Peak torque: 1,550
Axle ratio: 3:73
Top gear ratio .74
Rpm limit: 1,900
Additional pounds: zero
Read how other engines performed in Overdrive‘s test drives.
What about Caterpillar?
I pulled the 435-hp VNM 64T day cab out of Volvo headquarters in Greensboro, N.C., grossing 70,000 pounds. I noticed that typical turbo sounds were lacking, replaced by a slight whistle as the turbo responded to driver and engine needs. As with other EGR engines, there was sometimes a disconnect between sound and expectation, the real indication of performance being throttle response and power through the rpm range.
Unlike other EGR engines, however, Volvo’s D12D was designed without changing the turbo. While the variable geometry turbo used by Volvo’s competitors provides the giant quantities of air for strong horsepower, the moving vanes in those systems lack the simplicity of the V-Pulse design.
“V-Pulse technology achieves EGR by harnessing naturally occurring engine pressure as a means to reintroduce up to 30 percent of the combustion byproduct back into the intake mixing chamber,” explains Volvo literature. Or as Volvo Sales Engineer John Moore puts it, “The only moving parts are a reed valve and two control valves. The cost of the turbo is lower with V-Pulse, and there is no training necessary for mechanics.”
The new turbo technologies make EGR engines quicker to meet horsepower needs than their higher-emission predecessors because the EGR system is controlled not only by driver actions but also by the engine’s computer. The turbo is ready to respond to throttle pressure much more quickly. The V-Pulse system spools up before a driver mashes his motor so that the engine is ready to perform much further down the rpm range. This gives the D12D excellent low-end torque.
I left Greensboro headed west toward Pilot Mountain and the infamous Fancy Gap grade. Driving in heavy traffic on I-77, I made frequent use of my left turn signal and was not disappointed. The strong passing power foreshadowed a relatively easy climb up the 7-mile, 6 percenter going north from Winston-Salem.
I crossed the Virginia line bound for Fort Chiswell, where I would do my flip. Having lunked the incline from the rest stop far into the Virginia highlands in many trucks, I expected to get into the granny and stay there. But I managed to maintain my gear, eventually shifting down and maintaining a steady 40 mph to the top, with no undue increase in water or oil temp.
The air conditioner kept me comfortable without taxing the engine on a grade where a lot of guys will shut down their cab coolers to keep engine temps stable. Volvo, like Mack, says integrating its own engines and trucks works best, giving systems such as cooling an advantage over competitors.
Fancy Gap gave ample opportunity to understand the power curve. Just when you think you’re at the top and starting down, you run up and down some valleys ending up in a different gear than the one you used to pull the fat part of the hill. In this case, the power band, which runs about 1,100 rpm to 1,900 rpm, proved itself strong.
I did not use the cruise at all, instead driving the truck like an owner-operator rather than like a fleet guy looking for a fuel bonus. That yielded a little more than 5 miles per gallon on the 109 miles to Chiswell and a little more than 6 on the way back.
Volvo has not increased oil capacity or changed drain intervals, so owner-operators face no new costs there. Nor has Volvo changed the ratings of its engines, which are expected to live to 1 million miles, says Mike Cantwell, product applications manager.