Altitude compensating TSIO-520 -- fuel flow behavior?

[whitepines]

A few quick questions for anyone else flying or maintaining altitude compensating TSIO-520s, especially the RAM VII engines -- trying to figure out what's normal vs. possibly a setup or regulator issue...

1.) On both engines, somewhere beyond around 30" MP (this varies engine to engine) the fuel flows (yes, I know, technically fuel pressure measured at the spider) increase significantly, almost in a stepwise fashion. I'm assuming this is by design in the mixture control unit / barometric compensator? The fuel flow increases smoothly with manifold pressure above and below that "step" region. Just curious if this quirk is unique to our engines or not.

2.) Has anyone seen evidence of sustained rich operation (e.g. deposits on their plugs) when these engines are operated in cruise at normal (78%) power IAW RAM's leaning charts?

3.) Any issues with the regulator consistently putting out too little fuel / lean operation (high EGTs) when below ~30" MP despite proper adjustment IAW Contenental procedures?

Any experience / anecdotes would be helpful, at least to potentially avoid the parts cannon troubleshooting approach!

 

[yamashill]

1. Does your RAM VII really not have a Shadin fuel flow or other EIS that actually does measure flow? I know that the top half of my throttle action only adjusts MAP about 8", The bottom half feels much more sensitive.
2. We run 65% with RAM VI IAW their fuel chart and have noted lead deposits on pistons, but not bad fouling with fine wire plugs.
3. The procedures provide a range of 5.5-6.5 at 600 RPM (RAM might provide slightly different numbers for the RAM VII). It sounds like the Unmetered Fuel Pressure was set to the high side of acceptable. Lowering the unmetered fuel pressure at idle AND THEN properly adjusting the idle mixture will allow for richer fuel flows at partial power.
Your A&P should be familiar with the following: "NOTE: Maximum part throttle full rich fuel flow will be achieved by setting the idle rpm (low) unmetered fuel pump pressure to the minimum value specified."