Grandi Motori Trieste

Grandi Motori Trieste

Grandi Motori Trieste (GMT) produced a wide range of medium-speed diesel engines over several decades. The company was founded in the late 1960s to combine the diesel engine expertise and resources of Fiat, Ansaldo, and CRDA, with the goal of streamlining Italy’s engine-building industry. Later, GMT became part of Fincantieri’s state-owned diesel engine division, and in 1997 it was acquired by Wärtsilä Corporation. Following the acquisition, GMT’s own engine designs were gradually phased out.

The company’s last major development, the A55 series, represented the final evolution of a 550 mm bore engine originally designed and built in Turin by Fiat Grandi Motori in the early 1970s. The first model, the A550, had a 590 mm stroke and produced 880 kW per cylinder. This was later upgraded to the B550, which delivered 1080 kW per cylinder at 450 rpm.

In 1986, GMT introduced the BL550, which kept the same bore and speed but featured a longer 630 mm stroke. This upgrade provided 10% more power and improved fuel efficiency, even when running on low-grade fuel. The new rating—1213 kW per cylinder—was achieved through a modest rise in mean effective pressure (from 20.6 to 21.6 bar) and an increase in mean piston speed (from 8.85 to 9.45 m/s).

To handle the higher mechanical and thermal stresses, GMT redesigned certain combustion chamber components and running gear. However, the in-line engines still used separate nodular cast iron frames and bedplates. In contrast, the eight- and nine-cylinder models adopted monobloc castings for the bedplate and frame, secured with tie-rods. The V-type engines featured a welded steel bedplate paired with a special cast iron frame, eliminating the need for tie-rods and instead using stud bolts for assembly.