The History of the Cummins Diesel Engine

Chronologically Cataloguing the Cummins

While most only know Cummins for its turbocharged, inline engines used in industrial and automotive applications, the company's history far predates any mergers with Dodge, Kubota, Freightliner, or Kenworth. Check out the timeline below for a comprehensive list of Cummins' major milestones over the past century, beginning with Clessie Cummins' first single-cylinder, kerosene-powered engine. 

Humble Beginnings—Clessie Cummins (1919)

In 1919, Clessie Cummins, co-founder of the engine manufacturer, developed the first-ever Cummins engine. However, it looked far different from the 5.9L and 6.7L engines in modern-day pickups and heavy equipment. This engine featured only a single cylinder and ran on diesel, kerosene, or essentially any flammable liquid. The same year, Clessie co-founded Cummins Engine Company alongside banker William G. Irwin.

Moving Forward—the Model F Engine (1924)

Five years later, Cummins introduced its first successful home-grown engine design—the Model F. This engine utilized either one or two cylinders featuring a 5.5-in. bore and 7.5-in. stroke. The engine was a massive success, beginning Cummins' long-running history of innovation.

Four Cylinders—the Model U Engine (1928)

In 1928, Cummins released its first-ever four-cylinder engine, the Model U. This engine helped redefine what was once deemed possible for the diesel engine, furthering the eventual goal of Cummins-powered automobiles.

An Industrial Staple—the Model K Engine (1929)

The following year, Cummins debuted an all-new engine family—the Model K. Featuring advancements at nearly every level, the Model K quickly became a staple in the industrial market, as did its direct descendants, including the Model KO, L, and LR.

The First Cummins-Powered Passenger Vehicle (1929)

While the infamous Wall Street crash of 1929 spelled doom for many innovators, Clessie Cummins devised a plan to explore different applications of his diesel power plants. On Christmas morning, 1929, Clessie debuted a fully functional Cummins diesel-powered Packard—the first Cummins-powered automobile.

Race Ready—The First Cummins-Powered Racer (1931)

With proof of concept, Clessie Cummins went to work developing the first Cummins-powered race car to compete in the Indy 500. Marketing efficiency over speed, Cummins vowed to have the only race car that wouldn't pit. Ultimately, the Cummins-powered number eight racer finished 13th of 33 competitors.

Heavy-Duty Transport—the Cummins H672 (1932)

In 1932, Cummins introduced the H672 heavy-duty diesel engine, which would become a fixture in the heavy-duty transport industry for the next seven decades. This innovative engine was the direct precursor to the 5.9L Model B.

Pole Position Leader—the Cummins JBS-600 (1952)

Skipping forward two decades, Cummins reentered the Indy 500 with its new and improved turbocharged JBS-600. Though the car was forced to retire due to mechanical failure, it assumed the pole position during the race with a mind-boggling 139-mile-per-hour top speed. The car also went down as the first-ever turbocharged Indy 500 racer. Whether engineers knew it or not, this vehicle spelled out the future of Cummins engines.

Cummins Purchases Holset (1973)

After realizing the effectiveness of forced induction in diesel applications, Cummins purchased Holset to begin manufacturing its turbochargers in-house. The merger proved highly successful, as Holset turbochargers can still be found on Cummins engines today.

The First Holset-Turbocharged Cummins (1980)

In 1980, Cummins released its first mass-produced turbocharged engine featuring a Holset turbocharger. Within years, a similar engine would power the first-ever diesel Dodge pickup.

A Legend is Born—the Cummins B5.9 (1984)

1984 saw the release of a titan—the B-series, 5.9L Cummins engine, which would dominate the heavy-duty truck and industrial sectors for years.

The First Cummins-powered Dodge Ram (1987)

Between 1984 and 1987, Cummins had the bright idea to place the same B5.9 Cummins engine into a heavy-duty Dodge pickup. The company quickly acquired a 1985 Dodge Ram D350 as its first test mule, removing the dependable 360 V8 for the relatively untested 6BT Cummins. What was the result? As Dodge Truck General Product Manager Dale Dawkins said, "It's even better than we hoped."

The ISX15—A Heavy-Duty Icon (1998)

In 1998, Cummins released the ISX15—a remarkable industrial engine that served customer needs well into the 21st century.

The First Variable Geometry Turbocharger (2000)

In 2000, Holset developed the world's first VGT (variable geometry turbocharger). This design featured adjustable vanes to direct the flow of exhaust gasses, helping with efficiency, backpressure, and torque production throughout the RPM range.

The One-Millionth RAM Engine (2003)

Cummins' one-millionth engine intended for use in Dodge Ram pickups rolled off the assembly line in 2003, marking a significant milestone for the company. This number cemented Cummins as an automotive engine manufacturer.

100 Years of Cummins (2019)

In 2019, Cummins celebrated its 100th anniversary. From humble beginnings, the manufacturer became a dominant force in the heavy-duty, industrial, agricultural, and automotive markets.

The Cummins-Powered RAM

Cummins-powered RAM pickups are a staple in the heavy-duty truck market. The engine carries a cult following for its unmatched reliability and power potential—I own a 2008 Dodge Ram 2500, packing the legendary 6.7L Cummins. The engine shows no signs of slowing down, even with 200,000 miles on the clock and counting!

What Drove the Invention of the Cummins RAM?

So, what drove the partnership between Cummins and Ram in the first place? While Cummins is often viewed as the original diesel engine used in heavy-duty pickups, this isn't the case. The 6.9L International IDI found in the Ford F-Series, and the 6.5L Detroit Diesel in GM HD pickups predate the Cummins Dodge Ram. 

Not wanting to fall behind the competition, Dodge and Cummins agreed the partnership would be mutually beneficial. Dodge needed a unique selling point to drive Ram sales, while Cummins wanted to enter the passenger vehicle market.  

In the end, the merger was one of the best decisions of either manufacturer, as sales and profits skyrocketed for both companies.

Cummins-Powered RAM Engine Generations

Though Cummins-powered RAM trucks have maintained a dominant position since their conception, the engine has undergone several revisions since its release in 1987.

5.9L 12V (1989–1997)

The 5.9L 12V Cummins is often viewed as the most reliable diesel engine of all time. This fully mechanical turbo-diesel engine is mechanically timed and governed and features no failure-prone electronics. 

The motor received several upgrades throughout the 12V 5.9L Cummins production life, which stretched across two generations of Dodge Ram pickup. In 1994, upon the release of the second-generation Dodge Ram, the engine received a new turbocharger, an intercooler, and updated injectors, pistons, and emissions. 

Performance for the 12V 5.9L Cummins varies by year, but it ranges between 160 and 215 horsepower and 400 to 440 lb/ft of torque.

5.9L 24V (1998–2007)

Between 1997 and 1998, the 5.9L Cummins received a significant overhaul. The engine gained two valves per cylinder, superior cooling, and a redesigned Bosch-VP44-based electronic fuel system, producing between 215 and 245 horsepower and 420 to 505 lb/ft of torque. 

2003 saw the introduction of the Common Rail Cummins, which features an all-new Bosch-CP3-based fuel system, a redesigned engine block and cylinder head, and a new turbocharger. Essentially, the entire engine was altered aside from its general design and displacement. This new engine continued through 2007 with numerous small changes, including oil passage designs in the block, turbochargers, and tuning. 

Between 2003 and 2007, power numbers varied wildly. At its lowest, the Common-Rail-Cummins-powered Dodge Ram produced 250 horsepower and 460 lb/ft of torque. The engine design produced 325 horsepower and 610 lb/ft of torque at its highest.

6.7L 24V (2007.5–Current)

In the second half of 2007, Cummins introduced the second iteration of the Common Rail Cummins—the 6.7L. This engine significantly bumped displacement for the first time since a Cummins engine was used in a Dodge Ram. The engine remained virtually identical from 2007.5 to 2018, aside from tuning and advancements in emissions. Between these years, power varied from 350 horsepower and 650 lb/ft of torque to 385 horsepower and 930 lb/ft. 

In 2019, RAM released the fifth generation HD pickups, which featured a redesigned 6.7L Cummins. Much like the total redesign of the 5.9L motor in 2003, the new 6.7L engine shared little in common with the previous year. This new engine, offered in standard and high-output variants, produces a staggering 470 horsepower and 1,075 lb/ft of torque.

The Impact of Cummins' and RAM's Partnership

While the Cummins wasn't the first diesel engine to find its way into modern passenger vehicles, it's undoubtedly one of the most influential. The merger prompted other manufacturers to rethink their own diesel engines, influencing the production of legendary motors such as the 7.3L Power Stroke and the 6.6L Duramax. If not for Clessie Cummins' initial designs and unmatched drive, the modern heavy-duty truck landscape would look drastically different. 

When it comes to modifying your Cummins-powered RAM 2500 or 3500, RealTruck has the parts and accessories to get the job done. For inspiration, check out our selection of parts comparisons, build guides, and more on RealSource—your source for articles on all things truck, Jeep®️, and more.