Light Duty Vehicle Fuel Economy Improvement from Increased EGR, 03-R9614

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Principal Investigators
Shin-hyuk Michael Joo
Terrence A. Alger
Charles E. Roberts

Inclusive Dates:  04/01/06 – 10/01/07

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 in the past 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 research efforts and in the High Efficiency Diluted Gasoline Engine (HEDGE®) consortium, increased EGR levels combined with improved ignition systems have shown the potential to substantially decrease fuel consumption. However, the technology identified as part of the HEDGE concept (very high EGR [approximately 50 percent], ultra-high energy ignition, boosted, high-compression ratio operation) is several years away from implementation in a production engine. The project's approach to this problem is very simple. This research 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. These experiments will be performed 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 -

  • Successfully modified a stock vehicle to apply moderate EGR operation technology and demonstrated the capability to take over vehicle control using an in-house controller
  • Demonstrated that a moderate amount of EGR can replace "severe fuel enrichment" plus "severe retardation of ignition timing" strategy to keep exhaust temperature low for C/C and to prevent engine knocking
  • Improved engine out CO emissions dramatically using moderate amount of EGR at WOT without significantly deteriorating UHC and NOx.
  • Improved combustion phasing at WOT by mitigating engine knock using EGR.
  • Driveability of the test vehicle at the present is excellent, such that it will perform well as a demonstration vehicle for SwRI's EGR engine technology.
  • Achieved good fuel economy and better than baseline vehicle HC and CO emissions although NOx emissions were higher than baseline because of low catalytic converter efficiency caused by air-to-fuel excursion.

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