From strictly workhorses to luxurious personal vehicles, many drivers choose diesel. Diesel engines have changed significantly over the years, and with changes to the engine come changes to maintenance and application. Technical director, Roger Dale England, PhD, and Michael Wedding, engineering and technical manager at Valvoline, share their insight to the changing world of diesel engines and other changes in the industry.
MWS: HOW HAS THE WORK TRUCK MARKET CHANGED SINCE THE ADDITION OF A TRUE MEDIUM-DUTY DIESEL ENGINE BY DODGE IN THE 1980S?
I believe that Dodge’s innovation of installing the Cummins 5.9-L into a pickup truck was the spark that ignited this entire market segment, creating the diesel culture we see today. Prior to Dodge’s introduction of the 5.9-L Cummins diesel, the market was dominated by gasoline engines, which limited the scope of use of these vehicles. The rise of the medium-duty diesel led to an increase in the size and weight of all types of trailers, both recreational and commercial. For example, prior to this engine option, enclosed race car trailers were very uncommon. Now, we see diesel pickup trucks pulling stacker trailers.
Also, drivability and comfort increases in Class 4 trucks over the past 30 years allowed people to use these as daily drivers, something I personally have done for the past 20 years. Today’s Class 4-6 trucks are luxurious, with great acceleration, handling, and a very smooth ride—further adding to the volume of this market segment. If you have never driven a circa 1970 1-ton truck, do yourself a favor and try it. You will have a much greater respect for the engineering expertise of today’s truck designers and manufacturers.
The other option that people had in the 1980s was a “small” diesel Class 6 truck to use for their excavation or landscape businesses. Recall that at the time, the power numbers for gasoline engines were far from impressive. As soon as you surpassed the functionality of a gasoline “big block” engine for moving equipment or other loads, the option was to step up to a large dedicated “semi” truck.
I think, for England, “diesel” and “turbo diesel” are synonymous because the prior naturally aspirated diesel engines are hardly worth mentioning. What is missed by some people is that the 5.9-L Cummins was the first TURBO diesel option in a pickup truck. The usable torque and power of a large tractor engine in a small pickup was clearly a market disruption.
MWS: WHAT RECENT CHANGES HAVE WE SEEN IN THE VOCATIONAL MARKET?
The power densities available in the vocational market are impressive. There are small cab-over trucks with 4- to 6-cylinder diesel engines that generate sufficient power in a small under-cab configuration to make deliveries and to move product from distribution centers to stores and customers as needed. The cab-and-chassis offerings from the big three, which can be fitted with numerous utility/vocational “beds,” are now offering up to 900 lb-ft of torque in what looks similar to a pickup truck.
Natural gas is finding more and more use in the vocational market. Huge swings in the cost of diesel fuel and government incentives helped get natural gas engines out of the little niches and into the mainstream. In vocational applications such as ready-mix, local delivery, and transit busses, CNG logistics work well with nightly re-fueling. As the years progress, we see more and more long-haul Class 8 applications, but the vocational market is still big in CNG.
MWS: WHAT ARE THE MAJOR CHANGES IN THE DUTY CYCLE FOR A TYPICAL CLASS 4 TRUCK OVER THE PAST 10 YEARS?
While I am unaware of exact specifics, it seems that we are continuing toward better utilization of equipment and more dedicated use. In construction equipment, we don’t see as many multi-use equipment (think backhoe) as we do purpose built pieces (wheeled loader, tracked excavator, and articulating trucks). In the Class 4 market, we seem to be moving away from general “pickup” trucks that can do a bit of everything; better utilization of equipment allows dedicated trucks for delivery (box and flat beds), rollbacks, and such.
MWS: HOW DOES THE CONSISTENT YEAR-OVER-YEAR INCREASES IN CLASS 2 TO 5 TRUCK POWER DENSITY AND LOAD CAPACITY AFFECT THE LUBRICATION REQUIREMENTS OF THE ENGINE?
Today’s diesel engines put more stress on engine oil than ever before. Now, medium-duty diesel engines have higher cylinder pressure, higher crankshaft main and journal bearing loads, and hotter pistons—which lead to an increase in power density and efficiency, as well as decreased emissions. Oil today is expected to inhibit corrosion, seal piston rings, clean engine components, cool the pistons, and not interfere with the chemical reactions in the aftertreatment. All this in addition to lubricating. With this wide array of functions comes a variety of opportunity for advancements when the oil is engineered in parallel to the engine. At Valvoline, we have a seat at the table when Cummins is developing the next generation of its engines, and that allows us to continue to create more value and increase efficiency and durability. I’m particularly impressed that the large increases in power density have not decreased longevity, and lubrication advancements have played a key role in that achievement.
MWS: HOW DOES THE MIGRATION TO AUTOMATIC TRANSMISSIONS AFFECT TRANSMISSION FLUID FORMULATION AS POWER AND WEIGHT ARE INCREASED?
The growth in use of automatic transmissions are making for an easier point of entry for young drivers who may have never operated a manual transmission. At the same time, automatics reduce the physical demands on experienced drivers who may be exhausted from either city driving or the manual work they are doing at each stop of their vocational vehicle.
The need to run the engine at its most efficient speed and load has increased the number of gear ratios needed for today’s medium-duty vehicles. Adding more gears under the same general space envelope decreases gear sizes, leading to decreased gear contact areas and—along with increased engine torque capability—has driven gear loading to very high levels. At the same time, the fight for increased efficiency required the deployment of lower viscosity fluids. This pushed automatic transmission fluid technology forward at a rapid rate. The fluid we are manufacturing today is not like anything ever available in the past—it has capabilities well beyond what was considered possible only a few years ago. Engineering a lubricant with a strong traction coefficient sounds bizarre, as it probably should. We are creating a fluid that acts like a lubricant between gears, while allowing the friction necessary for the clutches to function under high loads. These advancements make this an exciting time to be associated with this technology.
With increased power densities, the medium-duty transmissions have to handle all of that power and torque while also constrained within package sizes. All of the demands that England addresses are handled with smaller sump sizes increasing the need for oxidation control.
MWS: HOW HAS THE TECHNOLOGY IN COOLANT CHANGED AS ENGINE MANUFACTURERS INCREASE CYLINDER TEMPERATURES, ADD COOLED EGR AND MORE COMPLEX HEAT MANAGEMENT SYSTEMS TO THEIR ENGINES, ETC?
EGR cooling to reduce NOx is a huge demand on the cooling system. I have been told that 70 percent of the cooling system capacity on a Class 8 truck is used by the EGR cooler. If not directly proportional to medium-duty engines, it must be comparable. The use of different metal alloys cannot be ignored. Aluminum heads affect the use of OAT, HOAT, NOAT, and Nitrite-free coolant technology.
Since heat is energy and energy is power, this temperature management is key to efficiency, power density, and many of the topics we discussed. Too often we see customers buying cheap recycled coolants that are of very low quality. This may be costing them money at the fuel station in addition to robbing them of equipment life and reliability.
MWS: ELECTRIC PROPULSION IS A POPULAR TOPIC IN THE MEDIA. HOW WILL ELECTRIFICATION AFFECT THIS MARKET SEGMENT?
I spoke earlier about Natural gas vehicles, and I believe that electric vehicles are following some of the same entry points into the commercial vehicle market.
Electrification is growing fastest where legislation is strong. For plug-in, 100 percent electric vehicles, it seems that battery size/weight and related range constrains their adaptation, and emergency vehicles will likely not rely on electricity sources that could be disrupted by natural disasters. Much like the early adoption of CNG vehicles, some vocational applications with limited range demands and daily return-to-home applications are starting to experiment with plug-in, 100 percent electric vehicles.
Hybridization, as seen in passenger cars, is likely to grow in popularity. Internal combustion is often more efficient than electric and, overall, hybridization can add efficiency without range concerns—an obvious attraction. Hybrid systems may be added on to a truck build just like any other component that a customer would select. Emerging options include axle applications, systems connected through a transmission PTO, or integration to the transmission torque convertor. The electric power can assist in controlling cabin temperature when the truck is not running, powering hydraulics or allowing for smaller engines, and on-demand power for hills and stop-and-go traffic.
If not overly influenced by legislation, there will likely be several forms of energy that find their fit into the market.