Posted on: - 10/14/2025

When it comes to diesel performance and reliability, the Cummins name is legendary. Since its introduction in Dodge trucks in 1989, the Cummins turbo diesel engine has built a reputation for power, durability, and aftermarket support. Over the years, the engine has evolved through multiple generations, each offering improvements in horsepower, torque, emissions compliance, and fuel efficiency.

1989 to 1993 – 5.9L 12-Valve (1st Gen)

  • Engine Code: 6BT
  • Power: 160 hp / 400 lb-ft
  • Fuel System: Bosch VE rotary injection pump
  • Notable Features: This was the engine that started it all. It featured a cast-iron block and head, forged internals, and mechanical fuel injection. Known for simplicity and reliability.

1994 to 1998 – 5.9L 12-Valve (2nd Gen)

  • Engine Code: 6BT
  • Power: 175–215 hp / 420–440 lb-ft (varied by year/transmission)
  • Fuel System: Bosch P7100 inline injection pump
  • Notable Features: More power and tuning potential thanks to the P-pump. This generation is beloved by diesel enthusiasts for its mechanical simplicity and responsiveness to performance upgrades.

1998.5 to 2002 – 5.9L 24-Valve VP44 (Late 2nd Gen)

  • Engine Code: ISB 5.9
  • Power: 215–245 hp / 420–505 lb-ft
  • Fuel System: Bosch VP44 electronic rotary pump
  • Notable Features: Introduced 24 valves and electronic fuel control. These engines are known for better drivability but had some reliability concerns around the VP44 and lift pump failures.

2003 to 2007 – 5.9L Common Rail (3rd Gen)

  • Engine Code: ISB 5.9
  • Power: 305–325 hp / 555–610 lb-ft
  • Fuel System: Bosch CP3 common rail injection
  • Notable Features: Major step forward in refinement and tuning potential. These engines are quieter, cleaner, and offer better performance. Highly sought after for swaps and performance builds.

2007.5 to 2012 – 6.7L Common Rail (Early DPF Era)

  • Engine Code: ISB 6.7
  • Power: 350–370 hp / 650–800 lb-ft
  • Fuel System: Bosch CP3 common rail
  • Notable Features: First use of the 6.7L displacement. Introduced emissions equipment including DPF and EGR systems. Stronger bottom end and increased torque output. Some early issues with emissions-related components.

2013 to 2018 – 6.7L Cummins (HO and Standard Output)

  • Engine Code: ISB 6.7
  • Power: 350–385 hp / 660–930 lb-ft
  • Fuel System: Bosch CP3 common rail
  • Notable Features: Continued refinement with improved emissions reliability. High Output (HO) versions paired with Aisin transmissions produced significantly more torque. This era also saw the final model year (2018) offering a manual transmission.

2019 to Present – 6.7L Cummins (Current Gen)

  • Engine Code: ISB 6.7
  • Power: Up to 420 hp / 1,075 lb-ft (High Output)
  • Fuel System: Bosch CP4 (2019–2021), Bosch CP3 (restored in 2021 models)
  • Notable Features: Modern 6.7L Cummins engines offer unmatched torque and towing capability in a factory pickup. Advanced emissions systems and tuning make these trucks ideal for heavy-duty work and long-haul applications. Ram dropped the manual transmission option after 2018.

Final Thoughts

The evolution of the Cummins engine in Dodge and Ram trucks tells a story of constant innovation, power, and durability. Whether you’re running a classic 12-valve or a modern high-output 6.7L, Cummins engines have earned their place as one of the most respected names in diesel.

Adam_Blog
By: Adam