EGR Test Drive: Detroit Deisel
Series 60 430
Peak torque: 1,200
Axle ratio: 3:9
Top gear ratio .74
Rpm limit: 2,100
Additional pounds: 170
Read how other engines performed in Overdrive‘s test drives.
I left Vehicle Testing Services, a San Antonio, Texas, facility where Detroit Diesel is testing its VNT EGR engines, in a Century Class Freightliner. Chuck Blake, Detroit’s application engineer, and Jason Grobbel, who runs Detroit’s operation at VTS, helped me through busy interstates, where the 12.7-liter 430-hp Series 60 performed well. This engine has an almost aggressive throttle response. The nearly silent variable-nozzle turbo punched through the rpm range quickly, pulling our 69,000 pound gross weight quite well in ninth and tenth.
Farther out in the rolling hill country west of San Antonio, Grobbel confirmed my impression. “That quick throttle response gives enough boost to help out a lot on these low rollers,” he says. And when I stopped just west of Kerrville on the last outbound grade, the responsiveness of the turbo was even more helpful getting up to speed on the steep ramp and into traffic.
By the time I reached the top I had climbed to eighth and coasted over the crest without undue water or oil temp rise. Grobbel says Detroit expects oil temps to stay below 260 degrees. My gauge read about 240 on the most significant pulls.
“Exhaust temperatures will remain the same even though combustion temps are lower,” says Blake. “Engine temps and under-hood temps will rise, so cooling is very important. Cooling system maintenance is equally important.” Sour smells and a brown coolant will indicate that coolant requires attention, Blake says. Today’s coolants will be standard; no special coolants will be required, he says.
Just west of Kerrville, where we turned around, I changed to the Freightliner FLD that had followed us to test a Series 60 rated at 500 hp and 1,650 pounds-feet of torque. Loaded to 78,000 pounds, we flattened all the grades headed east. The 7 percent grades took more out of the 430 that trailed us, but the difference was no more than a drop of one gear or perhaps a loss of more rpm, though not enough of a loss to necessitate grabbing a gear. The 430 stayed right behind me all the way back to San Antonio.
The new turbo gives enough quick throttle response to make the time-honored technique of getting a run for the next grade a more effective maneuver. Downhill runs were improved, too, because the increased back-pressure required by EGR to push the hot exhaust back through the recirculation system also makes it possible to boost engine brake performance. Intake manifold pressures now have the ability to outrun boost gauges. Blake believes pyrometers can play a bigger role because by indicating significant changes in engine temperature, they will allow drivers to adjust throttle pressure accordingly.
“Variable speed turbos have been around a long time, but price was prohibitive,” says Phil Rimnac, manager of the Series 60 Advanced Product program. “EGR made it necessary to use the power of the variable turbo.” Forcing the correct amounts of exhaust back into the charge air cooler stream requires varying the speed of the turbo and creating more back-pressure. That’s needed to shoot inert gases into the cylinders where the charge air and the EGR cooler pipe meet and shove cooled exhaust into the air stream.
This pipe’s position across the top of the engine makes it a tempting handhold for a driver climbing with the hood open to wash the windshield. Blake cautions against that: “Despite its name, the pipe is not cool. Using it as a handhold will get you burned.”
The cooler and EGR valve, on the passenger side, are also clearly visible. But Detroit’s technology for activating the valve and starting the EGR process is hidden. One of two air-driven variable-pressure output devices gets a signal from the electronic control module to open and close this valve, while the turbo is activated by the second VPOD.
Even with the new hardware, the Series 60 EGR engines now weigh 30 to 40 pounds less. Grobbel attributes that to a pared-down gear case now capped with aluminum.
As for maintenance intervals, Blake says, “The no-brainer maintenance level of 15,000 miles remains standard. But Detroit is hoping to raise this basic level to 30,000 before October ’02.” Fleet preventive maintenance is expected to remain at the now-standard level of 25,000 to 30,000 miles, he says.