Because the engine uses SCR, it requires diesel exhaust fluid, but the payoff is worth the cost of DEF, Thompson says. “My pipes are the same color as they were when the truck was new,” he says. “Even though it’s an extra cost, it has its benefits. In this day and age, everybody has to be ‘clean, clean, clean.’ I think this engine is a pretty good option.”
Putting the focus on fuel economy
In addition to turning the MaxiCruise MP8 into an SCR engine, last year Mack also developed another engine, the Econodyne. It’s built “strictly as a fuel-economy engine,” says Mack’s David McKenna.
It’s available in the same horsepower ratings as the MaxiCruise, but uses a more conventional torque curve through the engine’s rpm range.
The engine’s attempts at improving fuel economy stem from its ability to offer an extra 200 lb.-ft. of torque, allowing drivers to stay in top gear longer. If the driver spends four seconds or more at full throttle at or below 1,300 rpm, the extra torque shows up.
“It’s been proved empirically the longer you can keep a truck in top gear, the better fuel economy is going to be,” McKenna says. “This engine sort of rewards drivers for operating it the way it should be operated.”
Configuration: Inline six-cylinder
Displacement: 13 liters (780 cu. in.)
Bore and stroke: 5.16 x 6.22 in.
Governed speed: 1,800-2,100 rpm
Horsepower ratings: 415, 445, 505
Lubrication system capacity: 33 qt.
Torque ratings: 1,460 to 1,760 lb.-ft.