Engine Sound 'Flat Zone' Problem? How to Adjust...

[Lionheart]

Hey all,


As we all know, this is a huge hangout for Developers as well as Sim Enthusiasts. I have a question concerning engine tuning that the pro sites havent been able to figure out, so I thought I would ask the question here...


I have this plane which has a 'flat spot' in the engine sound. When you are between 45% and 100% throttle, the sound is the same, no change of pitch. With normal planes, your sound begins to change when moving off of full throttle, all throughout the throttle ranges, down to zero throttle. However, on this plane, the sound has this HUGE flat zone or plateau where it goes straight to the 100% sound throttle zone at roughly 40 to 45% throttle.

What would do this? What would cause this?


I know its not the sound config file or sound set, as I can rename it, and drop another sound file set in, like the Cessna 172 and it too has the same sound plateau issue. So its not a sound config problem.

I have looked in the AIR file to see if there was a throttle alignment entry and didnt find one. (Could I have missed it?). I have tried playing with engine settings in the config file for it, and that did no good.

The airfile template set for the aircraft is the Piper Cub base templates. I have modified the airfiles into the present Witmann Tailwind airfiles, which is a much faster plane, so the engine cubic inches was increased and 2 cylinders were added to the engine section to allow the power to bring the craft up to the proper speed of 200 MPH max. I am thinking therein may lay the issue.


I have seen this once before when I created the Aeronca LC. It created the same issue when I had adjusted the engine section. I ended up having to redo the configs over again to get the sound working right. On the Tailwind though, I dare not redo the entire set, as the settings are very 'right on'. But I could certainly redo the engine section.


Any idea's? I would be very curious to know. This is really a wierd problem and has had me at witts end for weeks now.

EDIT: NOTE; This is a fixed prop, and the original templates are for a fixed prop as well, so no changes there either.

Bill

[Lionheart]

This is the engine/prop section from the config;



[GeneralEngineData]
engine_type = 0 //0=Piston, 1=Jet, 2=None, 3=Helo-Turbine, 4=Rocket, 5=Turboprop
Engine.0 = 5.8, 0.0, 0.0 //(feet) longitudinal, lateral, vertical distance from reference datum
fuel_flow_scalar= 0.68 //Fuel flow scalar
min_throttle_limit = 0.0 //Minimum percent throttle. Generally negative for turbine reverser

[piston_engine]
power_scalar = 1.0 //Piston power scalar
cylinder_displacement= 80.75 //Cubic inches per cylinder
compression_ratio= 7.5 //Compression ratio
number_of_cylinders=6 //Number of cylinders
max_rated_rpm= 2300 //Max rated RPM
max_rated_hp= 65 //Max rated HP
fuel_metering_type= 2 //0=Fuel Injected, 1=Gravity Carburetor, 2=Aerobatic Carburetor
cooling_type= 0 //0=Cooling type Air, 1=Cooling type Liquid
normalized_starter_torque= 0.5 //Starter torque factor
turbocharged= 0 //Is it turbocharged? 0=FALSE, 1=TRUE
max_design_mp= 0 //Max design manifold pressure, (inHg)
min_design_mp= 0 //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= 0 //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

[propeller]
thrust_scalar = 0.6 //Propeller thrust scalar
propeller_type= 1 //0=Constant Speed, 1=Fixed Pitch
propeller_diameter= 6.0 //Propeller Diameter, (feet)
propeller_blades= 2 //Number of propeller blades
propeller_moi= 3.78 //Propeller moment of inertia
beta_max= 0 //Maximum blade pitch angle for constant speed prop, (degrees)
beta_min= 0 //Minimum blade pitch angle for constant speed prop, (degrees)
min_gov_rpm= 0 //Miminum governed RPM
prop_tc= 0.1 //Prop time-constant
gear_reduction_ratio= 1.0 //Propeller gear reduction ratio
fixed_pitch_beta= 30.75 //Fixed pitch angle of fixed pitch prop, (degrees)
low_speed_theory_limit= 80 //Speed at which low speed theory becomes blended in (feet/second)
prop_sync_available= 0 //Prop synchronization available? 0=FALSE, 1=TRUE
prop_deice_available= 0 //Prop de-icing available? 0=FALSE, 1=TRUE
prop_feathering_available= 0 //Prop feathering available? 0=FALSE, 1=TRUE
prop_auto_feathering_available= 0 //Prop auto-feathering available? 0=FALSE, 1=TRUE
min_rpm_for_feather= 0 //Minimum RPM for prop feathering
beta_feather= 0 //Feathering pitch angle (degrees)
power_absorbed_cf= 0 //Coefficient of friction for power absorbed by propeller in feather
defeathering_accumulators_available= 0 //Defeathering accumulators available? 0=FALSE, 1=TRUE
prop_reverse_available= 0 //Prop reverse available? 0=FALSE, 1=TRUE
minimum_on_ground_beta= 0 //Miminum pitch angle on ground, (degrees)
minimum_reverse_beta= 0 //Minimum pitch angle in reverse, (degrees)

[Lionheart]

I cross referenced this to the Cessna 172 config file and didnt find anything that really stood out....

[Lionheart]

Yep...

Man, no one knows this one. How did I do this??? lol....

[Roger]

I've never investigated this but perhaps a look at the mechanism that pulls in each wav file to denote the next higher pitch sound as the throttle is increased?

[Mathias]

Maybe a sound.cfg issue?
I'd check the engine's rparam and vparam sections.

[Marvin Carter]

Could be a rpm trigger for next wave. Hi Mathias!!!

[Rezabrya]

I am completely clueless in this area of FS but I will add some input in this. If you think everything else is right with the aircraft.cfg and the sound.cfg and everything, my guess would be that the problem lies in the fact that you used a much much less powered plane's cfg and fit it into the Tailwind cfg. Like I said I know absolutely nothing here but that sure sounds like it might bring up some problems... Maybe the cubs 100% throttle is the Tailwind's 45% throttle and that is causing the huge flat zone? I have no idea but I would sure look into that. On another note, I took some pics of a few Kodiak's and Tailwind's up here at Oshkosh and will share them once I get back. The Tailwind sure is a small zippy little thing. Both of the ones I took pictures of had completely tinted windows. Good luck figuring this one out.

[Lionheart]

I am completely clueless in this area of FS but I will add some input in this. If you think everything else is right with the aircraft.cfg and the sound.cfg and everything, my guess would be that the problem lies in the fact that you used a much much less powered plane's cfg and fit it into the Tailwind cfg. Like I said I know absolutely nothing here but that sure sounds like it might bring up some problems... Maybe the cubs 100% throttle is the Tailwind's 45% throttle and that is causing the huge flat zone? I have no idea but I would sure look into that. On another note, I took some pics of a few Kodiak's and Tailwind's up here at Oshkosh and will share them once I get back. The Tailwind sure is a small zippy little thing. Both of the ones I took pictures of had completely tinted windows. Good luck figuring this one out.


Hey Raptor,

That does sound possible. I will look for throttle clues.

You lucky person! Oshkosh! Have fun up there.


Bill

[dcc]

also you might confirm that the engine at max power is producing the value set in max_rated_rpm. (That setting only coordinates the sound playback envelopes to the engine power curve, it does nothing to the actual engine power) If the flight model is generating a different max power than set in that parameter, it could cause the sound to flatten out as you described.

- dcc

[Silver Fox]

Just guessing... But I would suggest that your 484 cu. in. engine is quickly winding up that 6 foot 2-blade toothpick of a prop to max rpm.

Quick test would be to change the number of blades and see if that changes the way the sound reacts.

Remember to post the solution. :)

[Roy]

I found by changing the max_rated_hp=65 to 185 in the cfg fixes the
flat zone.

[Lionheart]

I found by changing the max_rated_hp=65 to 185 in the cfg fixes the
flat zone.

I tried that and it made no difference. I will try it again. Thanks Roy.



Just guessing... But I would suggest that your 484 cu. in. engine is quickly winding up that 6 foot 2-blade toothpick of a prop to max rpm.

Silver Fox

I wouldnt have thought that having a V-12 in it would have made a difference.

[Lionheart]

Roy,

Still no joy.. Didnt make a difference on the HP rating. I tried moving the RPM Max Range also, along with the HP and that also did nothing. (I actually did that the other day, but... I didnt try them all together as a single tune test).


Bill

[Roy]

Bill,try 250hp with the defualt Maule sound.This is all i changed with
the Tailwind cfg.There is a i nice transition with the sound.I have
used other sounds and they all work ok.
Funny how this works for me and not for you.

cheers
Roy

[Lionheart]

Bill,try 250hp with the defualt Maule sound.This is all i changed with
the Tailwind cfg.There is a i nice transition with the sound.I have
used other sounds and they all work ok.
Funny how this works for me and not for you.

cheers
Roy


Roy,

I tried that and it at 250 HP and it indeed worked! A thousand thanks Sir!



Bill

[Roy]

Cool--it's a work around,mybe prop and hp combination problem.

Roy

[Lionheart]

I had thought that HP did nothing for the aircraft. It does nothing for airspeed. It does though, evidently tie into the sound files. Perhaps there is an equasion used for cubic inches/max RPM to get HP

At least the sound is working proper now. A great find. One that has had me at an impass for years on why or how that happens.



Bill