I realize it’s supposed to be lower, but 8”? That’s nearly 1/3 missing.
Standard atmospheric pressure at sea level with the engine off will always be “about 30” regardless of the type of engine.
So that isn’t relevant to the topic of what manifold pressure you should be able to hit with the throttle wide open.
@MajesticRain926 - thanks too from us for linking to Arrows Across America, its great to see it popping up on different threads. 
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i like to fly this a lot,thank´s 
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To understand the relation between manifold and RPM I suggest you read this post: Manifold Pressure vs. RPM: What's the Difference? - Pilot Institute
Th A75 has a constant pitch propeller and the recommended maximum value for this engine is 2300 RPM.
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I don’t think the Stearman came with a restrictor plate on the inlet. Naturally aspirated carbureted piston engines will achieve very near ambient pressure at WOT. It’s ambient minus intake losses which usually amount to a few tenths of an inch. Significant intake losses at WOT would require installation of a restrictor plate, and at the observed pressures - an aggressive one. Restrictor plate - Wikipedia
There are other ways in the sim to shave off some performance and hit book numbers that don’t impact your manifold pressure reading.
Thank you. This is what I was thinking. It’s like they have a lawn mower carburetor in there. And then they have a MP gauge that goes to 60 inches! lol. It also doesn’t reach max controlled RPM at full throttle at start of takeoff, which defeats the purpose of a variable pitch prop.
Overall disappointed with the engine modeling.
The other day, I was taxiing a bit fast, like 30 knots, I know I know, but when I tried to hold down the tail for some braking, it took off again. Not a great flight model either.
easy to see why most developers don’t engage on this forum, or any others for that matter.
Everyone who makes aircraft content for MSFS has to create workarounds and finesse their code to get anything close to published performance numbers and behaviors. Always comes down to trade-offs and adjustments they would rather not have to make.
If it was easy to do then there would be a lot more developers making this kind of content for this flight sim. The development work on this aircraft is ongoing as the MSFS updates are rolled out and THEY make improvements to engine and flight performance, fuel flow and management behaviors, as well as improvements to their information and communication regarding the SDK, so that developers can have a fighting chance to use it more effectively - rather than just fighting with it.
The GAS Stearman PT-17, 13, and A75L300 have been widely accepted as a proper addon and GAS is currently working on the Airshow or Super Stearman 450HP version. Won’t be much fun if all you do is stare at the MP gauge - but for the rest of us it should be more than fine. They will do their best to ensure it.
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i don’t understand. when there’s a problem with a plane this is one forum where people can raise those concerns. software development is an iterative process that requires feedback. are folks always chivalrous in their comments? no but unfortunately that’s life these days.
agreed, but when those workarounds break something fundamental to flying, that’s not acceptable. having accurate readings from your gauges is very important when you’re flying. one check that you would normally make in this plane prior to taking off is to confirm that you can achieve the proper manifold pressure. irl, if i couldn’t make that happen i would be taxiing back to and requesting maintenance on the plane.
bottom line, there are ways to make this work properly because i don’t own a single other plane in the sim with this “workaround”. imo, the dev should be open to hearing about this and fixing it.
edit: case in point, the very first time i flew this plane, i lined up on the runway and pushed my throttles forward. when the map didn’t increase as far as i thought it should, i stopped and started trying to figure out what the problem was. once i determined that weather wasn’t the cause of my woes, i started looking at my hardware, etc. fortunately i had a friend who also got the plane and had been on the dev’s discord and they reported that this was a “feature” that i could safely ignore.
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Yeah but… MP is an absolutely critical gauge.
Anyway, this is a case of something potentially as simple as:
Don’t:
manifold_efficiency_table = 0:0.2, 1:0.69
Do:
manifold_efficiency_table = 0:0.2, 1:0.985
and
power_scalar = 0.7
Or, any similar variety of .cfg tuning to achieve desired results without unintended side effects.
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Indeed I am the developer and after 6 months at 5 hours a day, I think I deserved a few holidays : I answer you from Quebec so currently I am not in front of my workstation and I cannot answer on these “wise advice”.
Even though I’m the developer, I’m not the director of GAS, which is manage by two men that I’m not a part of and I do not publish a fix without GAS’s explicit agreement and request.
Modifying the CFG file will undoubtedly fix the behavior of the manifold at high RPMs but by reducing the power scalar (1 to 0.7) it is the whole power curve that is modified and mainly the range between 700 and 1800 RPMs. Have you thought about it? We worked several weeks with the pilots to ensure that the aircraft’s behaviour was as representative as possible: and mainly during take-offs and landings.
A flight model is a very complicated mix between several configuration files, this one has been validated by two still active Stearman pilots and I think their opinion is probably more accurate.
FSX, P3D and MSFS are a mix of several configuration files. Changing one parameter very often affects others and sometimes not in the desired direction. Reaching a good compromise is already a satisfactory result.
Perhaps, it is possible that the two pilots who tested this flight model did not pay attention to the hight value of the manifold. It is also possible that the understanding of the gauge seemed correct to them.
Currently, I can’t do anything (I don’t have MSFS here), we’ll see with GAS staff and the Team when I return to France.
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I also have been working directly with a very experienced Stearman pilot and have easily made a new engine config for the plane that matches (or comes very close to) real world numbers. This very experienced Stearman pilot feels having full manifold pressure is indeed a requirement and thanked me for taking steps to make it closer to reality as when he confronted GAS about it, the excuse was “sim limitations”. Yes, compromises have to be made in a lot of cases for setting up an aircraft but lacking 1/3 of your apparent engine power would have me taxiing back in to the maintenance hangar, not saying “oh well - it must be ok”. Much like scoobyx above, I found myself wondering if I had a binding wrong or something set up incorrectly as this is the only plane with a deliberate (severe) MP limitation.
That being said, I do love this plane and how it flies and I’d love to see it more accurate - that’s all.
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This remark made me smile … hence the link I put above to clarify (Manifold Pressure vs. RPM: What's the Difference? - Pilot Institute). The speedometer goes up to 220 MPH but the aircraft will never reach them 
So I repeat: for the moment I can’t do anything, it will take a few days for the Team to discuss it, that we propose a fix if necessary and that it is thoroughly tested before publishing it
@Cpmoustache: I am not editing my answers for fun but I try to correct them to be as factual as possible without hurting people by my answers since English is not my native language.
We may have different opinions, but I am not here to seek quarrels or hurt the people to whom I answer: I point out that I take the time to answer despite being on vacation.
For your answer " only plane with a deliberate (severe) MP limitation." , I would like to point out that I never wrote that this was a deliberate choice on our part, as you suggest. Besides that’s why I added that we will talk about it with the Team when I come back from holidays.
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I love this plane. But having to use the camera pull down menu to start the engine, refuel, remove the chocks, etc breaks the immersion for me. Does anyone know if these commands can be mapped to a controller or keyboard? I’ve mucked around with custom camera views but can’t get them to work.
if you haven’t remapped them you can use 'left CTRL+1,2,3,4, and 5
to jump from the cockpit to the various positions outside of the aircraft.
To return to the cockpit just press the same access twice IE: Press left CTRL+3 to access the crew start then press the same key combo again to jump back into the cockpit…
Hello,
Back in France since yesterday morning, and despite my “jet flag” (6 hours), I was able to study this problem of manifold.
Reading the first versions of the project (even my engine files from August 2023) and also many feedback from testers in the last 6 months I could see that the table of parameters had been modified by me. Why I don’t remember, may be a typing error on my part, sorry.
Unfortunately our attention during the December/Junuary was too heavily monopolized by the tuning of the 3 flight models, no one in the team of testers and also myself, noticed this problem. Anyway it seems that this should be amended.
In my opinion, two options are possible after correction of “manifold_efficiency_table” :
- either modify the power_scalar but this affects the totality of the engine response curve
- either revise the “engine efficiency” parameters between 1500-2300 RPMs range to maintain current engine performance.
For now, I do not want to delay the current project, so I will see what is possible to do.
For those who would agree to an improvement of this problem, I will create a patch including some other features that I had planned for the February release but that could not be integrated for lack of time.
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Love this guy, sounds seem decent but the startup sound really bothers me. I don’t know what a real one sounds like so that is saying nil . Thanks to the team for putting it out there at a fair price. I’m loving the constant speed propeller model.
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Anyone know if this is coming to the Marketplace?
No, it is not planned.
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