Overview: In the past decade the development of advanced electronically controlled heavy duty diesel engines has led to significant improvements in performance, fuel economy and longevity. The flexibility and sophistication of these engine control programs has made it possible to significantly alter the engine calibration based on a range of operating conditions. The ability to dynamically switch between a certification mode to an off FTP mode forms the basis of the recent EPA consent decree settlement. In response to this agreement, engine manufacturers have agreed to develop low NOx Rebuild Kits including electronic calibration programs. These recalibration programs can effectively reduce the emission rate and limit the impact of the off cycle operation. The advances in diesel technology are not limited to electronic controls alone. The use of advanced materials and manufacturing has further extended the useful service life well beyond a million miles for many applications. In the absence of exhaust after treatment, the deterioration factor for engine out emissions remains low when compared to light duty gasoline powered vehicles. The combined impact of these technological improvements on the mobile source emission inventory is not well understood. In effort to characterize the deterioration factor of HDDs and explore the effectiveness of restorative maintenance including Low NOx engine control programs, the California Air Resources Board established Measure 17 (M17). The purpose of M17 is to evaluate the viability of chassis dynamometer HDD I/M program to supplement existing I/M efforts. The program goal is to reduce NOx emissions by 10 tons per day and ROG emissions by 1 ton per day within the Southern California Air Basin by The results from the initial phase of testing of 100+ HDD trucks suggest the NOx emission rates are higher than the certification values and the dispersion of the population has increased in recent years, Figure 1. The initial information suggests the reduction potential for mechanical repairs alone is approximately 4% at a repair threshold of 10 gram/wheel horsepower-hour. Progressively lower reductions are achieved when the repair threshold is decreased. In some instances the mechanical repairs have resulted in an increase of NOx emissions, Figure 2. A subset of these test vehicles were subjected to both mechanical repair and Low NOx reprogramming. The results indicate that a 24% reduction in NOx emissions on average can be achieved with only modest reduction in fuel economy for most trucks. The average cost of the repair and reprogramming is $753 per truck with a cost benefit of $0.68/ lb of NOx reduced. CARB Stockton HDD Test Facilities: Superflow Model 602 tandem roll 36” hydrokinetic dynamometer California Analytical Instruments emissions bench measuring raw exhaust Total flow is determined using a Superflow Air Turbine attached to the intake. Evaluation of the Effectiveness of Low NOx ECM Reprogramming to In Service Heavy-Duty Vehicles Matthew R. Smith, Ted Younglove and Wayne Miller – UC Riverside CE-CERT Donald Chernich, Robert Ianni, Tullie Flower, Mark Burnitzki, Mike Bernard and Roelof Riemersma – CARB Program Sponsor: California Air Resources Board Figure 3. Typical Stockton HDD Lab Power Curve Figure 1. M17 NOx Emission Rates for HDD Trucks Tested at Stockton Lab Figure 2. M17 NOx Reductions for Mechanical Repair Only Test Cycle Development: Candidate cycles must provide sufficient dynamic load to accurately characterize the vehicle emission behavior. Cycle length should be minimized to reduce overall vehicle downtime and maximize vehicle throughput. Test must be repeatable for a broad range of vehicles. Replicate testing is required to provide a solid foundation for inventory and enforcement purposes. Combine two separate cycles, a power curve and a series steady state sampling modes. Test Methodology: Power curve Test - Vehicle is tested in direct drive, engine operating at the governed maximum rpm. Load is gradually applied while the engine RPM remains essentially constant until the peak power is reached. Lug down occurs as engine RPM drops and torque rises to Lug point usually between 1100 and 1400 rpm. The load is then removed at the conclusion of each test. Repeat sequence three replicate tests are obtained. Steady States Test - Steady state test replicate freeway driving under three load conditions, 25, 50 and 75% of peak power. The vehicle is operated at 60 mph in direct gear for a period of 3-5 minutes at each load point. Duration is sufficient in many cases to capture engine switching to an off FTP control strategy. Figure 4. Off FTP Switching During Steady State Operations Nox (g/whp-hr) Data Reduction and Analysis: Compare incremental ramp and lug down segments on a range of low, medium and high horsepower trucks. Combine those regions with the lowest test to test variability. Analysis region is between 100 hp and extends to the power peak. Analysis of mass emission rates in terms of g/mile, g/gallon and g/whp-hr. Least variability found in g/whp-hr. Primary standard in terms of “brake” horsepower hour however wheel horsepower is measured directly. Dynamometer is a power absorber only – no way to determine the drive train losses by motoring. Processing the Data Test data analyzed using a binned integrated modal approach in terms of g/wheel horsepower hour. Values are higher than the certification, due to transmission and driveline losses – 15%-25%. Replicate sequence of 3-4 power curve tests are collected for each vehicle. Individual and triplicate tests are validated using a comprehensive quality assurance algorithm. QA for CO, CO2, THC, NOx and fuel economy. Acceptance criteria requires the integrated coefficient of variation, (COV =stdev/Average) <5% Figure 5. Replicate Power Curve Test RepeatabilityFigure 6. Binned Power Curve Test Data Test, Repair and Reprogram Results: 5 candidate vehicles were tested, (4) power curve and (1) steady state test. All vehicles were subjected to basic tune up, injector flush, check injection timing set factory settings and minor equipment repair, cost $200-$1031/truck, average $752/truck. All vehicles were reprogrammed using OEM updated Low NOx calibration. Trucks were retested using a similar sequence to baseline. Emission reduction for NOx ranges from 5% - 40%, average 24% reduction. Comparable mechanical repairs alone result in a 4% reduction at 10 g/whp-hr and $935/truck. Cost effective alternative to more expensive repairs at $1,354/ton of NOx. Comparable mechanical repairs alone result in a $6,940/ton of NOx. Conclusion: The improvements in diesel technology have increased the useful service life of HDD trucks beyond 1M miles in many applications. These advancements in durability and electronic engine calibration will have a significant impact on the emission inventory for many years. The costs of alternative emission reduction strategies, scrappage, after treatment, engine repower and mechanical repair are significant. Updating engine control programming represents a quick and cost effective alternative emission reduction strategy which can be applied to current and future generations of HDD trucks. Figure 7. Reprogramming Test Matrix and Results Figure 8. Pre and Post Steady State NOx Emissions Seconds