To those who are new to the diesel game, the Cummins B-series engine is thought of as an inline-six-cylinder engine that's used in Dodge trucks. In reality, the B-series product line consists of three-, four-, and six-cylinder, high-swirl, direct-injection engines with a displacement of 0.98L per cylinder and a bore of 4.02 inches and a stroke of 4.72 inches. The entire B-series family was designed to withstand high levels of turbocharging with conservative component loading.
6 = six-cylinder
B = B-series
T = turbocharged
5.9 = 5.9L
A Successful Design
When the B-series project was initiated by Cummins in September 1978, a special team was formed to focus resources, and the effort eventually grew to 214 people. The original B-series engines were manufactured at a joint-venture plant in Rocky Mount, North Carolina, that was owned by the Cummins Engine Co. and the J.I. Case Co.
The seven most important design objectives for the B-series engine were durability, reliability, emissions, performance, application adaptability, cost, and serviceability. In July 1983, production was started on the four-cylinder version for industrial applications. That was the first of new product introductions planned for the following three years. The engines were engineered to cover a broad power range in turbocharged and normally aspirated form. The original B-series engine enjoyed mechanical fuel distribution with 17mm closed-nozzle injectors.
Dodge And Cummins
In the early '80s, Chrysler was searching for a diesel powertrain to use in it's 3/4- and 1-ton trucks. By the end of 1983, industry sales of the larger pickup trucks were showing 22 to 25 percent diesel penetration, as established from market data representing Ford and General Motors products, respectively. Performance, durability, and fuel economy were the driving forces behind the diesel's acceptance.
The Cummins 6BT5.9 engine clearly possessed the necessary qualities to satisfy Dodge's market requirements. The modern design also had the compact size and weight that would be required for use in the '89-'93 line of Dodge trucks. In addition, Cummins' strong reputation among diesel truck owners and operators and its predominant presence in the Class 8 truck market was viewed as a strong advantage by Chrysler. In November 1984, Chrysler completed a nonfunctional hardware mockup of the proposed engine installation. A running concept vehicle was completed by Cummins in February 1985, and it confirmed the viability of the engine and vehicle combination.
The Block
The cast-iron engine block used a linerless design that had several important engineering functions. The block held an integrally cast oil cooler cavity, water pump volute, oil pump cavity, and the camshaft didn't require press-in bearings.
Cylinder Head
The cast-iron cylinder head used a two-valve design with the intake and exhaust ports entering from opposite sides (crossflow). Helical intake ports were used to achieve the high-swirl requirements, and the intake manifold was cast integrally with the head. This reduced cost and provided a smooth transition at the critical entrance to the intake ports. Exhaust ports were exposed to as little water jacket area as possible to increase the available energy to the turbocharger and minimize heat rejection into the cooling system.
The cast-iron cylinder head featured induction-hardened valve seats (Rockwell C-50) to avoid the need for pressed-in seats without compromising mechanical durability. This also provided a cost reduction over traditional inserts. The valveguides were also machined in the parent material of the cylinder head. Six bolts per cylinder were used to attach the head to the block, two of which were shared by adjacent cylinders. One bolt per cylinder also served to clamp the rocker-lever assembly to the cylinder head.
Valves
Exhaust and intake valve rocker arms were made of ductile iron, classified as SAE D5506, and operated without bushings on a simple shaft that was pressed into a unique powdered-metal support. This support provided the oil-feed passages, attachment holes, location dowel, and a square protrusion that located the rocker cover without the need for additional machining.
Camshaft
Mushroom-type, chilled iron tappets operated the valves from the camshaft motion through pushrod tubes (the camshaft was also chilled iron). Die-cast aluminum rocker covers were chosen for cost and structural reasons. This required extensive analysis of the cover to ensure even load distribution to the gasket surface.