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Comparison of Computer Predictions and Experimental Tests for Two-Stroke Engine Exhaust Systems
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English
Abstract
The effect of exhaust system configuration upon performance of two-stroke engines is explored. Computer predictions of gas dynamic behavior in the exhaust pipes are compared to experimental results of real pipe tests. Predicted pressure, velocity and temperature histories at key points in the exhaust system explain the relative power differences for the test pipes. Predicted volumetric flow rates show the effectiveness of exhausting gases at larger pipe cross sectional areas in reducing noise output.
The application of the computer predictions to a Yamaha RS 100 offers an explanation for the experimentally measured loss of power at mid-range engine speeds encountered using one of the two test pipes. A relative comparison of the two systems shows that the differing pipe geometries cause predicted pressure and velocity histories to change. These changes are correlated to actual power curves.
An experimental exhaust system is presented for the Yamaha 360 MX which increases power and is quieter than the stock system. Computer predictions are used to explain the increased performance.
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Authors
Citation
Ospring, M., Karnopp, D., and Margolis, D., "Comparison of Computer Predictions and Experimental Tests for Two-Stroke Engine Exhaust Systems," SAE Technical Paper 760172, 1976, https://doi.org/10.4271/760172.Also In
References
- Dwyer H. A. Allen R. Ward M. Karnopp D. C. Margolis D. “Shock Capturing Finite Difference Methods for Unsteady Gas Transfer” AIAA Paper 74-521 Palo Alto, California 1974
- Ward M. “Gas Dynamic Simulation of a Two-Stroke Engine” University of California at Davis, Mechanical Engineering Department February 1975
- Kelsay R. E. “Experimental Investigation of Two-Stroke Engine Performance” University of California at Davis, Mechanical Engineering Department February 1975
- “Motor Vehicle Noise Laws and Regulations” California Motor Vehicle Code 1972
- Jennings G. “Do you Really Want to Know About Expansion Chambers?” Cycle Magazine April May 1972
- Rogowski A. O. “Elements of Internal Combustion Engines” McGraw-Hill Book Company New York 1953
- Naitoh H. Taguchi M. “Some Development Aspects of Two-Stroke Cycle Motorcycle Engines” Paper 660394 SAE
- Huelsse W. A. “Investigation and Tuning of the Exhaust System of Small Two-Stroke Cycle Engines” Paper 680469 SAE
- Kinsler L. E. Frey A. R. “Fundamentals of Acoustics” Wiley and Sons New York 1962
- Ospring M. J. “Comparison of Computer Predictions and Experimental Tests for Two-Stroke Engine Exhaust Systems” University of California at Davis, Mechanical Engineering Department June 1975
- Murphy M. J. “Large Amplitude Wave Propagation in Variable Area Ducts” University of California at Davis, Mechanical Engineering Department June 1975