Chrysler built a fuel efficient diesel truck engine in 1938, then killed the project
The 1989 Dodge Ram with its Cummins engine is a diesel truck icon. That first-gen Ram was the first factory-built intercooler turbo-diesel. With the Cummins 6BT, engineered for industrial applications, its power and reliability are the stuff of legend. But Chrysler corporation almost gave us a technologically advanced diesel I6 in a light truck 50 years earlier.
It’s honestly not a huge shock Chrysler was dabbling in light diesels in the 1930s. Constantly striving to keep up with Ford and GM, Chrysler drove many innovations in automotive engineering. Anti-freeze. Replaceable oil filters. Motor mounts. Hydraulic four-wheel disc brakes. The first mass-produced power steering system. It all came from Chrysler. Heck, it was Walther Chrysler who enlisted Orville Wright to build a wind tunnel so he could design the first aerodynamic car in history.
Chrysler’s diesel-powered I6 truck engine
Yet the light diesel engine was one of Chrysler’s greatest engineering challenges. The 331 project was a small I6 powered by diesel fuel. The metallurgy challenges of a high-compression diesel engine for a light truck were intimidating enough. But Chrysler also pioneered an indirect ignition system with “Twin Cyclone” combustion chambers to pre-ignite the air/fuel mixture. It enlisted Bosch for fuel injectors capable of 2,200 PSI.
By all accounts, the resulting 331 was comparatively light, powerful, and trounced gasoline truck engines in fuel efficiency. According to Chrysler’s own engineers, at 2,400 rpm the gasoline version of the I6 used 10.7 gph while the diesel sipped just 6.6. Idle down to 800 rpm and the gas engine stayed at 10.7 gph while the diesel dropped to 4.3 gph. [Diesel World Mag].
Chrysler debuted its new engine at the 1938 NYC Motor Truck Show, to an amazed audience. There was only one problem: Where would Dodge/Chrysler’s customers buy diesel? And forget about finding a technician capable of fixing a diesel truck.
Given a bit more time, Chrysler might have been able to set up a fuel network and technician training programs. This is what Mack and Cummins had to do to sell heavy-duty diesel engines. But then WWII broke out and the automaker had its work cut out building military trucks. It killed the 331 project. When it finally decided to take another swing at a diesel truck in the 1980s, it enlisted Cummins’ help. The rest is, as they say, history.
You can see the diesel 331 powered Chrysler trucks yourself in the video embedded below:
