Van's Air Force
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G3 Percent Power
- Thread starter rv6ejguy
- Start date
KatanaPilot
Well Known Member
Not entirely sure but it seems to be based on the engine info you enter (displacement and horsepower) then it tracks fuel flow. You can leave rpm and throttle fixed but if you lean, the percent power drops. I wish it were more customizable. I don?t find it very useful, but maybe I?m just ignorant on how to use it.
The G3X guys watch these forums closely but you may want to email [email protected]. They're very good at responding.
I don't own one but was up test flying in a -10 today and didn't see repeatable results with TAS, and the same indicated % power at WOT LOP and part throttle ROP, same MAP, same RPM, same altitude.
Are there any items which maybe we don't have configured correctly on this one?
I am no expert on the system so would like to learn more.
Timberwolf
Well Known Member
Fuel flow plays a big part. In the initial setup you enter the engine horsepower. I believe from there they use generic tables to calculate based off MP, RPM, and FF. Altering any of these 3 will affect the % power. Also note in the setup it asks for HP @ XX“ hg to also account for boosted engines.
KatanaPilot
Well Known Member
G3X installation Manual page 34-133
Excerpt -
Engine Power
Estimated engine power can be calculated for Lycoming and Continental engines, using inputs from RPM, manifold pressure, and fuel flow sensors (all three all required for engine power calculation).
On the Engine Power Configuration page, select the appropriate engine type (Lycoming or Continental, turbocharged or normally-aspirated). Then enter the engine's maximum rated power and RPM (for example, 180 horsepower at 2750 RPM). For a turbocharged engine, enter the manifold pressure for maximum rated power. Configuring maximum manifold pressure is not required for a normally-aspirated engine, as it is assumed to produce maximum power at sea level pressure.
Excerpt -
Engine Power
Estimated engine power can be calculated for Lycoming and Continental engines, using inputs from RPM, manifold pressure, and fuel flow sensors (all three all required for engine power calculation).
On the Engine Power Configuration page, select the appropriate engine type (Lycoming or Continental, turbocharged or normally-aspirated). Then enter the engine's maximum rated power and RPM (for example, 180 horsepower at 2750 RPM). For a turbocharged engine, enter the manifold pressure for maximum rated power. Configuring maximum manifold pressure is not required for a normally-aspirated engine, as it is assumed to produce maximum power at sea level pressure.
Ok, thanks, they call it Estimated Power. I didn't search that term in the manual. I don't see baro taken into account here but perhaps they do. I wonder how fuel flow is worked into the equation here? Does % estimated power also drop off on the rich side of say 12.5 AFR? I'll have to pay more attention on the next flight.
What got me interested today was were were trying to gather some FF numbers vs. TAS at WOT LOP and then at the same % power ROP and throttled to the same % power to validate the premise that WOT has lower pumping losses and should give lower fuel flows.
We observed that TAS was not the same however at the same % power which put into question the accuracy of that data being displayed.
Anyway, more experimentation and data collection is called for. Love this stuff.
