2 stroke expansion chamber design program.   Free download here

This program calculates the dimensions for both double and triple stage diffuser expansion chambers from a few basic engine dimensions.  The information used in the program's calculations was taken from the books ‘The Basic Design of the Two Stroke Engine’ and ‘Design and Simulation of Two Stroke Engines’; both books are written by Professor G.P. Blair of Queens University Belfast, and published by the Society of Automotive Engineers.  You are well advised to read at least one of the books mentioned above, since they contain the author’s academic lifetime of knowledge on the two-stroke engine.

There are several coefficients used in the design of the expansion chamber – these are a function of the engine’s state of tune. Those used in this program  have been chosen for petrol engines and are in the range 50cc up to about 500cc per cylinder. It is doubtful these formulae would work on small capacity glowplug engines, since the exhaust gas temperature is much lower, and the engine speed is much higher.

This will get you started by providing, for your engine,  the dimensions of an expansion chamber with a 2-stage or 3-stage diffuser.   Free download here  . Of course the dimensions so provided could be inserted in a MOTA engine data file and MOTA-X then used to provide an optimum expansion chamber design for your engine over your choice of speed range.

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