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MSFS20 Need help adjusting C172 Engine / Propeller

A

Alexismmef

Messages
15
Country
portugal
Hey guys,

It's my first time tweaking a Piston Engine in FS. I have been trying to get the Default C172 to behave as close as possible to the Performance and Numbers.

The issue I'm having now is with RPM. If I adjust Engine Efficiency for Proper % of BHP for the Manifold Pressure, I can't adjust the RPM to match the real C172.

For ex. For MP of 23", The Manual says at 2000 feet, I should be getting 131 HP 73% of BHP. I adjusted that with Engine Efficiency. Now, my Engine Friction is set to 0.12, I believe that's the proper attribute to control how much RPM will be transfered from the Engine to the Prop on a Fixed Pitch Prop? I can't get more than 2400rpm. I should be getting 2500. Even if I increase throttle to full power, I'm always limited to 131HP, and can't get more RPM.

I also adjusted the Propeller Efficiency based on a chart I found on the internet, for a real study.
===================

engine_mechanical_efficiency_table = 0:1.0, 700:1.0, 2000:0.485, 2400:0.485, 2500:0.42, 2700:0.40, 2800:0.35

engine_friction_table = -300:-25, 300:0, 500:12, 2400:12, 2700:12

prop_efficiency_table = 19.0:0.00:0.10:0.10:0.15:0.20:0.37:0.30:0.55:0.40:0.68:0.50:0.76:0.60:0.82:0.70:0.83:0.80:0.77:0.90:0.57:1.00:0

prop_power_cf = 19.0:0.00:0.00:0.10:0.00:0.20:0.00:0.30:0.00:0.40:0.00:0.50:0.00:0.60:0.00:0.70:0.00:0.80:0.00:0.90:0.00:1.00:0

===========================
I tried messing with this Prop_Power_CF, but I didnt notice any change? Or maybe I'm doing it all wrong? The SDK for P3D also didn't help me on this :/ Anyone could give me a hand?

Thanks!
 
It seems, I can even delete the prop_efficiency_table = and prop_power_cf = tables from the Engine.cfg, and nothing changes, and the aircraft still flies fine? So, it seems MSFS2020 is not considering them, using a Built In Generic Table for all Props instead? If so, I hope they change it in the future.

I can't adjust the RPM for the HP being generated on a Fixed Pitch Prop, if I increase one, the other increase, lower one, the other decreases, it's always tied?
 
Found out how to be able to use the Propeller Tables. You have do add "prop_uselegacytables = 1" under the PROPELLER section.

Now, one issue I'm having is how MSFS is calculating Advance Ratio. It seems it's starting at 0.30, even when t he C172 is stopped, and as soon as it starts moving, it goes fast to 0.60/0.70, making the Propeller way more efficient than it should be during Takeoff Run. And this causes makes my C172 achieve Speed in 500ft, when should be more like 900ft..
 
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