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The venerable 5.9-liter Cummins powerplant is one of the most impressive diesel engines ever created, and the folks at CP-Carrillo [2] have their eye on helping enthusiasts to make big power.
“We’ve really tried to cover our bases with the diesel hybrid stuff,” says CP-Carrillo’s Bryce Mulvey.
“The biggest advantage to these is that we run a longer rod–it’s .856-inch longer than a stock-length rod. This helps with cylinder wear and rod angularity, and you get a longer dwell time at Top Dead Center, which gives you more torque.”
By running the longer connecting rod, a shorter compression-height piston and smaller wristpin is used; Mulvey says they use a Duramax-dimension wristpin in these applications instead of the Cummins-style pins. This allows them to design a shorter piston skirt without sacrificing strength. He feels that there is a misconception in the diesel world that massive wristpins and piston skirts are required, but by using the smaller, lighter parts, CP-Carrillo is after the strength improvement via weight reduction.
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“This combination allows you to lose two pounds of mass per cylinder, and twelve pounds of rotating weight overall. What’s the advantage to reducing rotating weight? The engine will rev faster, spool faster, and turn more RPM,” he says.
All of these pistons come with a hard anodized coating, and a special ring package measuring 1/16, 1/16, 2.0mm. These rings are constructed from M2 steel–what you’d typically find in a Top Fuel application–that have been specially designed for use in these diesel engines. Skirt shapes are designed to permit tighter piston-to-wall clearance: between .0055-inch and .006-inch clearances as opposed to the .010 to .012-inch PTW clearance used with other piston forgings.
Mulvey says that the company has performed many hours of durability testing with these combinations; in addition their in-the-field testers have thousands of miles on their engine combinations and with no adverse effects. These are made for the guy who wants 1,200-1,500 horsepower but still wants to have a street truck. Isn’t technology amazing?