Cummins vs Powerstroke vs Duramax

Before diesel engines became prominently featured in heavy-duty trucks, they could be found in ships, trains, and submarines. Originally used in the shipping industry, the diesel engine was invented in the late 19th century by a man named Rudolf Diesel. In the 1970s, diesel engines became even more relevant when gas prices skyrocketed. In order to combat rising fuel costs, automobile manufacturers began offering diesel engines as they claimed greater fuel efficiency and higher miles per gallon. Since then, diesel engines have become an integral part of our society.

While diesel engines can mainly be found in heavy-duty trucks, Ford and Chevy are beginning to offer diesel engines in their light-duty pickup trucks. In early 2018, Ford announced it will be offering the first F-150 diesel with a Power Stroke engine, while Chevy revealed shortly after that a 3.0L Duramax diesel engine will be available for the redesigned 2019 Silverado 1500. Ram trucks first offered a 3.0L EcoDiesel engine for the Ram 1500 in 2014. Although the EcoDiesel is not a famed Cummins engine, perhaps a Ram 1500 with a Cummins diesel engine is not too far from the horizon.

But what sets the Cummins vs Powerstroke vs Duramax diesel engines apart from each other? How did these three diesel engines become some of the greatest pieces of machinery ever created? Let’s take a look at the formation of the Duramax, Powerstroke, and Cummins and how these engines have evolved into what they are today.

Cummins vs Powerstroke vs Duramax: Specs

While the 6.7L Cummins and the 6.7L Power Stroke share the same displacement, the 6.6L Duramax is a pretty close match. Both the 6.6L Duramax and 6.7L Power Stroke are V8 engines, with the 6.7L Cummins being an inline six-cylinder diesel engine. Horsepower and torque numbers are similar between the three diesel engines, but the Cummins engine leads the pack with its torque rating breaching the four-figure threshold. Other differences include engine block and cylinder head construction, the compression ratio, bore and stroke, as well as the firing order. However, they share similar fuel requirements and fuel systems.

Cummins Engine

Beginning of the Cummins Engine

Some people would associate the Cummins diesel engine with Ram trucks, but they’ve been around much longer than that. Cummins Engine Company formed in 1919, named after founder and entrepreneur Clessie Lyle Cummins. The very first diesel engine that Cummins created was for farm use, which was sold in the Sears Roebuck and Co. catalog. However, this venture was not profitable as a loophole allowed farmers who had purchased the engine to return them after using them for the season. But that didn’t stop Cummins.

After producing diesel engines for work vehicles, trucks, and buses, Cummins decided to take the diesel engine to a new level when he created the first diesel-powered passenger car by swapping out the engine in an Auburn 851 sedan for his new Model A six-cylinder diesel engine. On June 17, 1935, he left New York City to drive all the way to Los Angeles in the modified sedan. After traveling 3,774 miles, the Auburn finally arrived in Los Angeles on July 4, 1935. Can you guess how much it cost in diesel fuel to travel all the way across the United States during that time period? For the entire journey, it only cost $7.63. In current times, that would equate to $138.05. Not too shabby.

Dodge Ram Adopts Cummins Diesel Engine

Ram pickup trucks first adopted the Cummins diesel engine in 1989 — a 5.9L six-cylinder 12V turbodiesel engine capable of putting out 160 horsepower and 400 lb.-ft. of torque. Ford and Chevy trucks also had diesel engines at this time, but the Cummins turbodiesel was on an entirely different level. Turbocharged and direct-injected, the 359 cubic-inch Cummins engine far surpassed the competition. An intercooler was added to the engine in 1991, but the first big change came in 1994. The old injection pump, which was a Bosch VE rotary unit, was replaced by the Bosch P7100. The P7100 maintained the original horsepower and torque ratings for the automatic transmission but bumped up the manual transmission numbers to 175 horsepower and 420 lb.-ft. of torque.

Updates to the Cummins Engine

The next substantial update occurred in 1998, when the P7100 injection pump was swapped out for the electronically controlled rotary injection pump, the VP44. With 24 valves, the turbodiesel engine surpassed the 200-hp mark, creating 215 horsepower and 420 lb.-ft. of torque with the auto transmission and 235 horsepower and 465 lb.-ft. of torque with the manual transmission. In 2001, an optional high-output Cummins engine added 10 extra horses and pushed torque up to a massive 505 lb.-ft. By 2003, the injection pump was replaced yet again, this time by the common-rail Bosch CP3 high-pressure fuel pump, which allowed for multiple injection events that helped reduce engine noise.

6.7L Cummins Diesel Engine

In 2007, the 5.9L Cummins engine was redesigned for the first time, increasing displacement to 6.7 liters. With a bore of 4.21 inches and a stroke of 4.88 inches, the new 6.7L Cummins engine featured a variable geometry turbocharger. Not only was the 6.7-liter turbodiesel engine more powerful than ever with a whopping 350 horsepower and 650 lb.-ft. of torque, it was also quieter than ever with 50% reduced noise. In 2018, the 6.7L Cummins is still the same diesel engine that Ram trucks offers in its heavy-duty pickups, producing up to 800 lb.-ft. of torque along with 370 horsepower. For the past 30 years and counting, the Cummins diesel engine has been a main feature in Ram’s heavy-duty truck line, and it doesn’t look like it’s going anywhere anytime soon!

Beginning of the Cummins Engine

The Cummins engine was redesigned yet again for the 2019 Ram HD trucks, pushing the limits of this turbocharged diesel engine. This engine boosts the torque rating of the engine to an impressive 1,000 lb-ft. The compression ratio decreased from 17.3:1 to 16:2:1, but the turbocharger's size grew, now capable of producing 33 psi of boost. The overall engine weight is 62 lbs less than the previous iteration of the Cummins engines, weighing in at 1060 lbs. This decrease in weight is due to the use of a compacted graphite iron engine block. In order to handle the increased power and boost, the updated engine has a fortified alloy crankshaft with a 10-bolt crank flange and redesigned forged connecting rods, along with new piston bearings. One of the last major changes to the updated Cummins diesel engine is the new fuel-delivery system and fuel rail. The new fuel pump can deliver fuel at 29,000 psi and contains a "filter in filter" NanoNet® filtration system.

6.7L Cummins Diesel Engine Features:

• Cast-iron engine block and cylinder heads
• Bosch high-pressure common-rail fuel system
• Holset HE351VE variable geometry turbocharger
• 16.2:1 compression ratio
• B20 biodiesel compatible
• Inline 6 cylinder
• Exhaust brake function

Power Stroke Engine

When General Motors began selling the 6.2L Detroit Diesel V8 engine in 1982, Ford felt compelled to start offering diesel engines in order to keep up with the competition. As a result, Ford released the 6.9L IDI diesel engine for its heavy-duty pickups. Manufactured by International Harvester, the IDI diesel engine featured indirect injection, hence the “IDI” nameplate. As a portion of International Harvester was bought out by Tenneco Inc., the name of the company changed to Navistar International. That’s why you see these engines branded as the International Harvester/Navistar engines. With the first-generation diesel engines producing 175 horsepower and 318 lb.-ft. of torque, it was a tough competitor for GM’s Detroit Diesel. Engine displacement increased to 7.3L in 1988 and by 1993, a turbocharger was introduced to the mix. With the 7.3L turbodiesel engine, horsepower rose to 190 with torque coming in at a decent 388 lb.-ft. A year later, in 1994, Ford and Navistar International debuted the first Power Stroke diesel engine.

First Power Stroke Diesel Engine

With an electronically controlled fuel system, Ford’s 7.3L Power Stroke engine featured direct injection that made it more efficient as well as more powerful. Boosting horsepower to 215 and torque to 425 lb.-ft., the first installment in the Power Stroke series made waves throughout the truck industry. Based on Navistar’s T444E engine, the 7.3L Power Stroke engine and the successive diesel engines produced after the first generation are exclusive to the Ford Motor Company. The Power Stroke engine was constructed with a cast-iron block and cast-iron cylinder heads. An intercooler was added in 1999, along with reduced noise, vibration, and harshness. Horsepower and torque were further increased by the time the 7.3L ceased production, with final numbers coming in at 275 horsepower and 525 lb.-ft. of torque. Known by some as one of the greatest diesel engines of all time, Ford’s 7.3L Power Stroke was an industry leader for nearly a decade.

6.0L Power Stroke Engine

After the massive success of the 7.3L Power Stroke engine, Ford and Navistar were pressured to redesign the engine due to stricter emissions guidelines. In 2003, the 6.0L Power Stroke was produced alongside the 7.3L engine, which went out of production completely in 2004. To comply with regulations, the engine was equipped with exhaust gas recirculation, or EGR, a feature not found on any of Ford’s previous diesel engines. Although it had a laundry list of problems such as head gasket failure, clogged EGR valves, oil cooler failure, and fuel injection control module failures, the 6.0L had more power than its predecessor, sporting 325 horsepower and 570 lb.-ft. of torque.

6.4L Power Stroke Engine

While Ford’s first diesel engine had knocked it out of the park, the second installment of the popular engine didn’t do so well. With several issues regarding dependability, Ford redesigned the engine yet again in 2008. Producing 350 horsepower and 650 lb.-ft. of torque, the 6.4L boasted more power than the 6.0L, but it was still lacking when it came to reliability. While the Cummins and Duramax engines had already been using a high-pressure common-rail fuel system, the 6.4L was Ford’s first time using the technology. However, the 6.4L didn’t remain in production for long. After a heated lawsuit, Ford and Navistar ended their partnership at the end of 2009. While the 6.4L was an improvement from the 6.0L, the damage had already been done to the Power Stroke name. Ford wanted to branch out and begin producing its own diesel engine. So in 2011, Ford introduced a new 6.7L Power Stroke engine — the Scorpion.

6.7L Power Stroke Engine: The Scorpion

Ford’s first solo venture in the competitive world of diesel engines was the 6.7L Power Stroke engine, which was nicknamed the Scorpion. Released in 2011, the 6.7L was totally redesigned with an emphasis on enhancing both performance as well as dependability. Ford needed a new and improved Power Stroke engine in order to redefine the brand. With the same displacement as the popular 6.7L Cummins turbodiesel, the Scorpion doesn’t mess around, sporting 390 horsepower and 735 lb.-ft. of torque when it was first released. While the 6.7L Power Stroke was originally equipped with a twin turbocharger, known as DualBoost, a single turbo now adds even more horsepower and torque to the engine. For 2018, the engine boasts a massive 450 horsepower and 935 lb.-ft. of torque.

6.7L Power Stroke Turbo Diesel Features:

• Strong, yet lightweight compacted graphite iron engine block
• Inverse-flow configuration with the turbocharger and exhaust manifolds mounted between the cylinder heads
• Large, single turbocharger
• Smart exhaust brake function
• B20 diesel compatible
• Pushrod/rocker arms valve operation

Duramax Engine

The first diesel engine found in early Chevy trucks was a 5.7L Oldsmobile engine that was produced in-house by General Motors and capable of producing 120 horsepower and 220 lb.-ft. of torque. Starting in 1982, GM moved production out of house, partnering with Detroit Diesel to create new diesel engines for their trucks. Thus entered the 6.2L Detroit Diesel V8 engine, which put out 130 horsepower and 240 lb.-ft. of torque. The 6.2L diesel engine lasted until 1994, when it was replaced with the 6.5L Detroit Diesel engine, which was turbocharged. After a nearly 20 year working relationship, General Motors ended their relationship with Detroit Diesel to form a new partnership with Isuzu. Working together, the two formed an entirely new class of diesel engines: the Duramax.

Duramax LB7

Since Chevy was having a difficult time competing with the powerful diesel engines found in Ford and Dodge trucks, the Duramax engine was supposed to help bridge that gap. The first-generation 6.6L Duramax turbodiesel engine was released in 2001, sporting 300 horsepower and 520 lb.-ft. of torque. Dubbed the Duramax LB7, there were four valves for each of the eight cylinders. What was really special about the LB7 was that it featured a high-pressure, common-rail Bosch CP3 injection pump, something that hadn’t yet been used on Dodge’s Cummins engine or Ford’s Power Stroke engine. Cummins didn’t receive the Bosch CP3 injection pump until two years later in 2003, with the Power Stroke coming in last to receive a high-pressure common rail injection pump. Constructed with aluminum cylinder heads, the Duramax LB7 came with a standard manual transmission but could be ordered with the Allison five-speed automatic transmission. Although the LB7 was a reliable engine, the Duramax was updated in 2004.

Duramax LLY & LBZ

The next-generation Duramax, released in 2004, was known as the LLY engine. Redesigned valve covers differentiate the LLY engine from the LB7. Notable updates other than the valve covers include a variable geometry turbocharger, reduced emissions, and slight increases in horsepower and torque. Enhancements were made to the variable-geometry turbo with the release of the Duramax LBZ in 2006. Adding even more power and efficiency, the upgraded diesel engine featured a higher-pressure fuel injection system, redesigned pistons, and a more durable engine block design. With the improvements, horsepower reached an impressive 360, and torque increased to 650 lb.-ft.

Duramax LMM & LML

After the Duramax LBZ came the release of the LMM in mid-2007. The main focus of the updates to the LMM Duramax engine revolved around reducing emissions to comply with new regulations. As such, the LMM featured several new additions including a Diesel Oxidation Catalyst, or DOC, as well as a Diesel Particulate Filter, or DPF. Emissions were also an important factor when the next Duramax engine came out in 2011. The Duramax LML featured a urea-injection system and higher-pressure fuel injection, producing 397 horsepower and 765 lb.-ft. of torque. Capable of using B20 diesel fuel, which is a fuel mixture composed of 80% diesel and 20% biodiesel, the LML lasted until 2016 until being replaced by the more powerful Duramax L5P.

Duramax L5P

In 2017, General Motors debuted the L5P Duramax engine, which helped Chevy and GMC compete with the high horsepower and torque numbers found in the Cummins and Power Stroke engines. Improved strength, power, efficiency, and durability brought the horsepower up to 445 horsepower and torque to 910 lb.-ft. Not only is the LP5 turbodiesel engine more powerful, it’s also quieter than ever with a 38% reduction in noise.

6.6L Duramax L5P Features:

• Exhaust Gas Recirculation System
• Electronically controlled variable-geometry turbocharger
• Venturi Jet Drain Oil Separator
• Cold-Start System for increased performance in cold weather conditions
• Stronger cast-aluminum cylinder heads and cast-iron cylinder block
• Higher boost pressure for increased horsepower and torque
• Lower exhaust emissions
• B20 biodiesel compatible
• Allison 1000 Series 6-speed automatic transmission

Sources: 6.7L Power Stroke Diesel Specs and Information, Diesel Hub | 6.7L Cummins Specs, Info, and Resources, Diesel Hub | Duramax Timeline, Diesel Hub | Cummins vs Duramax vs Power Stroke-2020 Diesel Engines, MotorTrend | Engineering Explained: Gasoline vs Diesel Engines, CarThrottle | Engines, Cummins | What are the Best Diesel Engines to Buy for Your Next Pickup Truck? Full Review, Car Engineer

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