The Power of Giants

In the off-highway equipment world, man is often walking among mobile giants. But, there are self-propelled monoliths that dwarf even the common excavators and tractors. Driving these massive machines are high-horsepower engines capable of power outputs upwards of 500 hp.

These 500+ hp engines span across off-highway industries (construction, mining, military, agriculture, etc.) and are seen in heavy-duty on-highway trucks. “Customers in these applications have a need for high reliability and a high peak power at critical points during their work,” says Clint Schroer, off-highway communications, Cummins Inc., Columbus, IN.

New Holland’s Guinness World Record-setting CR9090 rotary combine (above) features a powerful turbo compound engine at 544 hp at rated engine speed with a maximum harvest power of 591 hp available.

The turbo compound technology allows for increased engine efficiency with a 5% fuel savings over similar horsepower engines. The turbo compound system uses a second turbine, downstream of the first, to recover energy from the engine exhaust gases that would otherwise be lost. The larger fuel tank at 306 gallons (1,160 liters) allows for longer work time and is fully compliant with 100% biodiesel.

Why one engine?
In an article by Chad Elmore in OEM Off-Highway’s March 2008 issue, “It’s not what you think,” the value and efficiencies offered by installing two diesel engines are explored. While there are applications where utilizing the power of two engines is best, there are benefits to employing one massive powerhouse of an engine.

Schroer comments, “One engine is often more fuel efficient when integrated fully into the machine. The response and power from dual engines could produce the same power if installed correctly. Some customers don’t like servicing dual engines, and sometimes dual engines cause some installation complexity with dual transmissions and so on.”

In agriculture specifically, implements such as air seeders and tillage tools are growing in size to satisfy the demand for better efficiency on growing farms. “This growth continues to demand high horsepower tractors and the only practical and efficient way to do this is with one powerful engine,” explains Cat’s Industrial Engine team: Greg Flo, Caterpillar account manager for AGCO; and Brent Salverson, product definition marketing manager.

“Multiple engines in a tractor application would create integration challenges for the tractor manufacturer and increase the number of parts in the engine offering due to duplication, as well as increase overall machine length, width or both.

“Also, large engines are inherently more efficient—that is, they use less fuel per unit of work produced at higher loads—than smaller ones due to higher turbocharger efficiencies and relatively large inlet and exhaust ports which improve breathing and reduce restriction,” says the Cat Industrial Engine team.

“The more sources of power you have, the more opportunity of energy loss you have. For example, if you have three engines generating a total of 2,000 hp versus one engine generating 2,000 hp, you have to add up the losses of those three engines. When you add that up you may have to actually generate more power out of the three engines to get the 2,000 hp than you would out of a single engine,” explains Scott Woodruff, director of industrial sales and engineering, MTU Detroit Diesel Inc., Detroit, MI.

One engine also simplifies the control system complexity when integrating into the CAN bus system and other electronics on the machine. When you have multiple engines, the control complexity is much higher, and you have more opportunity for software problems and logic issues.