EXHAUST TUNING ON A FOUR-STROKE ENGINE; EXPERIMENTATION AND SIMULATION
Date Published: 2001-12-01
Paper Number:2001-01-1797
Author(s):
Gordon P. Blair - Queen's University of Belfast
D. O. Mackey - OPTIMUM Power Technology
M. C. Ashe - OPTIMUM Power Technology
G. F. Chatfield - OPTIMUM Power Technology
A Yamaha YZ400, 5-valve, 4-stroke cycle, motocross racing, motorcycle engine is instrumented to provide pressure diagrams in the exhaust system which are recorded over the usable engine speed range at full throttle from 5000 rpm to 11000 rpm. The engine produces a maximum of some 34 kW (46 hp) power output. The production muffler-ended exhaust system is replaced with two alternative and more highly-tuned exhaust systems, namely a straight pipe and a straight pipe and diffuser. The complete engine geometry together with these two exhaust systems is simulated using an engine simulation software package (VIRTUAL 4-STROKE) and the experimentally-recorded exhaust pressure diagrams and performance characteristics of power, torque, etc., are compared with the predictions of the theoretical simulation.
The variation of exhaust system produces differing performance characteristics whose origins the measured pressure diagrams and recorded performance characteristics struggle to explain. The simulation, on the other hand, not only computes accurately the exhaust pressure diagrams and the performance characteristics over the entire speed range but also explains the origins of the variations in these performance characteristics. This illustrates not only the effectiveness, or otherwise, of this type of exhaust tuning on four-stroke engines but also the effectiveness of an accurate engine simulation as a design and development tool. Finally, from the experimental and simulation evidence presented the paper draws numerical conclusions on empirical design factors for the basics of exhaust system tuning.
Blair G.P., Design and Simulation of Four-Stroke Engines, Society of Automotive Engineers, R-186, ISBN 0-7680
0440-3, August 1999, p.815.
Blair G.P., Design and Simulation of Two-Stroke Engines, Society of Automotive Engineers, R-161, ISBN 1-56091-685-0, February 1996, p.623.
Winterbone D.E., Pearson R.J., Design Techniques for Engine Manifolds, Professional Engineering Publications, 1999, p.364.
Winterbone D.E., Pearson R.J., Theory of Engine Manifold Design, Professional Engineering Publications, 2000, p.476.
OPTIMUM Power Technology, Bridgeville, PA, VIRTUAL 4-STROKE engine simulation software, viz. Internet at optimum-power.com.
Blair G.P., Mackey D.O., Ashe M.C., Chatfield G.F., “On Improving the Accuracy of the Simulation of Reciprocating Engines”, IMechE Conference, London, November 1-2, 2000, C587/001/2000, p.27-43.
BlairG.P., McConnellJ.H., “Unsteady Gas Flow Through a Four-Stroke Cycle Motorcycle Engine”, SAE Farm, Construction and Industrial Machinery Meeting, Milwaukee, Wisconsin, September1974, SAE Paper No.740736, pp20.
Blair G.P., “Correlation of Measured and Calculated Performance Characteristics of Motorcycle Engines”, Funfe Zweiradtagung, Technische Universität, Graz, Austria, 22-23 April 1993, p5-16
OPTIMUM Power Technology, Bridgeville, PA, PTRAN pressure trace analysis software, viz. Internet at optimum-power.com.
Blair G.P., Callender E., Mackey D.O., “Maps of Discharge Coefficients for Valves, Ports and Throttles”, Small Engine Technology Conference, Pisa, November 2001.
Wallace F.J., Boxer G., “Wave Action in Diffusers for Exhaust-Pipe Systems, with Special Reference to the Scavenging of Two-Stroke Engines”, Proc. I.Mech.E, vol.170, no. 39, p.1131, 1956.
Watanabe I., “Effect of Exhaust Pipe System on Performance Characteristics of Two-Stroke Diesel Engines”, Transactions SAE, 367B, 1961.
Purchase more technical papers and save! With TechSelect,
you decide what SAE Technical Papers you need, when you need them, and how much you want to pay.
Learn more >
*The appropriate SAE Member discount will be applied through the Shopping Cart process. Discounts vary according to level of membership:
Elite Member 20% Premium Member 15% Classic Member 10%
