Most truck engine makers are being decidedly cagey about the next technological steps they’ll be taking to meet Phase 2 of the greenhouse gas (GHG) fuel economy regulations recently outlined by the federal government.
A good example can be found in the statement offered by Paccar Corp., the parent company of U.S. truck makers Peterbilt Motors and Kenworth Truck, to Fleet Owner when asked about how it plans to bring its MX line of engines into compliance: “Paccar successfully achieved the greenhouse gas Phase 1 regulations, which were good for the environment and our customers, [and] we are evaluating the greenhouse gas Phase 2 proposal. We look forward to working with the Environmental Protection Agency and National Highway Traffic Safety Administration during the comment period and to developing strategies to meet the new regulations.”
Doesn’t provide much to go on, does it?
The future of fuel economy
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Yet one reason manufacturers may be holding their GHG cards close to their vest is due to the plethora of technological options currently on the table, explains Allen Schaeffer, executive director of the Diesel Technology Forum.
“They are really going to start focusing on areas of the engine that have not been significantly addressed to date in terms of energy losses,” he says.
“We’re also probably going to see a divergence in [GHG] solutions based on operating parameters,” Schaeffer adds. “More transient operations such as urban stop-and-go driving may see a different set of solutions compared to engines in steady-state highway driving operation.”
On top of that, two major engine “locales” will be the main focus for engineers, he points out, i.e., energy/heat loss through the exhaust system and energy/heat loss or “rejected” through the engine’s plumbing.
The energy lost just through those two areas represents 24% and 26%, respectively, of the engine’s total energy footprint, Schaeffer stresses.
“Those are very big boxes, and that’s why many believe big opportunities still remain to improve diesel [truck engine] fuel economy,” he says.
Specific tactics that may be deployed to address those areas include:
◗ Reducing parasitic loads on the engine. Right now, components such as water pumps are tied to the engine and must operate at the same speed because of that connection. Shifting to electrical power for water pumps, enabling them to work independently of engine speed to provide coolant flow as needed, allows the engine to be more efficient.
◗ More turbocharging. The EcoBoost engine platform used by Ford Motor, where twin turbochargers give a V6 engine the power of a V8 on an as-needed basis, is being viewed as a blueprint as a way to help shrink the overall size of truck engines without sacrificing performance and power. There are a lot of fuel efficiency ripple effects to downsizing an engine, too, Schaeffer notes. “A smaller engine requires a smaller engine fan, lowers its overall weight, etc.,” he says.
◗ Waste heat recovery. Recapturing energy lost through the exhaust system via a secondary coolant system is a possibility but would add another system to the vehicle, potentially increasing costs while adding extra components and maintenance.
◗ More precise fuel injection/combustion. In many ways, Schaeffer says, modern computing power is still being brought to bear on how to more precisely—and efficiently—control the fuel combustion process within the engine. “This is where that divergence between steady-state and transient engine operations will be felt the most, allowing combustion to be optimized specifically to the type of work expected of a truck engine,” he explains.
◗ Start/stop engine operation. In urban stop-and-go environments, shutting the engine down at stop lights and in heavy traffic congestion, then quickly restarting it when power is needed is another light vehicle technology making its way to the heavy side of the market to boost fuel savings. “It takes some getting used to, but it breaks away from the conventional operating mode of an engine and it saves fuel,” Schaeffer points out.
He adds that many of the fuel economy gains needed to meet Phase 2 fuel efficiency targets may occur in piecemeal fashion. Individual changes resulting in 2% or 3% efficiency gains will add up to the larger total numbers required to meet the ambitious GHG goals.
“It’s stringing together a series of small gains that will be critical. It will be an additive process that achieves the fuel economy targets being established by the Phase 2 rules,” Schaeffer notes.
