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Reduction of Octane Requirement by Knock Sensor Spark Retard System
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English
Abstract
A 1975 California model automobile with an 8:1 C.R. 350 CID engine was modified by increasing the compression ratio to 9:1 which resulted in improved fuel economy. The higher NOx emissions were reduced to the base level by substituting a back pressure-controlled EGR unit for the original valve and increasing the EGR flow. Octane requirement was controlled by a knock sensor-actuated spark timing retard system. The knock sensor (accelerometer) is attached to one of the cylinder heads of the engine. When knock occurs, the vibration is picked up by the sensor, the signal is filtered to remove some of the engine background noise, and the knock pulse is detected. When the amplitude of the detected knock signal exceeds a threshold, the spark timing is retarded. When no knocking is detected over a waiting period, the timing is advanced back to its normal schedule. Using this system, the vehicle's octane requirement can be lowered several numbers with some performance debit, i.e., slower acceleration times.
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Citation
Kraus, B., Godici, P., and King, W., "Reduction of Octane Requirement by Knock Sensor Spark Retard System," SAE Technical Paper 780155, 1978, https://doi.org/10.4271/780155.Also In
References
- Wostl W. J. Heintz J. A. “Knock and Rumble Detector for Internal Combustion Engines.” November 17 1970
- Krause W. H. “Knock Detection Instrument.” August 24 1965
- Barton R. K. Lestz S. S. Duke L. C. “Knock Intensity as a Function of Engine Rate of Pressure Change.” Paper 700061 SAE Meeting Detroit January 12-16 1970
- Keller B. D. Wright L. T. Ginsburgh I. Rueckel H. E. “Automated Fuel Road Octane Ratings.” Paper 730550 SAE Meeting 1973
- Arrigoni V. Gaetani B. Ghezzi P. “Method and Apparatus for Measuring Knocking in Internal Combustion Engines.” March 9 1976
- Harned J. L. “Borderline Spark Knock Detector.” March 22 1977
- Corner E. S. Cunningham A. R. “Value of High Octane Number Unleaded Gasoline in the U.S.” A.C.S. Los Angeles March 1971
- Gumbleton J. J. Niepoth G. W. Currie J. H. “Effect of Energy and Emissions Constraints on Compression Ratio,” Paper 760826 SAE Meeting Dearborn, Michigan October 18-22 1976