Engine Tune causes arc in sound to falter

Hey all,

Adjusting engine tuning and performance caused my sound to stay at top end till about 75% throttle.

Can someone tell me the 'exact setting' that causes this? Is it possibly 'cubic inches' or horse power? Or could it be the two of them combined is not working on the math?

This is what I have so far on my engine specs. I am having to use one engine for both props, simulating a joined prop shaft safety system for both fans.

engine_type = 0 //0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
Engine.0 = 0.0, 0.0, 0.0 //(feet) longitudinal, lateral, vertical distance from reference datum
fuel_flow_scalar= 0.01 //Fuel flow scalar
min_throttle_limit = 0 //Minimum percent throttle. Generally negative for turbine reverser

// number_of_propellers // The number of propellers driven per engine.
// engine_map // Set of flags that allows the propellers to be driven by a different engine.
// propeller.0 // to propeller.1

power_scalar = 1.0 //Piston power scalar
cylinder_displacement= 90.3 //Cubic inches per cylinder
compression_ratio= 8.7 //Compression ratio
number_of_cylinders=16 //Number of cylinders
max_rated_rpm= 2700 //Max rated RPM
max_rated_hp= 300 //Max rated HP
fuel_metering_type= 0 //0=Fuel Injected, 1=Gravity Carburetor, 2=Aerobatic Carburetor
cooling_type= 0 //0=Cooling type Air, 1=Cooling type Liquid
normalized_starter_torque= 1.0 //Starter torque factor
turbocharged= 0 //Is it turbocharged? 0=FALSE, 1=TRUE
max_design_mp= 30 //Max design manifold pressure, (inHg)
min_design_mp= 15 //Min design manifold pressure, (inHg)
critical_altitude= 0 //Altitude to which the turbocharger will provide max design manifold pressure (feet)
emergency_boost_type= 0 //0=None, 1=Water Injection, 2=Methanol/Water injection, 3=War Emergency Power
emergency_boost_mp_offset= 0 //Additional manifold pressure supplied by emergency boost
emergency_boost_gain_offset= 0 //Multiplier on manifold pressure due to emergency boost
fuel_air_auto_mixture= 1 //Automixture available? 0=FALSE, 1=TRUE
auto_ignition= 0 //Auto-Ignition available? 0=FALSE, 1=TRUE
max_rpm_mechanical_efficiency_scalar= 1.0 //Scalar on maximum RPM mechanical efficiency
idle_rpm_mechanical_efficiency_scalar= 1.0 //Scalar on idle RPM mechanical efficiency
max_rpm_friction_scalar= 1.0 //Scalar on maximum RPM friction
idle_rpm_friction_scalar= 1.0 //Scalar on idle RPM friction
detonation_onset = 36


Resource contributor
Have you tried a different sound set?

It could be that the sound.cfg is not set up for your modified engine parameters.
The sections you should be looking at are "combustion.1.xx" and/or "prop.1.xx" and the "rparams" and "vparams" parameters in each.
Numbers for each parameter are posted in pairs (e.g. 0.0,0.05,0.25,0.1,...), with the first one being either percentage of max hp or rpm (e.g. 0.0, ..., 0.25,...) and the second one being sound pitch/speed or amplitude (e.g. ...,0.05, ..., 0.1, ...).
There can be multiple "combustion.x.y" sections, each being accessed by the section specified in the "link" parameter of the preceding section.
Ideally, each section covers an input value (i.e. hp or rpm) range from 0.0 to 1.0.

See if there are gaps or if output volume (maximum_volume) caps the generated amplitude.

That's about all I know about sound.cfgs.

The entire parameter list is available here:
Oddly, this is messed up when your HP and 'cubic inches of cylinders' is mis-matched. The cubic inches is what really gives the sim its knowledge of how much power you have, not the HP setting. So you just adjust the HP to the displacement and your scaler should then work properly.
I found this in the AAM descriptions of the various settings.
R505 Piston Engine,
Line-Engine Power Sound Level, (HP), 2700

Sets sound level to HP developed?
Displacement, No. Cyls, Torque tables, etc. set HP

That's one possibility for adjustment.

I seem to recall reading someplace, as well, that the only thing the Aircraft.cfg file, [piston_engine] section, either line cylinder_displacement= , or compression_ratio= , I can't recall which, had the same effect. No real change to the engine's HP, just to the sound.
But darned if I can find it now.

Hope this is of some small help...