How Diesel Locomotives Work

The Engine and Generator

The main engine in this locomotive is a General Motors EMD 710 series engine. The "710" means that each cylinder in this turbocharged, two-stroke, diesel V-12 has a displacement of 710 cubic inches (11.6 L). That's more than double the size of most of the biggest gasoline V-8 car engines -- and we're only talking about one of the 12 cylinders in this 3,200-hp engine.

So why two-stroke? Even though this engine is huge, if it operated on the four-stroke diesel cycle, like most smaller diesel engines do, it would only make about half the power. This is because with the two-stroke cycle, there are twice as many combustion events (which produce the power) per revolution. It turns out that the diesel two-stoke engine is really much more elegant and efficient than the two-stroke gasoline engine. See How Diesel Two-Stroke Engines Work for more details.

You might be thinking, if this engine is about 24 times the size of a big V-8 car engine, and uses a two-stroke instead of a four-stroke cycle, why does it only make about 10 times the power? The reason is that this engine is designed to produce 3,200 hp continuously, and it lasts for decades. If you continuously ran the engine in your car at full power, you'd be lucky if it lasted a week.

Here are some of the specifications of this engine:

  • Number of cylinders: 12
  • Compression ratio: 16:1
  • Displacement per cylinder: 11.6 L (710 in3)
  • Cylinder bore: 230 mm (9.2 inches)
  • Cylinder stroke: 279 mm (11.1 inches)
  • Full speed: 904 rpm
  • Normal idle speed: 269 rpm

This giant engine is hooked up to an equally impressive generator. It is about 6 feet (1.8 m) in diameter and weights about 17,700 pounds (8,029 kg). At peak power, this generator makes enough electricity to power a neighborhood of about 1,000 houses!

So where does all this power go? It goes into four, massive electric motors located in the trucks.