Water inj, WEP and Afterburner...who can please shed some light???

[Guest saturno_v]

There is something I do no understand about how FS9 models WEP, Water Injection and afterburners.I searched the SDK left and right with no clarification in sight.I will try to explain what I mean by examplesJETSFor example, in the aircraft.cfg of Kirk Ollson's F-16 is specified a static thrust of 14300 lbs in the TurbineEngineData.This is, roughly, the amount of thrust in the real F-16 engine, dry with no afterburner.The aircraft.cfg mention only that the afterburner is available but is doesn't specified the amount od additional thrust delivereb by the AB.The same thing apply to the Alphasim F-4 and other military jets...the static thrust value in the aircraft.cfg is always the dry value without AB.How FS calculate the correct amount of thrust in AB conditions?? It does some sort of internal automatic calculation in the .air file??? With no need of additional info??As far as I know the percentage of thrust augmentation in Ab condition can greatly vary depending on the specific engine. The static thrust value of the aircraft.cfg is just an informational field that has no effect on the performance of the engine whatsoever??At this point I'm not interested how accurate or precise FS is..just trying to understand how it worksPISTON ENGINEA similar situation apply hereWhen the WEP or water injection is used, the max_rated_hp value of the [piston_engine] section of aircraft.cfg is for "dry" power. There is specified the type of emergency boost and the boost MP offset and the gain offset but not the amount of max power generated with the water injectionSo even here, the max_rated_hp value is just an informational field??The final power setting is just a calculated value inside the .air file or dinamically as the plane fly???I know that you can fine tune the values using the XXX_scalar fields but I'm interested in knowing how the logic works in general.... For example this is what I found in the aircraft.cfg section of David Copley's Lockheed P-38[piston_engine]power_scalar=1.00cylinder_displacement= 142.500compression_ratio= 6.650number_of_cylinders= 12number_of_magnetos=2max_rated_rpm= 3000.000max_rated_hp= 1500.000 //(this setting really only coodinates engine sound playback rate envelope with max hp), in this case max hp at wep is 1725 and max normal is 1425 -- so I've set it at 1500 to achieve my desrired rate envelope for the normal range and an extra rate increase for the jump to 1725fuel_metering_type= 2 // 0=Fuel Injected, 1=Gravity Carburetor, 2=Aerobatic Carburetorcooling_type= 1 // 0=air cooled, 1=liquid cooled.normalized_starter_torque= 0.020turbocharged= 1max_design_mp= 54.000min_design_mp= 9.500critical_altitude= 25500.000emergency_boost_type= 3 //none on early 38s (XP - G) emergency_boost_mp_offset= 6.000 //per spec, to get 60-inchesemergency_boost_gain_offset= 0.50 //adjusted so at 60 inches we get ~1600 bhpfuel_air_auto_mixture= 1auto_ignition= 0max_rpm_mechanical_efficiency_scalar=1.000idle_rpm_mechanical_efficiency_scalar=1.000max_rpm_friction_scalar=1.000idle_rpm_friction_scalar=1.000I honestly do not understand what he means in the commenst about the max_rated_hp and the comments in the emergency_boost subsection.So what is the power at max setting in this case, 1500, 1600 or 1725 HP???Thank you very mush in advance for your answersRegards

[Guest tango papa]

Military A/C have a stated HP rating for normal flight conditions, and another rating based on the enhancement used, afterburn for jets, WEP (War Emergency Power) for piston powered engines with water injection and/or turbo/supercharger at high altitudes. This extra kick-in-the-pants was used only for a limited time to prevent over stressing the engine, and there was only a limited amount of the water/alcohol for water injection. Water expands 18 times in volume from liquid to vapor, and helps to prevent overheating. Also, military A/C have certain requirements stated in contracts, for the minimum thrust/HP, and the contractors usually adds a safety margin in excess of the minimum. Part of the secret of success in life is to eat what you like -M.Twain

[Guest saturno_v]

I know very well how it works in real life ;-) Thanks anyway for the answer.I just would like to know how FS models AB and WEP...there is only one power/thrust field in the engine section...and developers usually use them for "dry" values.....how FS "knows" what the power/thrust output will be with AB or WEP?? It calculates it in a sort of standard way???I read somewhere that WEP duration is hard coded in FS to 312 sec.There is one example that I know where the maximum power with water injection is stated specifically in the engine section of the aircraft.cfg (with no emergency power boost specified)..it is the DC-6 by calclassic.....the dry and ADI power setting are modeled via gauges (ADI gauge and throttle gauge), probably to circumvent the 312 sec limit by FS.In this case, I suspect, the throttle gauge is modeled that if you do not have the ADI gauge "ON" you cannot reach full power even with your throttle all the way forward....and the ADI gauge has a counter that runs out at 18 minutes.I tried to change the power value on the default Cessna 172 aircraft.cfg to 20 hp instead of 180...well nothing happen..maybe now is even more "spirited" than usual....the only thing changed is that the full power engine sound is reached already when you barely move the throttle....how this works???