Prevost operators report smoother performance and improved economy
By David Hubbard
The Volvo D13 diesel engine represents a significant step in fuel efficiency, emissions compliance and driver convenience for North American motorcoach operators. Built on the existing 2007 platform and available in 435- and 500-horsepower models, the EPA 2010 Volvo D13 features the addition of advanced Selective Catalytic Reduction (SCR) system, which the company says maintains engine power and performance without the need for active regenerations.
Prevost first introduced the Volvo D13 in 2008 as an alternative engine on Prevost and Volvo coaches. The company has since extended its availability to other OEMs as an engine option.
“The choice of the D13 sends a strong statement to the industry that Prevost Car is clearly a part of Volvo,” says Prevost President and CEO Gaetan Bolduc. “This is step one in our systematic changeover to a complete Volvo powertrain.”
With its variable geometry turbo, the claim is the D13 delivers excellent low-end torque and responsiveness with minimal noise and vibration. Volvo also says this engine delivers 5 percent better fuel efficiency than the previous EPA 2007 engines, which is the best fuel economy of any 13-liter coach engine on the market.
The D13 works with I-Shift transmission and I-VEB engine brake on Prevost and
Charter Bus Lines, Vancouver, British Columbia, took delivery in May on eight 2011 H3-45 coaches equipped with the Volvo D13 coupled to Allison transmissions. According to Wayne Eggen, Charter’s maintenance director, the D13 had few problems in the electrical system. Eggen says they were easily resolved and he has not had to contend with any other issues since.
“The minor glitch we ran into was no fault of the engine or ours,” he says. “The day we received the coaches a driver for the drive-away delivery service had filled one of the units with gasoline on his last stop before bringing it into the yard. While he made it to the yard, the engine conked out barely a quarter-mile down the road on our first test run. The engine survived. We just emptied the gasoline and refueled with diesel.”
Eggen says to preserve the warranty they had to return the coach to Prevost for replacement of the rods, rod bearings and injectors. The insurance company for the drive-away service got the bill.
This accident not withstanding, Charter Bus Lines gives the D13 high marks. The drivers responded positively on the quiet, smooth running performance, and Eggen says his company is seeing improved fuel efficiencies.
Operating in British Columbia, Eggen says his coaches essentially go through the torture test in the course of normal operation.
“Driving to and from Vancouver everything is either climbing or dropping,” he says. “We take these new coaches primarily on the run through the Canadian Rockies to Jasper Park and Banff Springs. There are several long steep grades such as the 12-percent grade for 13 miles around Duffey Lake along the Coquihalla Highway.”
He says the B500 jake brakes work well with no complaints, although the drivers did comment on a slight delay. Eggen adds that this was not a problem once they caught on to the new feel and what they needed to do.
Volvo attributes the reputation for a smooth, quiet operation of the D13 to the camshaft damper, which absorbs camshaft torsionals induced by the ultra-high fuel injection pressure. Additionally, as a member of the engine gear train, the large mass of the flywheel absorbs inputs from the other gears for a smoother operating engine and extended component reliability and life.
Adirondack Trailways, Hurley, NY, took delivery in June on 10 new 2012 H3-45s equipped with the 2010 Volvo D13 engine. The coaches have been running line-haul service on scheduled routes throughout the state of New York. James Morra, superintendent of maintenance, says the company has already seen as much as a 20 percent improvement in fuel economy.
“Our drivers were a little nervous over the power that might be lost, with the rumors they had heard about the potential effects of SCR, the addition of urea and DEF filters,” says Morra. “Once they got behind the wheel all doubts disappeared and they have no complaint about the power of this engine.”
Adirondack opted for the proprietary I-Shift transmission primarily for the choice of operation modes, performance or regular, which allows the drivers to adjust the shifting speed to their personal driving style and shifting preferences.
Volvo I-Shift is a 12-speed, two-pedal lightweight automated manual transmission (AMT) that integrates seamlessly with Volvo engines. The I-Shift transmission management system employs a next-generation microprocessor that improves drivability, safety and fuel efficiency. The I-Shift can instantly predict and select the most efficient utilization of the engine. In other words it knows when and where a shift is most beneficial. Volvo says it allows every driver to shift smoothly, putting less stress on the driveline and tires, which can extend the useful life of the driveline.
“Our drivers commented immediately on its smooth handling,” says Morra. “Regardless of experience, each driver can become more fuel efficient using the I-shift.”
The Adirondack Trailways H3-45s also incorporate Eco-Roll, another energy management feature that automatically disengages the engine when the vehicle is in top gear on a long, slight downgrade that requires no engine torque input. It reengages the engine when the speed reaches the engine brake set speed for the cruise control.
Morra says he is particularly impressed with the diagnostic software package that comes with the Volvo D13.
“This system encompasses all the other components that relate to the engine in some way, making it very thorough and complete.”
He says this makes the task of troubleshooting much easier.
“We haven’t had to do any troubleshooting, but we checked it out for when we do,” says Morra. “Our technicians really appreciate this aspect of the package. They can find the location of the components, know what they look like and read the necessary steps to resolve any problem. No one is left in the dark.”
Inside the Volvo D13
A stiff connecting rod of superior strength with wide journals and four-bolt attachment is at the heart of the power cylinder that features a rifle-drilled oil passage for pressurized lubrication of the piston pin. For maximum strength under high temperatures the oil-cooled piston utilizes a one-piece monotherm design. The top piston ring uses a proprietary PVD coating process, which when mated with the plateau-honed cylinder liners provides excellent oil control and minimizes bore wear.
Engine Management System
The engine management system (EMS) is located on the cold side of the engine in which fuel passes around the EMS to cool the unit. The EMS controls the centrally located unit injector driven from the cam. Ultra-high fuel injection pressure as high as 35,000 psi ensures efficient injection, atomization and combustion, striking a balance between fuel economy, performance and emissions control.
Exhaust gas recirculation
The unique vertical installation of the SCR and DPF system with rooftop diffuser mount produces less heat in the engine compartment, reducing exhaust peak temperature by 50 percent at six inches and prevents water from infiltrating the exhaust line. It also provides easier accessibility for safer maintenance. Volvo says this vertical configuration better protects the DPF and SCR components and sensors from damaging dirt, dust and moisture. BR