Patriot Coal Tags MTU Series 4000 Engine for Heaviest Loads in Repower of Komatsu 730E Overburden Truck

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Mining company switches to cleaner and more efficient engines for its fleet of mine haul trucks. The MTU Tier 2, Series 4000 12-cylinder engine delivers up to 20 percent better fuel economy.

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When it came time to repower one of the powerful Komatsu 730-E haul trucks, [Patriot Coal] decided to use the new MTU Series 4000 Tier 2 engine.

At a surface coal mine operated by Patriot Coal, the job of removing the tons of rock overburden is reserved for the most powerful haul trucks in the company’s fleet — the beefy diesel-electric Komatsu 730-Es. Many of the coal mines in this part of Appalachia are so-called “mountaintop” mines where the top of the mountain is literally removed to expose the seam of coal. To reduce fuel expenses and get longer engine life, Patriot Coal has been replacing the haul truck’s original-equipment Tier 1 engines with powerful and efficient MTU Series 4000 Tier 2 engines from Western Branch Diesel in Charleston, WV.

“Patriot Coal already had successful experience with MTU Series 4000 Tier 1 engines in 16 of their Komatsu 830 haul trucks,” says Curtis Bartlett of Western Branch Diesel, the region’s MTU distributor. “So, when it came time to repower one of the powerful Komatsu 730-E haul trucks, the company decided to use the new MTU Series 4000 Tier 2 engine. In addition to having the objectives of lower emissions, longer engine life and better fuel economy, Patriot wanted to standardize its fleet to reduce costs associated with parts and maintenance.”

More compact and powerful engine

The original engine power supplied in the Komatsu 730 was from a different manufacturer, had 16 cylinders and produced 2,000 hp. The MTU Series 4000 engine that was installed is capable of producing 2,250 hp with only 12 cylinders. MTU’s improvements to the Series 4000 achieved EPA Tier 2 emissions compliance by cutting nitrogen oxides and particulate emissions in half, while creating an engine with significantly higher power density, according to Bartlett.

“The MTU Series 4000 Tier 2 engine has a higher specific horsepower than the original-equipment engine,” says Bartlett, “meaning that each cylinder generates more power per cubic inch of displacement.” The higher output is due to a combination of improvements that include second-generation common-rail fuel injection, advanced electronic engine controls and more precise fuel metering for improved combustion compared to Tier 1 engines.

Big fuel savings

In addition to its compact size and higher power output, the Tier 2 Series 4000 12-cylinder engine delivers up to 20 percent better fuel economy, according to Bartlett. “The original 16-cylinder engine consumed 34.8 gallons per hour, and the MTU 12-cylinder engine consumes only 26.4 gallons per hour. That’s about 20 percent better fuel economy. Since these Tier 1-engine trucks burn about 80,000 gallons of fuel per year, the MTU Tier 2 engine is saving 16,000 gallons a year. At $3 per gallon, the savings can really add up,” Bartlett comments.

While the MTU 12-cylinder engine can produce 2,250 hp, the existing General Electric traction alternator and electronics in the haul truck are designed and limited to 2,000 hp. With this lower power requirement, MTU was able to limit the output of the new engine to 2,000 hp by simply installing a lower power calibration. This promotes longevity because the engine is operating at less than full power. Bartlett estimates the life of the new MTU Tier 2 engine to be at least 30,000 hours before an engine overhaul is required, or the truck is rebuilt.

About MTU

MTU Detroit Diesel, Inc. is the North American regional headquarters of MTU Friedrichshafen GmbH, one of the world’s most important providers of diesel engines and drive and propulsion systems for ships, heavy-duty land and rail vehicles, and distributed energy. It offers a complete line of power solutions from 30 to 12,200 bhp (20 to 9,100 kW) for applications in the marine, rail, power generation, oil and gas, agriculture, mining, construction and industrial, and defense markets. MTU Detroit Diesel, Inc. is the sales and after-sales organization of the Tognum Group in North America.


With its two business units, Engines and Onsite Energy & Components, the Tognum Group is one of the world’s leading suppliers of engines, propulsion systems and distributed energy systems. These products are based on diesel engines with up to 9,100 kilowatts (kW) power output, gas engines up to 2,150 kW, stationary fuel cells up to 345 kW and gas turbines up to 45,000 kW.

The product portfolio of the Engines business unit comprises MTU engines and propulsion systems for ships, for heavy land, rail and defense vehicles and for the oil and gas industry. The portfolio of the Onsite Energy & Components business unit includes distributed energy systems of the brand MTU Onsite Energy and fuel-injection systems from L’Orange. The energy systems comprise diesel engines for emergency standby power, prime power and continuous power, as well as cogeneration power plants based on gas engines, fuel cells and gas turbines that generate both power and heat.

In 2009, Tognum generated revenue of €2.5 billion and employs more than 8,700 people. Tognum has a global manufacturing, distribution and service structure with 25 fully consolidated companies, more than 140 sales partners and over 500 authorized dealerships at approximately 1,200 locations. The shares of Tognum AG (ISIN: DE000A0N4P43) have been stock-exchange listed since 2007 and are included in the MDAX.


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