The DD15 also has a turbocompounding turbine in place of the variable geometry used on most engines’ turbochargers. This device returns exhaust energy to the crankshaft through a
geartrain, and builds the backpressure needed to make the EGR system work in a less wasteful manner than a variable geometry turbo.
Paccar’s Treasure says, “The DEF will be injected as the exhaust flows through a mixing tube or pipe. This will ensure a complete mixing of the DEF in the exhaust gas and will occur just before the exhaust enters the SCR catalyst.”
Where will the other components be located?
The DEF tank will always be near the left-hand fuel tank for convenient refilling when refueling.
Morelli says most Daimler-built trucks will have everything located under the right-hand cab entry steps, a typical location for all brands. But there will be other, very different Daimler options, too. McKenna says, “The pump that supplies the DEF will continue to run after the engine is shut off, returning unused DEF back to the tank to prevent supply line freeze-ups.”
While all new technologies usually start with minor problems, the U.S. market has the advantage that SCR has been used in Europe for years. McKenna says, “There has been nothing in the way of negative performance issues, whether we are referring to system robustness or consistency of emission and fuel economy performance.”
In Europe, Cummins has more than 200,000 SCR systems in service. Paccar has more than 100,000. Company officials say this experience should minimize major headaches a year from now when SCR engines hit the road here.
Keeping an eye on that other tank
Truck makers using SCR engines plan to have a dash gauge and warning system to ensure drivers don’t let the diesel exhaust fluid level drop too low. Your engine would never shut down due to lack of DEF, but neither would you want to test the limits too much.
David McKenna of Mack Trucks gives a preview of Mack’s progressive warning system:
“When the DEF level drops to around 20 percent remaining volume, a dash indicator lamp will inform the driver that a DEF fill up is in the future. At something around 5 percent to 10 percent, an audible tone will sound that informs the driver that there is now a minimum reserve of DEF remaining and a small engine de-rate may occur. What happens when the DEF runs out? The engine will go into a substantial de-rate and the road speed of the truck may be limited to 15 mph. At no time will the engine completely shut down and leave you stranded on the road.”
Finding DEF on the road should be no more difficult than finding a truck stop. Aggressive plans are under way to make DEF universally available at truck stops.
OOIDA, Navistar call for postponing deadline
The Owner-Operator Independent Drivers Association has called for a re-evaluation of the U.S. Environmental Protection Agency’s tougher 2010 heavy-duty engine emissions standards.
The call came after publication of a study conducted by NERA Economic Consulting that concluded the price of trucks employing 2010 technology would be significantly higher. Given the slowing economy, OOIDA says, this price premium will be an undue hardship on all parties. Navistar, which helped fund the NERA study, said it stands with OOIDA.
“When those new engines come out, they’re going to be more expensive,” says Navistar spokesman Roy Wiley. “Many of the truckers won’t be able to afford the 2010s.”
A gradual phase-out of 2007 emissions standards would be the goal of changing the Jan. 1, 2010 deadline, Wiley said.