The Saab B engine was created in 1972 when SAAB bought Scania. It was completely built by Saab-Scania, at the Södertälje factory. The design was based on the Triumph Slant-4 engine, but with an increased engine displacement from 1.9 to 2.0 litres. This engine shared much with the original Triumph design, including bore centers and bearings, but was substantially redesigned. The redesign kept the unusual waterpump arrangement, which consisted of a cast aperture in the block, and the pump shaft with bearing, seals and impeller pressed into the aperture. The pump is driven by a jackshaft and helical gear. Later B engines used a fine tooth gear which is easily damaged and is a weak link in an otherwise very reliable engine.

In 1977, Saab added a turbocharger, creating one of the earliest turbocharged engines in volume production. This was placed in the Saab 99 Turbo model.

In 1981, Saab began lightening and redesigning the engine, creating the Saab H engine.