Engine Notebook: MTU-Detroit Diesel Series 4000, Tier 2

Say you have 300 or 400 tons of material to move every 30 minutes and you’ve got to do it more than two miles above sea level using an engine that must meet stringent emissions levels. It’s a tall order, and this spring MTU-Detroit Diesel introduced the Tier 2 Series 4000 to meet the challenge.

How big are these engines? If you’re proud of the power you get out of your five-liter pickup truck engine, note that each single cylinder in the new Series 4000 offers 4.8 liters of displacement. And each cylinder generates 188 horsepower/140 kilowatts. Multiply that times 12, 16 or 20 cylinders and you begin to get a sense of the scale of these engines. (See chart below for the details.)

While engines for most earthmoving machines with lower horsepower have transitioned to Tier 3 designs in the last few years, big engines like the Series 4000 are just now coming up on their Tier 2 phase. The goals are the same though, to meet the tighter emissions standards without compromising performance. What makes the new Series 4000 engines intriguing is that they show how much can be done when you mix proven basics (a pushrod design with the cylinders aligned in a V configuration) with new and sophisticated technologies including, advanced electronic engine control, new injection systems and water cooled turbochargers. In transitioning from Tier 1 to Tier 2, the company also increased displacement and upped the horsepower ratings over the previous designs.

Refining the fuel injection system was one of the keys for meeting these goals. “When the first generation of the Series 4000 engine was introduced in 1997, fuel injection pressure was contained within a common rail,” says Ran Archer, manager, mining sales. “The series 4000 Tier 2 engine also has a rail, but there is an additional fuel pressure reservoir integral to the injector. This places fuel pressure closer to the injection point, which minimizes pressure fluctuation caused by an adjacent fuel injection event. This injector reservoir improves metering accuracy and ultimately results in better fuel economy and lower emissions,” he says.

Series 4000 Tier 2 engines
Model 12 cylinder 16 cylinder 20 cylinder
HP (at 1,800 rpm) 2,250 3,000 3,750
Displacement (liters) 57.6 76.8 96

Because of the emissions restrictions there is some reduction in fuel economy compared to the Tier 1 engines, Archer says, but better injection control minimizes the loss and increases top-end power. The engine’s electronic control, called ADEC, comes with greater computational abilities. “The ADEC platform will serve us well for years to come and help us leverage opportunities to improve fuel economy, emissions control and engine diagnostics for cleaner diesel performance and lower operating cost,” Archer says.

Another design element new to the Series 4000 engine is a water-cooled turbo and exhaust manifold. By running coolant through the turbos and triple-wall exhaust manifold, the engineers reduced exhaust manifold surface temperatures from 1,256 degrees Fahrenheit (680 degrees Celsius) to below 392 degrees Fahrenheit (200 degrees Celsius). This serves primarily a safety benefit in that it reduces the risk of fire, but it also makes the engine quieter.

One of the toughest challenges big mining equipment faces is being able to operate at high altitudes without sacrificing power or performance. But by using proprietary turbochargers tuned for specific performance parameters, MTU-Detroit Diesel was able to maintain the rated horsepower output up to 12,139 feet (3,700 meters) using fuel-optimized calibration and 10,498 feet (3,200 meters) using emissions-optimized calibration. This enables them to boost productivity and lower cost per ton for equipment running in these oxygen-starved sites that previously restricted productivity.

To cut down on the service intervals, MTU-Detroit Diesel eliminated conventional oil filters and equipped the new Series 4000 with automatic oil filtration which is continuously self-cleaning, Archer says. The system consists of an oil strainer and two centrifuges. The centrifuges spin the oil at high speed throwing heavy soot and other contaminants to the outside of the filters and drawing the clean oil down from the center. Archer says the automatic oil filter system extends the filter maintenance interval for the new Series 4000 to 1,000 to 2,000 hours.