SCR or EGR is the question that is facing organizations in both the transportation and service sectors. Historians say that history repeats itself and it did just that last month when equipment orders doubled the previous month mirroring the purchases October and November of 2007 just prior to the last significant change in emission regulations. Sources in the industry believe this spike is caused not by freight or service demands but in effort to capture the last remaining build slots prior to the new wave of technology and the imminent price increases. The current situation is also reflective of 2007 on the technology side when manufactures were scrambling to develop, test and tout their respective technologies. At the time, in theory, Caterpillar had the most notable system, which would actually overcome some of the additional fuel used during the regeneration* process. However they were unable to make that system function consistently in practice, which precipitated their exit from the highway use, heavy-duty engine market. Currently, the remaining players in the industry are at odds, in the courts, with the EPA, and the media. One is gambling on what they call the in-cylinder solution (EGR) whereas the other players are going with the SCR (Selective Catalytic Reduction) solution, which incorporates the use of a DEF (diesel exhaust fluid) to meet the 2010 regulations. Another correlation to the situation is that one group is predicting an increase in fuel economy while the other is gambling on unconfirmed technology. The following is a brief overview of the two (2) opposing approaches to the technological challenge of reducing oxides of nitrogen (NOx) to meet the 2010 requirement.
SCR (Selective Catalytic Reduction), in short, will inject DEF (Diesel Exhaust Fluid) into the exhaust stream at a precise time to reduce NOx gases. The manufacturers predict this process will reduce the number of regenerations* and improve fuel economy to the point it will overcome the cost of the DEF fluid and provide an additional three (3) percent improved fuel economy. All major manufacturers except International plan to introduce this system. The pros & cons are as follows:
- Technology has functioned with minimal problems in Europe for several years.
- Improved fuel economy (predicted).
- Reduction in particulate matter (predicted).
- Reduced DPF (Diesel Particulate Filter) maintenance (predicted).
- Initial cost of SCR system compared to 2007 DPF technology.
- Additional system to maintain.
- Cost to maintain the system.
- Driver and mechanic training on the system.
- Freezing concerns of the DEF fluid and heater reliability.
- Environmental impact of the DEF fluid.
- Drivers' commitment to keeping the DEF fluid replenished.
- Availability of DEF fluid in remote locations.
- Properly configured fueling locations so both tanks can be replenished simultaneously.
- Availability of replacement parts.
*Regenerations occur when the DPF (diesel particulate filter) pressure sensors sense the filter (muffler) is becoming plugged with diesel ash from the diesel combustion process. At this point the system will inject diesel fuel into the filter to remove the ash. All systems since 2007 have incorporated this process however it is detrimental to overall fuel economy.
EGR (Exhaust Gas Recirculation) re-routes exhaust gases back into the combustion chamber to reduce the oxides of nitrogen NOx. This coupled with increased injection pressures, modifying the EGR flow rate, redesigning the piston bowl, and advanced turbo-charging, is how International plans to approach the new requirement. The pros & cons are as follows:
- No additional fluid to replenish
- No additional driver interaction
- No appreciable weight increase to the chassis
- Initial cost of the MaxxForce engine & subsequent technologies.
- Engine maintenance cost due to functional changes.
- EPA Certification (must use credits to meet regulation).
- Unproven technology.
- No gain in MPG/additional loss of MPG.
- EGR & Turbo charger reliability.
- Added technology to an already complex system in an industry starving for competent technicians.
- Breakdown or out-of-service frequency.
- Part availability due to new International (MaxxForce) engine technology.
- Overall engine life.
As evident from the respective lists, some of the concerns are consistent while others are unique to each of the new technologies. Both parties in question have answers to all these "prefect world problems/challenges" but you've probably figured out by now, we don't live in a perfect world. In short, SCR solves the problem by adding an additional step/system and fluid to the process but it does in fact meet the new regulation; whereas, International adds additional technology to the existing system and does not improve or claim to improve the MPG. Given the aforementioned factors, it's a slippery-slope for consumers of these new units and it is understandable why the remaining build-slots were utilized.
The only guarantees at this point are: the cost is going to increase and the legal battles will continue, with neither system approved beyond 2011. The end result will undoubtedly be cleaner air to breathe for current and future generations, but there's an outside chance the industry could lose yet another supplier if their respective technologies don't function as designed.