I think this is because the engines have a simple compressor that kicks at certain point. So where in flight the throttles reach its maximum pressure (atmosferic) but if you push them a bit more the compressor starts working and you have a sudden increase of power
My understanding is that this behaviour is realistic in this type of planes with this type of engines.
Yes. I did also notice it,. No idea how to correct it. However in my install is not really severe.
Thank you for adressing this issue. I was not aware the plane if bought from the marketplace has its files encripted. This is what I have modify, but it only applies to the structure of the plane when bought from the web.
layout.json (in the folder wing42_boeing_247d)
Controls.xml (in the folder wing42_boeing_247d/ModelBehaviorDefs/wing42-boeing-247)
sound.xml (in the folder wing42_boeing_247d/SimObjects/Airplanes/wing42-boeing-247d/sound)
I also have added an extra file:
wing42_boeing_247d_ala13.pc.pck
I am going to try to learn how to make the mod work in the COMMUNITY folder as suggested. I am going today on holidays until the 27th. I will try to work on it then. Cheers.
I made a ready to use mod with your modifications; I can show you how if you want.
I really don’t like modifying base files or official plane files (especialy here with somethnig we might never be able to download anymore)
I would love to see a guide on how to do this. 
Yes, please. I can include also the fix for the oil pressure gauge and the changes in the indicator.
That would, maybe, make sense at higher altitudes, when not under a high enough load for boost to be produced by the supercharger, but when you’re on short final atmospheric pressure air density is high and throttle response below boost levels would be, as well.
I’m not understanding why this would be the case. Studying circuit diagrams of Bendix-Stromberg pressure carburetors fitted to P&W Wasp-series engines would indicate they are fitted with complex idle circuits.
Ok, I have just made the mod compatible with the Community fiolder and uploaded it 1 minute ago. Just unzip it and place it inside the community folder (as you normally do with mods). Please let me know how does it work and what do you think about the new sounds.
Fantastic!
It’s crazy to actually be hearing the right-side engine’s starter winding up after all this time.
I’m not up in the air yet, but am listening to these new engine sounds burbling at ~1000 RPM during warm-up.
I must offer my heartfelt congratulations and thanks for your efforts here. I’ve wanted to delve into making a couple of improvement mods to some of my favorite add-on aircraft and your efforts (and those of others) are really pushing me to make the effort.
EDIT:
Something a little odd has just happened. I raised the RPM to 1400 to hear what they sound like at a bit higher RPM. I then switched to an external view accidentally, and now I have this crazy sound phasing going on. It’s hard to tell, but I think it might be playing your sounds and the stock ones at the same time.
EDIT:
Here’s a link to video where you can hear it:
This is still a first version. That is why I included the original sounds (just replace the sound.xml in the mod and you will keep all modded sounds but the engine). I am aware of the fasing (in high rpm) still working to solve it. Keep tuned.
Again, good work here!
The instrument stutters annoying ant not innocent. They accompany a significant oil loss, which will eventually lead to running out of oil, overheating and engine seizure. Happened to me a lot, and I have been monitoring the oil quantity. My Copilot for B247D shows the amount of oil remaining.
Yes, this is the most annoying bug now, I realized that using your autopilot. Every time the instruments are doing something like a reset (going to full scale then to 0 and start working again) the oil quantity is reduced by aprox 30%. This prevents you from doing long trips.
Maybe someone can do a mod to be able to refill the oil tanks in flight… 
I’m not sure the instrument spazz event and oil loss are universally connected. I get the instrument and aircraft stutters/reset as well but I don’t see an accompanying oil loss, and I’m using the oil monitoring plug-in as well. I am generally not losing excessive oil on my typical 1-2 hour flights.
Whilst Capt. Redgrave is a complete idiot for repeatedly wondering why the oil pressure continued to drop to nearly zero when, after all, he had the oil shutters completely closed, managed to utilize the part of his brain that saved his bacon, and everyone on board, by his remarkable prowess in gliding the 247D to a mild, wheels down, landing on a farmer’s hillside field in a valley surrounded by high hills from 8500’.
OK, I had managed to identify both anoying sound issues. One was the phasing at high RPM. This is because I had replaced the engine sounds and not the propeller chop sound, so they do not share the same “pitch”. In my lto do list is the 1st item. I will replace the propeller chop sound with custom ones. In the meantime, if you find it annoying, just go to the section in the sound.xml and remove (or make it text) the section called <!-- Propeller chop --> (if you enclose that section with the label <!-- and --> that section becames text and is not considered code.
Also the sound you can hear when advancing the throttle and the RPM rise suddenly is due to the engine backfiring. The sound is awful and I will replace it with something more realistic. This is my item2 in the to do list. In the meantime you can remove it doing the same in the sound.xml I explained above, but with the section called <!-- backfires -->
The new 4.1 version has included the oil temperature fix, I have noticed the oil loss is linked somehow (not directly but it some extent) to running the engine with the oil at low temperature.
Also, not related to the sounds, the oil takes ages to heat, but just an small opening in the cowl flaps drops its temperature rapidly. Even if they are at the minimun. I do not know how realistic is this, but I am going to start fiddling with the engines.cfg to try to reduce the cooling efect of the cowl flaps so the cowling effect is more progressive.
The other day I tried your sound mod and liked it a lot. The only thing that put me off was the strong phasing sound. Once you’ve fixed that you will have brought the 247D back to life to me singlehandedly. It was mothballed for over a year now, because of the awful soundset which I simply couldn’t stand.
Thank you so much! Excellent work and also many thanks to Big Radials again for allowing you to use their engine sounds.
remove the phasing is very simple. Just do what I said in the post above. I am right now working in a more appropriate solution.
I’m confused by this. Do you mean the oil shutters? I didn’t think there were cowl flaps on this aircraft. (Which I always found interesting since most radials have them to maintain cylinder head temperature.)
Do you know if carb icing is actually modeled? The manual/clipboard speaks of maintaining 100°F carb temperatures, but I’ve never really seen anything happen in terms of carb icing when I’ve neglected this.
Thank you, again, for your work on keeping this aircraft alive. I really enjoyed your sound package on my last flight regardless of my embarrassing failings with the oil system.
yes, sorry. I mean the oil shutters. I have been flying the A20 yesterday and I had in mind the cowl flaps, as they are in the a20. B247 do not have cowl flaps, it has oil shutters.
I hope you can find a fix. I assumed this was all handled via wasm which we only get compiled. I’m not sure with all the custom fluid handling and calculations how much of the engines.cfg actually affects the temps.
Best luck to you, you are doing a great job!
