fs2004 air file- engine horsepower setup

[Blood_Hawk23]

First thing I see in the CFG is your entries need to be looked at. after the "=" you have spaces for some and no spaces for others. not sure if this matters but it might. I'm going to run them through a couple of programs and get some data. I'll post the pics provided I don't have any issues with my programs.

In the airfile is entry 509 needed? it refers to a turboprop.

1520- fuel injected?

turbo is still on in the airfile...

double check your fuel tanks for both air and cfg... they don't match



Thats just looking at it. not sure if any of it is the culprit or not.

 

[Blood_Hawk23]

try upping the compression ratio to 6:1

oh here is a little calculator for CID
http://www.mk5cortinaestate.co.uk/calculator2.php

I find it handy. alot better then doing the math by hand. I like to double check them from time to time. you'd be surprised how often its overlooked. your CID was fine.

General characteristicsType: 12-cylinder liquid-cooled 60-degree V
Bore: 4.5 in (114.3 mm)
Stroke: 6.0 in (152.4 mm)
Displacement: 1,145 cu in (18.8 liters)
Length: 56.75 in (1441 mm)
Width: 28.25 in (717.5 mm)
Height: 34.75 in (882.6 mm)
Dry weight: 693 lb (314 kg)
ComponentsCooling system: Liquid-cooled
PerformancePower output: 443 hp (330 kW) at 2,200 rpm
Compression ratio: 6:1

 

[Dev One]

I find that 509 is needed for piston engines to correct for the ideal HP generated by the fuel - you can see the effect if you run AFSD -
In fact the title says 'per cyl'.
Keith

 

[Blood_Hawk23]

it helps if you read the info and see that it mentioned both recip and TP. I removed the entry and ran it in airwrench. I see the effects now.

i turned off the turbo in the airfile. I also turned off 1520.

i added the min gov rpm of 575 to both the air and cfg. don't know how that will effect you. you might notice it on the ground. not sure where the number came from but airwrench had it there even though its wasn't in the airfile or cfg.

the data i'm seeing seems to be close to your desired numbers. I have one more program that I can run it all through.

have you checked the flight dynamics? you might have too much drag. just a thought.

 

[Dev One]

One thing I noticed when I was creating my Miles M13 Hobby, was that the flight reports noted that the manifold pressure was positive 1 psi @ 1000' - this was obviously due to the position of the carb intake, so I had to make the turbo active but at a low pressure. Normal 'boost' pressure in FS for a non turbo engine is always negative. Just a thought.
As for range/fuel consumption - do you know at what altitude they flew for best range? That can make quite a difference.
Just been fiddling my values for my WIP Falcon six using both 508 & 509 as well as adjusting prop pitch & drag, to get fuel flow, HP, RPM & ASI near correct. Got to keep the altitude very low when checking all of these - keeping it above ground level gets interesting as well as trying to read all the parameters!
Keith

 

[MaddogK]

it helps if you read the info and see that it mentioned both recip and TP. I removed the entry and ran it in airwrench. I see the effects now.

i turned off the turbo in the airfile. I also turned off 1520.

i added the min gov rpm of 575 to both the air and cfg. don't know how that will effect you. you might notice it on the ground. not sure where the number came from but airwrench had it there even though its wasn't in the airfile or cfg.

the data i'm seeing seems to be close to your desired numbers. I have one more program that I can run it all through.

have you checked the flight dynamics? you might have too much drag. just a thought.

Hmm... well the turbo entry in the air file was set in that record when I was experimenting with adding a turbo late last week but I forgot to change it back when I removed the turbo from the CFG file. Supposedly FS9 overrides that setting in the air file with the CFG setting so I didn't think it critical to remove it at the time.

The compression of THAT particular engine in this aircraft is very specific- and set to the documented spec in the CFG file.

Fuel capacity in the air file is overridden by the CFG file (I'm told) but the documented performance is of a 75 gallon laden aircraft, 2 crew, and 2-220 lb bombs.

I'm unsure about the airframe drag, but it was stated many times in the docs I have that is was a very low drag aircraft, so I assumed a value slightly higher than the slipperiest aircraft at the time- the DH.88 Comet. (incidentally the value I started with was that of a DC-3). I think the value I'm currently using is somewhere between the two.

I imagine it's easier to lie to FS to get the proper performance but I'm trying to understand why the correct values don't work, so this is a re-learning experience for me as I haven't touched an air file in a few years. I've been working the prop tables for documented performance at wide open throttle so they should be pretty close, it's just that HP reported by AFSD at part throttle that drives me crazy as 1850 RPM cannot be used as a cruise setting with such a low HP value used by FS even tho it's historically accurate. There's NO possible way I'm going to get the expected range of 1750 miles @ WOT, and at service ceiling @ 1850 RPM I'll be lucky to remain airborne.

I guess I could overpower the engine to get the cruise HP desired, then gimp the WOT prop tables but I'm trying not to do that.

 

[Blood_Hawk23]

even airwrench gives conflicting results with regards to range. in it it gives less range at lower rpms. i think it could be the fixed prop. Maybe. it seems to be getting close to mach at the tip. i run an angle of 35 on my WWI ACs but all have this for the turbo

turbocharged= 1
max_design_mp= 29.000
min_design_mp= 12.000
critical_altitude= 100.000
emergency_boost_type= 0
emergency_boost_mp_offset= 0.000
emergency_boost_gain_offset= 0.540

here is what i run for my prop

[propeller]
propeller_type= 0
propeller_diameter= 9.000
propeller_blades= 2
propeller_moi= 12.697
beta_max= 35.000
beta_min= 35.000
min_gov_rpm= 600.000
prop_tc= 0.010
gear_reduction_ratio= 1.000
fixed_pitch_beta= 35.000
low_speed_theory_limit= 44.000

i haven't tried it on yours yet. it could make it worse for all i know. these are from my sopwith camel. other then prop dia all of my WWI ACs use the same. a few do have reduction gears.

i'm not sure how the other FS sims behave but cfs2 does some strage things with the airfile and cfg. In our case the player AC will use the entries that are in the cfg when they differ from the air file. but the AI it is the other way around. so you may never see the difference if it is a player only AC. there might not be any. just a thought.

i'm back to work for the next four nights. I hope that your able to figure it out.

Till Later,
John

 

[MaddogK]

even airwrench gives conflicting results with regards to range. in it it gives less range at lower rpms. i think it could be the fixed prop. Maybe. it seems to be getting close to mach at the tip. i run an angle of 35 on my WWI ACs but all have this for the turbo

turbocharged= 1
max_design_mp= 29.000
min_design_mp= 12.000
critical_altitude= 100.000
emergency_boost_type= 0
emergency_boost_mp_offset= 0.000
emergency_boost_gain_offset= 0.540

here is what i run for my prop

[propeller]
propeller_type= 0
propeller_diameter= 9.000
propeller_blades= 2
propeller_moi= 12.697
beta_max= 35.000
beta_min= 35.000
min_gov_rpm= 600.000
prop_tc= 0.010
gear_reduction_ratio= 1.000
fixed_pitch_beta= 35.000
low_speed_theory_limit= 44.000

i haven't tried it on yours yet. it could make it worse for all i know. these are from my sopwith camel. other then prop dia all of my WWI ACs use the same. a few do have reduction gears.

i'm not sure how the other FS sims behave but cfs2 does some strage things with the airfile and cfg. In our case the player AC will use the entries that are in the cfg when they differ from the air file. but the AI it is the other way around. so you may never see the difference if it is a player only AC. there might not be any. just a thought.

i'm back to work for the next four nights. I hope that your able to figure it out.

Till Later,
John

Between the two calculators you linked to earlier I'm able to plot out the speed/RPM curve I expect, and using the known formula for calculating the FS9 'J' value I plotted the expected values as well only to discover the range of 'J' from 108MPH to 156MPH to be less than .015, so with 156MPH @ 2300 being right on the money no amount of prop table tweeking is going to get me 125MPH @ 1850 RPM because manifold pressure is just too low @ 1850 to generate the expected 380HP.

I need to figure out how manifold pressure is calculated, THEN I might be able to get that elusive cruise speed setting to work right. Looks like I'm doomed to lie to FS9 and install a supercharger (the turbo is too weak), use wrong displacement and compression numbers, or something even more radical.


Aww carp, this is how I started my journey but somehow talked my way out of it.
http://www.fsdeveloper.com/forum/threads/rpm-vs-hp-for-piston-engine.18243/

 

[Dev One]

By playing even further with table 511, you can get aerodynamic braking when closing the throttle!
For any J value above .95 with a positive efficiency value needs to be made negative - I've used -2.0 - & I've found that for my WIP aircraft that closing the throttle at 160 MPH (cruise speed) to the flaps operating speed of 100MPH, before modification took 55 - 60 seconds in level flight.
After modification this reduced to 25 seconds. This value was suggested after I queried a real pilot with a 172 in a forum question elsewhere at SOH.
I have also amended the curves lower down to get a better HP value & rpm during stationary run up & during take off. Fuel consumption also nearer the mark at cruise. Cruise drag value also tweaked to balance things out.

Keep fiddling, you will get there, although probably with less hair!
Keith

 

[MaddogK]

By playing even further with table 511, you can get aerodynamic braking when closing the throttle! For any J value above .95 with a positive efficiency value needs to be made negative - I've used -2.0 - & I've found that for my WIP aircraft that closing the throttle at 160 MPH (cruise speed) to the flaps operating speed of 100MPH, before modification took 55 - 60 seconds in level flight. After modification this reduced to 25 seconds. This value was suggested after I queried a real pilot with a 172 in a forum question elsewhere at SOH. I have also amended the curves lower down to get a better HP value & rpm during stationary run up & during take off. Fuel consumption also nearer the mark at cruise. Cruise drag value also tweaked to balance things out. Keep fiddling, you will get there, although probably with less hair! Keith

Hmmm... Table 506. According to AAM "Affects manifold pressure. Sets throttle Idle stop and max MP wrt Induction Flow" It has 2 points creating a flat, linear 'curve'. I wonder...1 axis has got to be the throttle position but I'll bet the other is the induction flow percentage. Would be interesting to see if it'll work with more than 2 points in the graph.

EDIT : WOW, I'm onto something here. Adding a 3rd point in 506 lets me redefine the throttle curve, and 'fattening up' the low to mid range got me 12 MPH @ 1850 RPM over the untouched 506 curve. I also noticed my 'J' value has shifted -.15 across the board which it should do. I think Jerry's equation is missing a variable. My top speed hasn't changed but the low RPM power range has definitely been improved.

 

[Dev One]

Nice find - thanks for the idea, I will have to try it as I don't have it on my simplified listing.
Keith

 

[Blood_Hawk23]

sounds like your making progress.

here is an article to check out. It may have something usefull.

http://www.advancedpilot.com/downloads/prep.pdf

 

[MaddogK]

Nice find - thanks for the idea, I will have to try it as I don't have it on my simplified listing.
Keith

I stumbled on it by the description of the record in AAM, but it's probably not the best solution as I can't find any other aircraft in FS that has more than 2 points in this record, but the results are startling. I should however stress a small mistake in my above post about my shifted 'J' values, altering this record should NOT have altered the 'J' values in any way since 'J' is calculated strictly by RPM and A/C speed vs. prop diameter. I definitely have to look closer at this record or find the record that can alter 'boost gain'. I think I'll try inverting it to see what happens.

EDIT : EUREKA !!! Inverting 506 seems to have solved my dilemma- I've NOW got a MP of 21 @ 1850 RPM instead 10. My cruise speed 'magically' found itself just short of 5 MPH from where the docs say it should be. Now I can rework the numbers and hopefully get them to match the docs.

Thanks Blood_Hawk23, that IS an interesting doc. It's got some nice explanations of 'old school' tuning tricks we used to use on carburated engines before the computer management systems were widely used. I wish I had that chart of cylinder head temp vs. mixture years ago when trying to explain to a customer why their car ran like crap on the highway and why we had to rejet their carburator.

 

[Blood_Hawk23]

Well from one mechanic to another, your welcome. I hoped it has helped.

So the question now is has your range improved? The MP at 10 would explain alot. According to the doc it should have gone up atleast a little due to the slower RPM.

The trouble you've been having is why so many CFS2 designers use the stock AIR and CFG files. Very few can understand, let alone adjust the AIR files. It seems the Old programers GIGO (garbage in garbage out) still holds true. How were you able to change it?

If there is away to convert your AC to CFS2 I'd love to fly it.

 

[MaddogK]

Well from one mechanic to another, your welcome. I hoped it has helped. So the question now is has your range improved? The MP at 10 would explain alot. According to the doc it should have gone up atleast a little due to the slower RPM. The trouble you've been having is why so many CFS2 designers use the stock AIR and CFG files. Very few can understand, let alone adjust the AIR files. It seems the Old programers GIGO (garbage in garbage out) still holds true. How were you able to change it? If there is away to convert your AC to CFS2 I'd love to fly it.

As an old mechanic I couldn't understand why manifold pressure was so low at idle and mid range but assumed FS was doing some 'behind the scenes magic', now that I think about it 506 being inverted makes a little sense, the air file I used was a donor that had a turbo and would need it that way for as a turbo would make the man pressure go positive at higher RPM's- a naturally aspirated engine would never go positive while it's running. I would guess the reason why default NA FS9 A/C don't even have that record is because FS does assume it's own correct record 506 if it's missing. I changed it simply by using AAF (aircraft airfile manager) and transposing the 'Y' values from each end of the graph. Inserting the third point in the graph was done with Jerry Beckwith's Airupdate utility and notepad.

And YES, cruise range increased at least 100% simply because the engine is producing more torque to turn the prop at cruise setting, and part throttle airspeed increased 30%. Maximum airspeed is unaffected, and I would assume that climb rate and ceiling are also untouched as well but can't confirm that until I do some more testing after I tweek the prop tables some more. Since I'm rebuilding the visual model anyway I'll see what I can do to build a CFS2 version, but it's been at least 10 years since I've built anything for CFS2.

 

[Dev One]

506 is also listed in the templates within FS9 listing - I found it in the single engine HP template.
Interested in how you did the 3rd point insert though, so I will try doing it with Jerrys FDWB.
Keith

 

[MaddogK]

506 is also listed in the templates within FS9 listing - I found it in the single engine HP template.
Interested in how you did the 3rd point insert though, so I will try doing it with Jerrys FDWB.
Keith

It was pretty simple- using the utility just export as a txt file, edit into record 506 another X,Y coordinate and a value, save the txt file and re-run the utility to recompile the air file.

 

[fliger747]

A couple of comments:

Fixed pitch props are quite a bit more difficult to work with than constant speed props in setting up an FS engine as you have added an extra variable.

Older piston engines experienced a lot of delivered power loss at high we RPM values due to internal losses, lubrication slinging being one of the real culprits. Even the relatively late and sophisticated R2800 gained quite a bit more than 100 HP between the B and C series just due to an improved oil scavenging system, plus another useable 100 RPM. For FS piston engines the shape of the Friction per cylinder curve (wish there were more points) can be tuned to approximate the HP output ratio vrs RPM. Of course the fixed pitch prop curves make life extra exciting and the overall HP of the engine must be re adjusted.

Specific Fuel Consumption: A value of .49 would be low for an engine of this era as this was typical of WWII high performance engines. Modern general aviation engines tend to do a bit better with values somewhere around .43 lb/hr/hp or so. The R985 I am currently flying in the DHC Beaver relies quite a bit on mixture enrichment for cylinder cooling at higher power settings.

Not sure that a min governed RPM has any effect for a fixed pitch prop. Not that it should have too much effect, but wooden props tend to have low MOI values, the main reason they are not found much on gen av aircraft these days has to do with the constant maintenance required.

Fun Project! Cheers: Tom

 

[MaddogK]

A couple of comments:

Fixed pitch props are quite a bit more difficult to work with than constant speed props in setting up an FS engine as you have added an extra variable.

Older piston engines experienced a lot of delivered power loss at high we RPM values due to internal losses, lubrication slinging being one of the real culprits. Even the relatively late and sophisticated R2800 gained quite a bit more than 100 HP between the B and C series just due to an improved oil scavenging system, plus another useable 100 RPM. For FS piston engines the shape of the Friction per cylinder curve (wish there were more points) can be tuned to approximate the HP output ratio vrs RPM. Of course the fixed pitch prop curves make life extra exciting and the overall HP of the engine must be re adjusted.

Specific Fuel Consumption: A value of .49 would be low for an engine of this era as this was typical of WWII high performance engines. Modern general aviation engines tend to do a bit better with values somewhere around .43 lb/hr/hp or so. The R985 I am currently flying in the DHC Beaver relies quite a bit on mixture enrichment for cylinder cooling at higher power settings.

Not sure that a min governed RPM has any effect for a fixed pitch prop. Not that it should have too much effect, but wooden props tend to have low MOI values, the main reason they are not found much on gen av aircraft these days has to do with the constant maintenance required.

Fun Project! Cheers: Tom

Ya, the 'assumed' fuel consumption of FS9 is a bit low compared to the actual dyno data, but I can fix it with a scaler. Now that I've seen what I can get away with in the prop curves I'm pretty close to where the NACA data says I should be, and the rest I think I can guesstimate by the 'feeling' in-game. Oh, I can't even guess at the prop MOI as it was a forged aluminum prop- very cutting edge for it's time (only a couple years from it's patent date).

Who can actually point at me and say I'm outright wrong when dealing with a very limited number of 90 year old aircraft, but I'll take every criticizm under advisement. The previous model was RTW committee approved so it was pretty close, but after looking at it again a few years later all I can think of is "what was I thinking, this isn't even close".

 

[fliger747]

The aluminum props have a higher moment value but do have advantages where it comes to maintainance, durability and precision of manufacture. A friend has a wooden prop on her Pacer, but she, being and a&p plus IA, is willing to put up with the hassles for her specific application. Earlier engines suffered from les sophisticated carburation and exhaughst, poorer fuels etc, so a lower fuel efficiency would be expected. It was appreciated that extra rich mixture was beneficial for cooling and instrumentation was certainly not available to monitor much besides oil and coolant temperatures.

The RTW folks mostly look at top speed....

regards. Tom