Dodge wasn't the first company to drop a diesel engine into a medium-duty pickup, but Cummins-powered Dodges nonetheless heralded a quantum shift in the way such trucks would forever roll. Dodge was the first company to marry a pickup truck with an engine designed for a tractor-trailer; the effect was only slightly less shocking than using a nuclear reactor to toast bread.
There's no hyperbole in saying that Cummins is to the road-going diesel what Henry Ford was to the automobile itself. Clessie Cummins opened the doors of his namesake company in 1919 with the intention of perfecting and capitalizing on principles pioneered by Rudolph Diesel in the 1890s. Cummins first engine was the Model H, the first engine ever to come with a 100,000-mile warranty.
Although Cummins engines had seen use in everything from trucks to Indy 500 racers, Clessie's vision didn't really come into its own until the late 1960s and early 1970s. Cummins had already had a commanding lead over most competitors for over 20 years when they purchased British-owned turbo manufacturer Holset Engineering in 1973. However, it wasn't until afterward that Cummins proved the immense mass-market potential of bolting a turbo to a diesel. Prior to the rise of turbo charging, diesels were "torque-y," but loud, underpowered, dirty and inefficient.
The B-Series Debuts
Cummins spent the better part of a decade refining the road-going turbo diesel before finally designing one from the ground up. Unlike previous engines, the B-Series was designed from the outset with turbocharging in mind. From 1984 to 1988, this mountain motor saw use only in Case agricultural equipment and applications for commercial trucks rated at a maximum of 66,000 pounds gross vehicle weight.
Dodge Ram 6BT
Dodge engineers searched for a high-powered replacement for the expensive and underpowered D-Series Mitsubishi non-turbo diesel used since the 1970s. Chrysler execs initially resisted the engineers, insisting that the 5.9-liter 6BT would never outsell the 13,000-unit build limit that they imposed. They were wrong. Cummins already had such brand recognition in the medium-duty truck demographic that the company received 22,000 build requests before the first Cummins-powered Dodge ever turned a wheel.
The Cummins B-Series has come in dozens of different configurations over the years, but four basic generations define the design -- including the four-cylinder 4BT. The first 6BT, from 1989 to 1993 was a non-intercooled model using a single turbo and mechanical fuel injection to produce 160 horsepower and 400 foot-pounds of torque. Later models would produce 175 horsepower and 420 foot-pounds in 1994 to 1995, and 180 horsepower and 420 foot-pounds from 1996 to 1998.
Dodge replaced the standard 6BT with the Interact System B engine in 1998. Among a number of other refinements, this straight-six engine used a Bosch VP44 variable rotary fuel pump, higher compression and forged steel connecting rods. While this move was more to meet emissions requirements than anything else, power climbed to 235 horsepower and 460 foot-pounds with the manual transmission -- 215 horsepower and 420 foot-pounds with the automatic -- and more recent high-output versions with 17.2-to-1 compression produced 245 horsepower and 505 foot-pounds of torque.
ISB CR Specs
Computer-controlled common-rail injection had been around since the Interact System B first debuted, but didn't make its way to the Dodge truck line until 2003. The common-rail injection system was as revelatory to the diesel market as multi-point fuel injection had been to the gas market more than a decade before. Not only did the ISB CR produce 305 horsepower and 555 foot-pounds of torque -- later 325 hp and 600 foot-pounds -- it did so while offering better fuel economy and emissions output than any previous models.
The B6.7 is the newest Cummins engine. It displaces 0.8 liters more than the ISB, making it the largest straight-six light-truck engine in production today. It uses electronic common-rail injection for power and fuel economy and a variable-geometry turbo for a wide torque band and flexible power delivery. Current models produce about 350 horsepower and 800 foot-pounds of torque in Dodge Ram form.
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