Train manufacturer CSX estimates that their fleet moves 1 ton (0.9 metric tons) of cargo an average of 492 miles (791 kilometers) per 1 gallon (4 liters) of fuel, making locomotives four times as efficient as moving goods on roadways. Why Diesel?ĭiesel engines are more efficient than gasoline engines, and when moving literal tons of freight or passengers, efficiency is paramount. The traction motors can produce adequate torque at any speed, from a full stop to 125 mph (200 kph), without needing to change gears. The generator sends electrical power to a traction motor at each axle, which powers the wheels. It would also have to provide power to four sets of wheels, which would add to the complexity.īy going with a hybrid setup, the main diesel engine can run at a constant speed, turning an electrical generator via driveshaft. With a speed range like this, a locomotive would need 20 or 30 gears to make it up to 110 mph.Ī gearbox like this would be huge (it would have to handle 4,200 horsepower), complicated and inefficient, and create a possible point of mechanical failure.
The large displacement diesel engine tops out at about 2,100 rpm, or lower. Diesel engines have a much slower operating speed than gasoline, and that goes double for the massive ones used in locomotives. The five-to-10-speed transmission on most cars allows them to go 110 mph (177 kph) or faster with an engine-speed range of 500 to 6,000 or higher rpm.
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