The Basics of Downspeeding
Efficiency is crucial when it comes to managing fleets of trucks. Fuel is often one of the most significant expenses that comes with maintaining a fleet, so it’s only natural that any opportunity to reduce those costs would be of great interest. On top of that, there’s the added pressure to reduce the environmental impact caused by trucking. Engine downspeeding is a concept that covers both of those issues.
What is Downspeeding?
The higher an engine’s RPMs, the more fuel it uses. Engine downspeeding works by reducing an engine’s RPMs while traveling at cruise so that the engine is able to use fuel more efficiently. Simply reducing an engine’s RPMs is one thing, making sure the engine still has adequate torque is another. Ideally, downspeeding should hit the right balance between fewer RPMs and maintaining enough power.
Downspeeding improves fuel efficiency by reducing the number of times a piston moves up and down, reducing heat and friction. The reduction in heat further benefits by improving thermodynamic efficiency and reducing wear and tear on components.
Downspeeding & Efficiency
The main concept of downspeeding is hardly new, but it’s become an increasingly important concept over the past decade as technology evolved to make it easier for drivetrain performance to automatically adjust to road conditions.
For companies that operate fleets, fuel represents one of their most significant expenses and any amount of fuel savings can really add up. As the above graphic demonstrates, improving fuel efficiency by just 1% can make a big difference in the amount of fuel a truck uses. And that’s just for one vehicle. In some cases, fuel efficiency could be even greater. Overdrive highlights Volvo’s XE13 package from 2011 as an example, which reduced RPMs at cruise from 1,370 to 1,150, resulting in fuel savings of more than 3%.
The Challenges of Downspeeding
As beneficial as downspeeding can be, it does have its downsides. When planning for downspeeding, it’s important to think about the larger impact it will have on the drivetrain. When downspeeding was really beginning to become an issue, many were surprised to find out that the faster gear ratios needed for downspeeding could potentially place an excessive amount of torque on the drivetrain and cause components to wear out faster, making it extremely important for all components to be carefully spec’ed.
It’s also worth noting that downspeeding isn’t necessarily an ideal solution in every case. To get the most out of it, it’s best for trucks that spend a significant part of time in the top two gears.
