When the EPA got diesel engine exhaust emissions about as low as it could, the agency set out to find new ways to reduce air pollution and slow the effects of climate change. This happened in three stages, starting with lowering allowable nitrogen oxides (NOx) in October 2002 in advance of 2004 regulations. In 2007, the EPA mandated diesel particulate filters (DPF) to limit particulate matter (PM) such as soot, ash, and unburned hydrocarbons. In 2010, NOx and PM limits were reduced to levels impossible to measure only a decade earlier. We now have the cleanest burning on-highway diesel engines in the world.
Until now, only PM and NOx were considered, but carbon dioxide (CO2) was omitted from the calculations. The newest emission requirements, or GHG 2014, involve CO2 and fuel efficiency.
Reducing CO2 emissions
The new metrics will be based on work done, not just power produced. CO2 emissions will be measured in grams per ton mile. Fuel economy will also be measured per ton mile. The goal is to reduce CO2 and diesel consumed by 20% from 2014-17. More reductions will take effect for model years 2018 and beyond.
Vehicle and engine builders have had typical on-highway and vocational truck configurations benchmarked to account for varying marketplace needs. It would be improper and inaccurate to use one set of ton-mile figures for on-highway and all the variations and sizes of vocational trucks.
Even using the National Highway Traffic Safety Administration’s established weight classes would fail to account for application differences in Class 8 (33,000 pounds and greater gross vehicle weight rating/gross trailer weight rating) trucks alone. Freight trailers and dump trailers differ widely, as do tanks and equipment haulers. Not only are they configured differently with different aerodynamics and other characteristics; their operating profiles vary widely.
Measurements will vary
With EPA 2004, 2007, and 2010 regulations, emissions could be measured at the tailpipe. There were absolute limits. But GHG 2014 regulations allow for vocational variations. It would be unfair to measure a tractor pulling a van trailer with the same yardstick as a ready-mix truck. That is why truck builders and engine makers average their results.
EPA states, “Not every truck has to be compliant, but every truck has to be certified. It’s up to the OEM to ensure they have enough adoption of those [advanced] technologies across the fleet.” Technologies available to users run from low rolling resistance and wide base single tires to natural gas or hybrid power.
The OEM must demonstrate the value of various technologies to the buyer. Then the OEM can average the mileage improvements and CO2 reduction over the entire range of trucks sold. Not all trucks sold as certified may meet GHG 2014 reduction targets, but they will be averaged with those that do.
Technologies will be grouped according to application, as engine- or vehicle-related. For example, biofuels, alternative fuels, and fuel management technologies will be measured according to use-specific test cycles. Those results will determine an engine’s certification of meeting its CO2 standard.
Using results of coast-down and other forms of testing, EPA assigned baseline values to trucks and efficiency values for devices to be added or removed from trucks. These could include weight reduction, fuel-efficient tires, idle timers, and vehicle speed limiters.
It will be up to vehicle operators to maintain each vehicle in its as-purchased condition. On-board diagnostics assure against malfunctions in vehicle operations compared to its original condition.
Any malfunction or variance in any of 38 systems being monitored will be recorded in the engine computer. It could violate federal regulations if not addressed in a timely manner. Transient malfunctions such as temporary stoppage of diesel exhaust fluid flow at start-up if the fluid is frozen will be recorded and stored, even if the malfunction indicator light goes out when the fluid thaws. When the malfunction indicator or check-engine light stays on, the truck should be taken to the shop.