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Showing results for tags 'Fuel Mixture'.
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I have a 1979 M20k with intercooler and Merlyn Wategate. I recently had the fuel pump and mixture controller replaced/overhauled. I've had 2 shops, including a Mooney service center, attempt to set up the fuel system. I get full rich at idle, 24gph full rich at full power, but as I reduce manifold pressure my TIT/EGTs rise. I usually get about 18gph at 2600/30in TIT 1350 in climb and now get about 15-16gph with TIT approaching 1500. In cruise I have to use full mixture to get 75 ROP and at low altitudes it is more like 50 ROP. This M20K has always been set rich - firewall mixture was over rich on take-off (more than 24gph) and I had to set fuel flow in run-up so I would be at about 24gph on take-off roll. The current shops are setting to the book. Initially one would say it is one of the replaced components, but I'm thinking this may be an issue that had previously been compensated for by this over rich setting. Has anyone seen this type on non-linearity in the fuel system such that you get full rich at idle and take-off but run best power or less flows in between (all cases firewall mixture)? One of the mechanics suggested that the Merlyn may be driving a higher MP than the mechanical fuel control is "expecting" below full power. Any thoughts?
