The 6x2s are coming...but when?: We’ve been hearing a lot over the past year about the advantages of 6x2 axle configurations, where power is supplied to only one drive axle, providing about 400 lbs of weight savings or fuel economy...
The 6x2s are coming…but when?: We’ve been hearing a lot over the past year about the advantages of 6×2 axle configurations, where power is supplied to only one drive axle, providing about 400 lbs of weight savings or fuel economy improvements of 2-3%. But in Canada, several provinces still do not allow the technology. I sat down with Joe ElBehairy, v.p., engineering and quality with Meritor for an exclusive interview and he told me Meritor and other companies have been actively lobbying all the provinces to allow 6x2s. Ontario and Quebec, it turns out, have dug in their heels and provided the most resistance. The concern they have, it seems, is that in situations where the non-driven axle is liftable, that drivers could lift that axle while under load and potentially cause road damage. This is new news, by the way, from within the past couple weeks.
“We have been working with a mini-consortium to try to address some of the challenges in Canada and the two that are really resisting are Quebec and Ontario,” Joe told me. “Specifically, it’s the load-shifting technology that’s necessary to enable the traction. They don’t allow it because their concern is, there’s nothing to control it from being done full-time and not just in a traction event…If you expand to, in an extreme situation where you can lift the axle and turn it into a 4×2, somebody would do that for fuel economy reasons. We are currently discussing this with Ontario and Quebec and that is really the limitation we have right now. The other provinces have agreed with us and are okay in accepting it; it’s those two that have stepped back.” Look for my complete interview with Joe on Trucknews.com later.
The dangers of downspeeding: The other trend we’ve been hearing a lot about is engine downspeeding – running at lower rpms with faster rear axle ratios to improve fuel economy. The idea is that for every 100 rpm slower the engine runs at 65 mph, fuel savings of 1.5% can be achieved. However, engine downspeeding also increases torque loads on the axles and driveshaft, meaning truck buyers should spec’ axles and driveshafts designed to handle the extra torque.
Speaking at a press conference at Mid-America, Steve Slesinksi, director product planning at Dana, noted that moving from a 3.55 to a 2.26 rear axle ratio increases the torque load on the driveshaft and axle by 57%. Even going from a 2.64 to a 2.26 ratio increases torque by 14%.
Meritor’s Joe ElBehairy told me in our interview, fleets need to be mindful of this when spec’ing new vehicles. “In order to have acceptable level of startability, the engine torque and drivetrain torque increases,” he said. “It’s really critical to make sure that as (rear axle ratios) get faster, you’re not overloading the rest of the system. And beyond that, they need to make sure the transmission, driveshaft and axles are all linked up in terms of those torques that go through the system. Customers have to look at things a little bit differently. They have to understand the technologies and how things interact more than they used to. There’s just a lot more interaction between the engine, transmission and the axle than there used to be.”
The shift towards automation: It’s no secret that more fleets are buying trucks with automated transmissions, but for the first time at MATS I saw some hard numbers that attest to this trend. Eaton announced during its press conference that presently, 20% of the North American Class 8 truck build features automated transmissions. The company expects that to expand to 30% within three to five years.
Eaton has expanded availability of its newest-generation automated transmission, an optimized version of which can now be mated to the Paccar MX engine. It also made its SmartAdvantage powertrain package (an Eaton AMT coupled with a Cummins ISX12 or ISX15 engine) available in Volvo trucks. Also on the topic of automated transmissions, Daimler’s DT12 has now sold 17,000 units since its launch just last year. The shift towards automation is one trend I don’t think you’ll see reversing any time soon.
The case for bigger engines: The past few years have seen a significant shift towards smaller displacement 13L engines and the reasons seem obvious. More power is being packed into 13L engines (Mack’s David McKenna once said the company can coax 39 hp of power per litre out of today’s engines, compared to 20-25 hp in the past), and because they weigh less it stands to reason fuel economy will be improved. Not always the case, Cummins countered during recent press conferences at MATS and TMC.
Cummins insists its ISX15 is the industry’s most fuel-efficient engine. But how is that possible? It seems counterintuitive that a 15L would sip less fuel than a 12- or 13L. “There’s a tangible advantage to 15L big bore power,” said Jeff Jones, v.p. of Cummins North American engine biz. He said it’s because: the additional power gives engineers more flexibility when it comes to optimizing performance at low rpms; big bore engines offer higher compression ratios; and because the turbocharging mechanism is simpler in higher displacement engines. These engines are now able to cruise at 1,100-1,300 rpm – unprecedented with 15L power. Maybe the industry-wide migration to 13L power has been overstated. Keep in mind, Navistar, which despite its troubles still holds a significant share of the market, stopped offering 15L power for a spell there, giving its customers no choice but to make the switch. It will be interesting to see whether there’s a reversal – or levelling off – of this perceived shift towards smaller displacement engines.
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