Issue link: https://read.dmtmag.com/i/78449
A LEGACY LIVES ON (Continued from Page 41) The fast throttle response and the extra boost from the turbo- compounding mean the engine builds torque far faster than com- petitive power. This is great for accelerating to speed on on-ramps for safe merging. It is also very use- ful when you need an extra boost to maintain momentum for short, sharp rises at freeway intersections, overpasses and such. It makes the Detroit engine feel much "bigger" and torquier than its rating suggests. For the longer climbs, the DD15 just gets down and grunts, offering no complaint when lugging down to 1,100 or even 1,050 rpms. Again, the additional boost from the turbo-compounding helps, converting waste heat from the exhaust into useful work at the flywheel. Multiple injection events greatly reduce diesel knock, and the stiff crankcase of the new engines helps reduce noise. What noise does escape is suitably quieted by the insu- lation package that comes with the EX. The tall final drive gear- ing meant some downshifting on the climb up Cajon and then across the Pearblossom Highway on the two-lane sections, but the easy-shifting 13-speed made it simple. In fact, the shift tower execution on the 4900 made it easy to select gears and a short throw to pick up each gear. The combination of the compounding and the tall gearing contributes to fuel efficiency, where the DD engines have been proving themselves in the post-2010 emissions environment. For this drive, continuous readings from the DataStar display showed fuel economy exceeding 7 miles per gallon, despite the big cab and rela- tively uncompromising spec of external air filters and cab-mounted exhaust. Contributing Editor St eve St omotive and related fields for more than 30 years. cover t 72 | Overdrive | September 2012 urgess has ed trucking, au- Text INFO to 50298 or visit ovdinfo.com