Peak torque: 1,500
Axle ratio: 4:17
Top gear ratio .74
Rpm limit: 1,800
Additional pounds: 90-100
Read how other engines performed in Overdrive‘s test drives.
When I told Stuart Childers about cooled exhaust gas recirculation, as we stood in a crowded rest area, he asked one question: “How does it pull?”
Childers, a driver for Hartford Trucking of Hartford, Kan., drives a 9900 series International with a Cummins 550 N14. He pulls plenty of heavy stuff on his dropdeck, and his concern with the performance of the new, cleaner burning engines echoes the thoughts of most drivers. Owner-operator concerns go beyond that into engine lifespans, maintenance intervals and costs.
At Mack, the same issues are paramount. In testing for five years, Mack’s EGR engines have been run in conditions far exceeding the 350-mile drive I took. But the long, steep grades I drove out of Allentown, Pa., were a good proving ground for pulling power and overall performance.
Steve Ginter, marketing vocational manager at Mack, says the C-EGR was designed for over-the-road applications in which speed, load and other operational factors are relatively constant. Mack has developed another technology, internal exhaust gas recirculation, for its vocational engines. I-EGR allows a portion of exhaust gases to remain in the cylinders from one combustion cycle to another, which provides a consistent level of emissions benefits and performance for vocational environments.
Neal Biser, Mack’s 29-year veteran lab tech, and I climbed into the CH 427 one morning to make the climb out of the Keystone’s eastern valleys and into the high, near-wilderness of the I-80 corridor. I pulled through a long, uphill ramp onto U.S. 33, having easily toted the 78,000 pounds we grossed through city streets with no shortage of low-end torque. There is plenty of torque straight through the power band.
“The torque rating for the 427-hp engine is 1,560 pounds-feet at 1,300 rpm, or about 11 percent over Mack’s E7 427,” Ginter says. “The 427 peaked at 1,200 rpm.” This means torque is felt more quickly. Throttle response is also very quick, thanks to the turbo boost coming from the new variable geometry turbo, Biser says. The turbo responds within 200 to 300 rpm rather than 400 to 500.
The turbo can fool a driver not used to its unusually quiet operation. There is none of the typical turbo air-sucking sound to make a driver think he is going fast. Instead there is a high-pitched whistle of significantly fewer decibels that spools up and down as the engine’s computer feeds data to the turbo. The electronic control module senses fuel needs, air intake and other factors along with the engine’s new requirement to recirculate highly specific amounts of exhaust.
The spooling sound seems unconnected to the driver’s throttle use because the turbo is responding to many different commands. But when I depressed the throttle, a faint rush of air could be heard behind the whistle – the only indication the turbo was gulping air in response to driver and engine demands. Drivers not used to these new sounds might easily mistake some of them for charge air cooler leaks.
A more noticeable feature of the variable turbo is that it tends to pull rpm down a little faster between shifts. But pulling the grades up U.S. 33, I was able to shift the Fuller 10-speed quite smoothly, perhaps a little more smoothly as a result.
Even with the extra engine weight, there is no overheating; oil temperature rises no more than normal. While under-hood temperatures have increased slightly, comfort was not affected.
“Oil drain intervals will stay the same, at 50,000 miles,” Ginter added. Thus the major difference is an increase in oil capacity of eight quarts, bringing the total in the pan to 40 quarts.
“Engine life is expected to be 1 million miles,” which is the same as current engines, says Don Brugger, project manager.