Throttle Control Dead Zones

Actually, that perfectly describes what I am feeling.  I did check the cable and butterfly movement and it was very smooth.  I also watched the TPS and it seems that at nearly full open throttle the butterfly movement is less consequential than the TPS position.  You can actually feel the engine surge ahead as the mixture moves to full rich. Thanks for the response.  

A 100-300 rpm increase as the ECM comes out of ECO mode at 97% throttle (~5500) is normal.

If your engine is coming out of ECO mode at 5100 rpm your 97% throttle point is indicating that you are lugging the engine.

At a normal straight and level cruise at local pattern altitude, are you able to reach 5800 or beyond or at least very close?  (5750?)

At some point in the flight envelope, (Cruise or Climb) you should be able to make 5800 rpm.  

If not, you are never utilizing the engine to its full potential.

You may be saying what's the big deal?  It is only a few horsepower and the plane has plenty to spare.

If you haven't already, one day maybe years from now, maybe next week, you are going to experience a Density altitude event.

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Mine happened after a touch and go after burning off over half the tank of fuel.

We had been flying for 2+ hours of local airport hopping making half a dozen landing so far that day.

We weren't overweight by a long shot.  We were oblivious and fully confident.

What changed was the afternoon heat was peaking.

After finding ourselves still below the treetops, 3/4 of a mile beyond the runway, the cooler cornfields and very light inputs to the controls eventually resulted in a 50 fpm climb at MAX Power, Slightly leaned, and the smallest touch of Flaps.  Not a fun event!!!

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The difference in an engine peaking at 5400 rpm and 5800 rpm may only be a few horsepower, but one day it may be the difference between climbing out at a marginal 20 fpm and sinking into the trees at 20 fpm.

Don't throw away the top few horsepower because you think you will never need it.  Some day you will.

My G3X has an ECO mode indicator flag next to the manifold pressure gauge, but I have never taken notice of what RPM this changes.  I have only had this airplane a few months so I’m still learning those details, but I’ll take notice next flight.  I have attached a graph from the 912is pilot guide, and going by this it looks like the switch from Eco to Power mode happens almost exactly at 5100 RPM in cruise flight. I don’t think the relationship between throttle Position and Power is linear, and I believe the last 3% of throttle position represents a larger percentage of the power band.  

I have a problem with that example.  While it is educational, I do not take it as the final word.

It is an example of a prop that is optimized for max cruising flight (Racing).

Is shows an engine that only reaches 5000 rpm at the start of the ground roll and peaks at 5500 rpm during an assumed Vy climb.

The plane is then throttled back and leveled out to gain speed at a reduced rpm in the 4500-5000 rpm range.  It is Over-Propped!!!

Continuous operation below 5000 rpm is not recommended.

The Lower Flight Prop Load Curve only reaches 5800 at Max Power at cruise.

This is fine if your intention is to run the at Max continuous power during cruise where getting somewhere in a hurry is the driving force.

If you intend to throttle back and at least watch the Roses go by, then cruise optimization is not what you want.

If the chart was shifted over 300 rpm, the engine would peak in the climb and Overspeed if not throttled back when leveling off which is what most everyone does after reaching 1000 ft AGL because your 5-minute limit is approaching.

If you ever were to NEED Maximum Power, it is going to be when you absolutely NEED to clear the top of something in a hurry.

It is my opinion that the Engine/Prop combination should be optimized for Max Climb performance, not Cruise or some compromise in between.

That is, unless you are intending on running the plane at Reno!

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Now I need to go and put on my Flak-Jacket!!!

One interesting thing is that Rotax does not provide two different Eco/Power mode charts for the 912is and the 912is Sport engines, but they do provide two different power charts. I have the Sport engine which does have a different power curve. The sport model develops a higher max torque earlier, 130 Nm at 4800 RPM, whereas the standard 912is develops its max torque of about 120 Nm at 5400 RPM.  Power Curves (kW) are more similar but the sport engine kW output is bias towards the lower RPM.  All that said, I’m more interested in climb performance than another couple knots of air speed so I do plan to experiment with a lower pitch prop setting.