Compression Tester Orifice

[cardo0]

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[Eric Page]

...crank up the supply pressure to 80psi or 85psi or whatever you use.

Just a note that Rotax specifies using a pressure of 6 bar for testing, which equates to 87 psi. This is often missed by mechanics/operators who are used to the Lycoming and Continental world where 80 psi is the norm.

[cardo0]

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[cardo0]

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[exftrplt]

Gentlemen, please accept my apologies for my lack of clarity. There are orifices and there are orifices. There is the orifice that is in the flow when the compression test is being performed. The size of this orifice is either .040" or .060" depending on bore size. These sizes were determined shortly after WW2 and not the subject of my question. Although how these sizes were determined would be interesting to know. My question concerned the orifice that Continental calls a "Master Orifice". Continental calls the first or in use orifice a "restrictor orifice". The little that I can find says the master orifice size also is .040",but I am not sure what orifice they are talking about. Incidentally as I understand it the use of master orifice to determine "allowable" leakage is only applicable to Continental engines. In any event, the question is, how was the size determined.