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MSFS Confused with Engine Model (engines.cfg)

Taz5150

Taz5150

Messages
63
Country
spain
Hey everyone,

When I though I had a reasonable understanding of how the engines are being modeled, I find myself bumping against a wall once and again. As has been discussed in several posts, the engines.cfg file now includes the 150x tables from legacy .air files, some variables from the legacy aircraft.cfg file and some other new variables/ parameters.

Having those tables, I though made it possible for us to use the theory and techniques we've all being working with for the past few years. But I was wrong. Not only the models do not behave at all with respect to those tables; if you delete all of them, the model behaves the same as if you have them (with whatever values). It also seems that the new curves are being characterized from the new low-high parameters within engines.cfg (i.e. low_idle_n1. high_n1, idle_FF, etc.).

All in all, I have been testing the A320Neo model at ISA conditions and a Sea Level airport.

  • Idle and Max TO (TOGA) values for N1, N2 and FF are taken from the new low-high variables within engines.cfg, not the table related variables.
  • One thing I tried was to tweak the tables to have idle and maximum n1, n2 and FF values just like the variables in engines.cfg. No joy. At different throttle levels the different parameters do not follow the tables.
  • Taking out ALL table related variables, but maintaining low-high variables, gives exactly the same output as with the Tables. Exception: Thrust is always 0. If we maintain ONLY the table that relates CN1 to Thrust, then we get thrust values back again (although the values do not follow the table).
  • Maintaining Tables, but deleting ALL low-high variables (N1, N2 and FF), actually messes up everything and engine parameters do not follow Tables:
    • N1 idles at 50%
    • N2 idles at 50%
    • FF idles at 16 Kg/h
So in conclusion due to my findings:

  1. Tables do not seem to be needed for engine modeling
  2. Low-high variables seem to be the ones being used to characterize engine behavior
  3. This would mean engine characterization is hardcoded and we are only allowed to give minimum and maximum values for them
Hope this helps out. Also, if anyone has any other experience or feedback, I'd appreciate a challenge to these findings.

Thanks!
 
Taz5150

Taz5150

Messages
63
Country
spain
Well, it seems (as I thought) I am not the first one coming to this conclusion...

forums.flightsimulator.com

DA40NG Climb / power issues

@jonasbeaver I have made a few edit on the engines.cfg but unfortunately we can’t tweak cf prop and prop efficiency curves. The corresponding entries in the cfg are used only by legacy FM. According Asobo, thrust efficiency and power absorbed are now constant curves common to all aircrafts, only...
forums.flightsimulator.com forums.flightsimulator.com

... although I haven’t found anywhere within the SDK info regarding legacy vs. modern engine data.
 
R

robert young

Messages
17
Country
unitedkingdom
I am finding exactly the same thing. I cannot get for example any piston twin to feather. Whatever parameters I tweak the feathering does not work, The props just keep rotating even at extremely slow (stall) speeds. In FSX feathering was far from perfect but it did work. There are some new params in the Asobo prop section: named "cx=". Does anyone know what these are?
 
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