A new combination of engine and chassis has resulted in the most efficient heavy truck ever to carry the Kenworth nameplate.
Meeting the latest regulatory requirements for reduced exhaust emissions while boosting the mileage for heavy trucks has been a challenge for manufacturers.
Kent Smith, engineering manager for Kenworth Truck Company in Kirkland, Washington, helped release that company’s latest T series machine, and the first to carry a Paccar engine.
“We have had a long relationship with Cat, and still offer Cummins as an option, but we are very happy to have the (Paccar) MX engine in the new T700.”
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Without Cat as an engine partner, selection of power plants was affected. Putting a Paccar engine in the truck had been in testing for the past six years.
Paccar is the international parent company of Kenworth, Peterbilt, DAF and Leyland truck brands. The company’s engines are also found in large buses and DAF and Leyland brand trucks in other parts of the world.
“They had a lot of experience with this engine in buses, putting on millions of miles. It’s a solid design,” said Smith.
The compacted graphite iron used in the block and head is lighter and stronger than grey iron, the traditional engine block material found in most industrial, agricultural and transport engines.
Rolls Royce and Cat use some in engine production but DAF began working with it in 1997 and placing it in commercial trucks in 2001. The MX engines in the new Kenworth were introduced in 2002, with a major redesign in 2005.
It is a high torque, low speed 12.9 litre engine that can be set to produce between 380 and 485 horsepower.
Weight reductions in the block extend into features like a counter-weightless crankshaft and an aluminum oil pan stiffener and noise dampener that substitutes a lighter metal insert in place of heavy steel gussets.
The thermostat and oil cooler on the Paccar engine are mounted directly into the block without external lines, reducing components to extend service intervals.
Rather than just grouping engine wiring in a plastic harness, the wiring is cast into a moderately flexible, poly housing that is wear and heat resistant and clipped to the engine for easy removal and replacement.
One of the other features of the engine is the use of fractured caps on the rods and main bearings. Connecting rods and main bearing carriers, as a part of the block, are cast whole and then machined. A laser scribes a line into each one to provide direction for a break point, similar to etching glass. Then the caps are snapped off. The result is a rough but perfectly matched set of mating surfaces that resist twisting and shearing.
“It results in greater strength from lower weight materials,” said Smith.
A combination of selective catalytic reduction and the use of filtration through an exhaust gas recirculation process allowed the truck to meet emission goals. This combination is expected to be the long-term solution for most off-road engines in the future and is widely adopted in on-road diesel applications.
The result is that diesel exhaust fluid, a urea and water mix, is housed in a heated tank, available in several sizes, on the T700 trucks.
The Paccar engine is married to the new chassis that has been stripped of weight and made more aerodynamic, with a combination of plastics and metal to create a cab that is better sealed and more slippery in the air than its predecessors.
“The sleeper is completely integrated into the cab, creating a lot more room and providing a quieter and more comfortable space for the operator,” he said.
Richard Riel of Custom Truck Sales in Saskatoon said new trucks are significantly more fuel efficient. For owners looking to use them for grain, fertilizer and bulk hauling with some supplementary winter work, the mileage issue adds up quickly.
“It wouldn’t matter as much if you think that fuel prices are going to go down or you won’t need to be running more miles with your truck in the future,” he said.
“When you order one of these, it is set up at the factory to get you the right combination engine and gearing for low speed power to lift a truck on soft ground or high mileage on pavement or a compromise that gets you some of each.”
Other Paccar engines are showing up in the medium duty truck lines, including 6.7 and 8.3 litre offerings that range from 200 to 330 h.p.
