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Cirrus GTS N122MG

The Gami lean test is used to determine the spread of peak EGT's as a function of fuel flow in order to determine whether Lean of Peak (LOP) operation is possible. For instructions on how to perform the lean test, see Gami Lean Test.  Basically you have to set yourself up in the cruise and slowly reduce the mixture control passing through the peak EGT's and noting the fuel flow for each EGT peak. For a perfectly tuned engine, the spread of fuel flows should equal zero. Generally values less than about 0.5 gallons per hour in fuel flow are acceptable. With aircraft having the Emax system, you can download the flight data during which you have carried out the test.

To work out the Gami spread, use the Emax analyzer to find in the EGT plot the region where you have passed through the EGT peaks. With the mouse you can zoom in on this region and plot the peak(s) so that on the right-hand side of the graph the EGT's have returned to constant values. Then using the Sherlock Homes button in the program, you will see the fuel flow plotted with the EGT's and the value of the Gami spread is given in  the opened blue box.

The above example shows a Gami spread of 0.8 gallons per hour, which is not particularly good. You can see in this example that EGT2 has peaked substantially before the other EGT's and so the fuel flow for peak EGT2 is considerably higher than for the other EGT's, which have all peaked together.  Below is another really nice example, showing effect of an injector problem on cylinders 5 and 6:

N122MG Gami Lean Test