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.

[GeneralEngineData]

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

[piston_engine]

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