate the new engine’s cooling needs.
  
• Fuel System Integration: The Cummins 6BT uses a mechanical fuel injection pump (commonly the Bosch P7100), necessitating fuel system rewiring and plumbing adjustments.
  
• Electrical System Changes: Wiring harnesses, sensors, and engine control modules need to be modified or replaced.
  

Step-by-Step Process Overview

• Engine Removal: The first step involves carefully disconnecting and removing the original Komatsu S6D105-B1 engine, including fuel lines, electrical connections, cooling system, and transmission linkage.
  
• Fabrication of Engine Mounts: Custom mounts are fabricated or adapted to secure the Cummins 6BT in the engine bay.
  
• Transmission Interface: Adapter plates or couplings may be needed to mate the Cummins flywheel and torque converter to the Komatsu transmission.
  
• Cooling System Upgrade: Radiator and piping are adjusted or replaced to ensure proper engine cooling.
  
• Fuel and Electrical Hookups: New fuel lines, filters, and electrical wiring are installed to match the Cummins engine requirements.
  
• Testing and Tuning: After installation, the engine is started and tuned for proper operation, including fuel delivery, idle settings, and throttle response.
  

Challenges Encountered

• Space Constraints: Limited engine bay space sometimes requires relocating auxiliary components.
  
• Electrical Compatibility: Integrating Cummins engine controls with Komatsu’s existing electrical system is complex and may require aftermarket solutions.
  
• Cooling Efficiency: Matching cooling capacity to the new engine's thermal load can be difficult, especially in hot climates or heavy-duty work.
  
• Transmission Matching: Ensuring smooth power delivery without overloading or damaging the transmission requires careful calibration.
  

Terminology Clarifications

• Engine Mounts: Brackets or frames that hold the engine securely in place.
  
• Flywheel Adapter Plate: A custom or aftermarket plate that mates the flywheel of one engine to the transmission of another.
  
• Torque Converter: A fluid coupling device transferring engine power to the transmission.
  
• Mechanical Fuel Injection Pump: A pump controlling fuel delivery mechanically rather than electronically.
  
• Wiring Harness: Bundle of wires connecting electrical components.
  

Real-World Case Study
One operator who completed this swap reported significant gains in machine uptime and ease of repair. The Cummins engine’s parts were readily available locally, and mechanics were more familiar with its maintenance needs. While the swap required about two weeks of workshop time and some custom fabrication, the long-term benefits in reduced repair costs and machine availability were substantial.
Summary List: Key Points of the Komatsu PC200LC-3 Engine Swap

• Original engine: Komatsu S6D105-B1 inline 6-cylinder diesel
  
• Replacement engine: Cummins 5.9 6BT inline 6-cylinder diesel
  
• Reasons: Parts availability, reliability, maintenance ease, cost savings
  
• Required modifications: Engine mounts, transmission adapter, cooling system, fuel and electrical systems
  
• Challenges: Space constraints, wiring integration, cooling efficiency, transmission matching
  
• Benefits: Improved uptime, serviceability, and local parts support
  
• Maintenance note: Cummins 6BT uses mechanical fuel injection and widely understood service procedures
  

Conclusion: Strategic Value of Engine Swaps in Heavy Equipment
Swapping the Komatsu PC200LC-3’s original engine for a Cummins 5.9 6BT represents a practical solution for operators seeking enhanced reliability and simplified maintenance. While technically demanding, the project pays off by extending machine life and reducing operational disruptions. This approach exemplifies how equipment owners adapt legacy machinery to modern needs using available technology and engineering know-how. Stories of successful swaps continue to inspire others in the heavy equipment field to consider similar upgrades tailored to their unique challenges.