All you have to do is COPY an existing engine that matches the power curve and weight to your target machine as closely as what is already available.
Once duplicated, rename the engine, and then edit the "new" engine.
Change it's weight to match your new engine and muffler.
Adjust the power curve according to how your engine behaves.
Hint: The engine manuals show you maxium power output at specific RPM's.
Most engines drop off rather quickly after this and limit the maximum RPM's...
So if your engine has a max RPM of say 12,000, set two more data points, say one at 12,800 with half the power output at 12,000, and another at say 13,200 with ZERO power output.
That prevents the modeled engine from reving more than what the actual one would.
HP can be converted to the G3 torque/OZ using any on line calculators.
Finally cross check your prop size...
With your new engine selected, dial in a prop that matches the recommended for your engine.
Push the throttle all the way up.
Now observe the output HP in the editor.
Change the pitch and prop size until you get optimum output, then back down a few points (that's the power "reserve" you'll need).
That's it.
It's quite easy to make new "engines" in G3.
