INSIDE THE 1,000 LB-FT 6.7L CUMMINS
A DEEPER LOOK AT THE 6.7L CUMMINS, 1,000 LB-FT
Now that the cat is out of the bag and we know the high output 6.7 Cummins delivers 1,000 lb-ft of torque—the greatest ever produced by an OE engine scheduled for a pickup truck—time it's to investigate what efforts Cummins has taken to ensure that this power plant is as resilient as its forerunners. We can tell you that nearly every component essential to the long-term survival of this engine has been strengthened or reinforced with stronger parts.
The compressed graphite iron block, forged connecting rods, upgraded cylinder head with larger head bolts, and all the supporting components show that Cummins constructed this engine with longevity in mind. In fact, there is opportunity for expansion in the future. Additionally, a larger variable geometry Holset turbocharger (with a forged-milled compressor wheel) delivers more than 30 psi of boost and a higher pressure is created. Hydraulic lifters also do away with the necessity for routine valve adjustments. The Bosch common-rail injection system generates the most modern, cleanest emissions. For a detailed examination of each element that goes into making the 6.7L Cummins the king of torque, keep reading.
Return of the Ram 3500 HD to the Top
With the launch of the high output 6.7L Cummins, Ram has formally defeated the Big Three in the race to 1,000 lb-ft. Furthermore, fully equipped 3500 variants have a class-leading 35,100 pound towing capacity.
Larger Block
A compacted graphite iron (CGI) crankcase from Tupy is now available for the high output 6.7L Cummins, which is perfect for the increased cylinder pressure this engine probably experiences over prior models. This is the first time the engine has never been built with gray cast iron. Increased hardness and fatigue strength, better ductility and improved tensile strength, as well as significant weight savings, are all benefits of casting a block from CGI (this block is 60 pounds lighter). Although the specific figures for the Cummins crankcase are unknown, we do know that CGI can be up to 75% stronger than regular gray iron. Inside the deep-skirt block, a stronger alloy crankshaft with a 10-bolt crank flange is secured by four-bolt main caps.
Lighter and Lower-compression pistons
The durability is increased by cast-aluminum pistons with low-friction rings and lighter rotating assembly parts with larger wrist pin sizes. The compression ratio of the H.O. mill has decreased to 16.2:1 from 17.3:1 in the past. The fact that Cummins has returned to using forged-steel connecting rods (rather than powdered metal) underneath the pistons further supports our idea that this engine was built with lots of room for future expansion in terms of both horsepower and torque.
Changes to Cooling and Oiling
With 17 or more tons in tow and four digits of available torque, both the cooling and oiling systems have been enhanced to ensure optimal operating temperatures and lubrication. It is probably certainly equipped with a bigger radiator, a stronger engine fan, and a larger oil and water pump. Ram asked that the housings for the water and oil pumps also be made of aluminum to further minimize weight.
Larger Bolt Heads
We may assume that the head bolts holding the cylinder head to the CGI block have larger diameters even though we don't have access to the exact measurements. Our educated guess is that Cummins altered the head bolt diameter from 12mm (left) to 14mm (right). The larger diameter fasteners will be crucial for maintaining the head gasket for hundreds of thousands of kilometers with increased cylinder pressure.
Rolling Hydraulic Lifters
The largest advancement is this engine's usage of hydraulic lifters in the valvetrain, a first for the 6.7L Cummins. Because solid roller lifters are self-adjusting, their removal causes the valvetrain to operate more quietly, extends the life of the valvetrain and cam, and prevents valve running after 150 000 miles.
Rockers and Heads
As you may have assumed given the existence of hydraulic lifters, the rocker arms have no clearance for valve adjustment under the valve cover. The head itself has 24 valves per cylinder with cast-iron construction, and has modern exhaust valves and stiffer valve springs to better tolerate the increased heat.
Greater Turbo Flow
It uses a Holset variable geometry turbocharger, which is slightly different from the HE351VE turbochargers used on older engines, to deliver 1,000 lb-ft of torque at just 1,800 rpm. To improve exhaust flow, taller turbine vanes are employed in the exhaust housing, and the middle section uses stronger load bearings. For improved efficiency on the compressor side, a forged-milled compressor wheel is utilized, which is said to measure the same 60mm at the inducer. At full power, the Holset can produce 33 psi of boost right away.
Different Exhaust Manifolds
The variable geometry turbo has a exhaust manifold that was installed to suit it. Using what appears to be a T3 divided flange, it installs the turbocharger in a position that is counterclockwise (or tilted) downward, toward the passenger side of the firewall. One of the oddest-looking units we've ever seen on a Cummins is this one. As you can see, the turbo will also be positioned between Cylinders 4 and 5, rather than in the middle between Cylinders 3 and 4.
Enhanced Emissions, Enhanced Pressure, and Enhanced Efficiency
The common-rail fuel system is still provided by the Bosch business, albeit it has been modified and uses the CP4.2 high-pressure fuel pump rather than the CP3 fuel pump that was first introduced in the 1960s. Even though the maximum pressure rating for this twin-piston pump is 39,000 psi, Cummins and Ram assert that the peak injection pressure in this application will be closer to 29,000 psi. Using the CP4.2 allows for future growth, just like with the CGI block, forged steel rods, and larger head bolts. It's unclear if the injectors are solenoid or piezo in design, despite the fact that we're leaning toward piezo injectors.
