TMC issues scorecard on 2007 diesel engines

March 1, 2008
The Lead-off technical session of TMC's annual meeting was a panel discussion by several large fleets

The Lead-off technical session of TMC's annual meeting was a panel discussion by several large fleets of their experiences with 2007-emission compliant heavy duty diesel engines, compared to 2002 and 2004 emissions engines. Overall, these fleets found the engines to be more expensive to purchase, more costly to operate, and had considerably more downtime.

On the positive side, the fleets said the new 2007 diesels provide performance improvements.

“The trucks are hot rods and the drivers really want to drive them,” said Dan Umphress, managing director-maintenance solutions, FedEx Freight. “Drivers have enjoyed responsiveness of newer engines,” added Tom Newby, director-field maintenance, Old Dominion Freight Line.

The two were on the panel along with Steve Duley, vice president-purchasing equipment, Schneider National.

All three reported that their fleets had a steady improvement in engine performance and fuel economy through each emission standard. However, when engines are measured against pre-emission diesels, the 2002, 2004, and 2007 engines all cost sequentially more through each model year, particularly in terms of purchase price, maintenance, decreased fuel economy, and downtime.

Umphress, Newby, and Duley each concurred that along with training for service technicians on the 2007 emissions engines, education of drivers is required for their understanding of particulate trap operation and regeneration.

FedEx Freight

From FedEx Freight's experience with 2002 and 2004 emissions engines through early 2007, Umphress reported a $4,000 increase in vehicle acquisition cost. Fuel economy dropped about 3 percent. There was no change in maintenance schedules, but the fleet experienced high failures of new emissions components — turbochargers, EGR (exhaust gas recirculation) valves, coolers, sensors, etc.

The carrier's standard power unit is a 4×2 non-sleeper tractor that pulls two 28-foot trailers, grossing around 66,000 pounds.

With the 2007 emission compliant engines, there was a $7,000 increase in acquisition cost. Fuel economy remained at about 3 percent below pre-2002 and 2004 emissions engines.

Umphress said the emissions components on the 2007 engines have been much more reliable than 2002 and 2004 emissions engines. Nevertheless, maintenance schedule changes were required for the 2007 engine's coalescent crankcase filter and diesel particulate trap.

Drivers need training on the new 2007 engines, he said, especially with regard to the new exhaust emission systems' warning lamps and dash controls that vary by truck manufacturer.

Old Dominion Freight Line

Old Dominion Freight Line is running 7.2-liter EGR and 13-liter and 15-liter CGR (cooled gas recirculation) engines. Because of the extra weight of the engines, placement of the fifthwheel was moved back for weight distribution purposes and the gear ratios were changed.

“The torque curves on the 2007 compliant engines are basically the same as the pre-2007 engines, said the company's Newby. “The drivers love them because of the acceleration benefit.”

As for fuel mileage, pre-2007 13-liter engines average 6.7 to 6.9 miles per gallon; the 15-liters, 6.3 to 6.5 mpg. With the 2007-emission compliant diesels, all with less than 100,000 miles, the 13-liters average 6.4 to 6.8 mpg; the 15-liters, 5.9 to 6.1 mpg. Fleet speed is governed at 68 mph.

Newby said drivers are trained on the new 2007 engines and their emissions equipment. Decals explaining the exhaust aftertreatment system are installed in all trucks.

Technicians are trained on servicing the new engines. A special training module was designed specifically for this purpose.

Old Dominion Freight Line added specific 2007-emission engine PM checks to its preventive maintenance forms, “making the whole PM process more productive,” Newby noted.

Schneider National

Steve Duley of Schneider National said the new 2007 emission engines required a number of vehicle specification changes to accommodate the new engines. These included a larger, engine-mounted radiator; fan blade and fan shroud; different engine mounts and isolators; space for the aftertreatment devices; electrically controlled variable geometry turbo; crankcase vent coalescor; and a change in the type of transmission oil cooler. This resulted in a weight increase of 350 pounds.

With regards to vehicle service, he reported no change in the oil drain interval, and lowered oil consumption — approximately 7,000 miles per quart. The fleet has experienced up to a 2 percent loss in mpg due to regeneration of the diesel particulate traps.

Schneider National's frequency of repair on its 2007 emission engines is nearly five times that of the pre-2007 engines. Vehicle downtime has increased 20 percent and towing up 15 percent.

As for fuel economy with the emission engines compared to pre-emission models, the 2004s had a 4 percent loss in mpg; the 2007s a 5 percent loss.

The carrier's life-to-date gross maintenance costs (total maintenance less accidents and tires) for its 2004 EGR engines is 62.8 percent above pre-EGR models. The one-year gross maintenance costs for its 2007 emissions engines is 282% above pre-EGR engines.

In terms of the total cost of emission compliance since October 2002, Duley said Schneider National is paying 8.2 cents per mile, up from 6.7 cents per mile, over the six-year life of its tractors.

Like FedEx Freight, the carrier has also had numerous problems with the various components of the exhaust aftermarket system.

Schneider National has developed training on the 2007 emissions engines for drivers, technicians, and emergency maintenance (call center) personnel. The fleet also has cab decals in all its trucks that explain operation of the exhaust aftertreatment systems.