Light-Duty Vehicle Fuel Economy
Improvement from
Increased Exhaust Gas Recirculation, 03-R9614
Principal Investigators
Shin-hyuk Michael Joo
Terrence A. Alger
Charles E. Roberts
Inclusive Dates: 04/01/06 – Current
Background - The objective of this project is to investigate the potential of moderate levels of exhaust gas recirculation (EGR) to improve fuel economy in a light-duty automotive application. In light-duty vehicles, EGR has been used to reduce engine-out NOx emissions and reduce pumping losses, but has recently fallen out of favor with vehicle manufacturers for several reasons. The primary reason is that EGR levels need to be tightly controlled in a transient situation to prevent misfires and engine instabilities, and current engine computers are not programmed to accomplish this control. Secondary considerations are cost and the ability of three-way catalysts to meet NOx targets without EGR. In addition, the level of EGR required to make significant fuel economy improvement is higher than most manufacturers are accustomed to running. Given these constraints and SwRI’s recent successful experience with high EGR engines, this project’s work scope includes modifications of a production vehicle’s hardware to run moderate (less than 20 percent) EGR levels during transient drive cycles and re-tuning the engine computer to maintain tighter control over the EGR level.
Approach - Based on data taken during previous internal research programs (for example, 03-9386, 03-9525) and in the High-Efficiency Diluted Gasoline Engine (HEDGE®) consortium, increased EGR levels combined with improved ignition systems has shown the potential to substantially decrease fuel consumption. However, the technology identified as part of the HEDGE concept (very high EGR (~50%), ultra-high energy ignition, boosted, high compression ratio operation) is several years away from implementation in a production engine. Our approach to this problem is very simple. We will demonstrate benefits of a moderate level of EGR (approximately 20 percent) combined with an improved, but still production-ready, ignition system that is immediately available to the OEMs (original equipment manufacturer). The success of this project will also prove that the high EGR concept is viable in a production unit. We will perform these experiments on a vehicle rather than on an engine. By doing so, SwRI will be able to produce real FTP-75 (Federal Test Procedure) data for those interested in the benefits of this kind of engine operation.
Accomplishments - SwRI has received a grant test vehicle from an international vehicle manufacturer. Upon receipt of the test vehicle, SwRI instrumented it for use on the chassis dynomometer. A detailed instrumentation package was installed on the vehicle to monitor all important parameters during operation. A cylinder pressure transducer was mounted as well to acquire cylinder-by-cylinder data and burn rate information. The vehicle has been run through the FTP-75 and Highway cycle three times each. Emissions have been measured at both pre- and post-catalyst locations for raw emissions. Diluted bag emissions have also been measured. Fuel economy results on “City” and “Highway” cycles are 26.03 mpg (average of three tests) and 36.29 mpg, respectively.
