Mixture and Engine Pitch..

[KnightFandragon]

What are these settings all about and how do I know what to set at what altitude and stuff? Ive been playing this game for awhile not using any of these Mixtures or Prop pitch settings, just kinda start my engine and go but am now trying to figure out what they are for. I played with prop pitch the other day in a P47 and all it did was make my engine sound weaker. Im sure it does something useful, I just dont know what it is exactly. Then I watched the Carrier take off training and saw one step was to set engine mixture to Rich mixture and was like "huh, whats that about"? Ive been flying the game with those numbers above the enemy's heads off for the last while now and it certainly makes spotting your targets harder but it actually has made my gunnery better b/c I actually focus on aiming instead of watching till the numbers get close enough then shooting haha. Then to boot im tired of being outrun by AI Normal Me109 F2 and F4 pilots while im in my Spit 25 and even my P38 while we are both in level flight and Im sure its b/c they have thier mixtures and stuff set so id like to get them figured out.

[TeeJay82]

in no expert but this is what i understand it to be.

Mixture: fuelflow to engine. also fuel cools the engine down a bit. less mixture= less performance/hotter engine and/or choke it. more mixture=cooler engine, better performance\or drown the engine. its all a matter of keeping the balance

Pitch: increases/decreases engine rpm by trimming the angle of the propellerblades. every engine has max torque/hp @ a certain rpm(performance peak). under or over rpm reduces engine power. by keeping the rpm at the given engine rpm, you allways make sure to get the most out of the engine. again also a matter of balance.

by experimenting with throttle/pitch/mix at different altitudes,speeds,dives,climbs you will soon notice what works best for the different engines. also reading up in the interweb about different plane engines will save you a great deal of time. after i started using adv.eng.controls ive increased my cruise speed in the 109s with 60/100kmh.

also if your starting with experimenting, id suggest turning engine overheat off until you feel you got the hang of it... hope this helps a bit

i cannot explain anything better in detail :P as i have no experience with this in IRL

[TeeJay82]

by sniffing around... just ignore my explination and check this one out...a bit better :P

http://12iapil2ops.0catch.com/CEM_IL2FB.pdf

[ATAG_Dutch]

What are these settings all about and how do I know what to set at what altitude and stuff?

There's a PDF file 'Aircraft Guide' in your IL2 program file which tells you recommended altitudes for supercharger and mixture settings by aircraft which is a good place to start. The higher the altitude, the less oxygen there is, so the less fuel the engine needs to mix with it. Leaving mixture on full rich will reduce the engine's burn efficiency, reducing performance.

Pitch is a bit more complex to explain, but if you fly straight and level, with your rate of climb indicator on zero, at 100% throttle you'll soon reach a steady speed. Coarsening the pitch a bit at this point is like changing up a gear in your car, your engine revs will drop but you'll accelerate if you stay on full throttle, and your revs will climb back up. If you coarsen it too much, your speed will drop as the engine tries to pull too 'high a gear'. Dropping the nose obviously increases the rate at which you speed up, and coarsening the pitch further prevents your engine over-revving.

Again similar to your car, acceleration with coarser pitch (higher gear) is less responsive, so you go to finer pitch for better acceleration, like dropping down a gear in your car. Also, finer pitch is needed for climbing, like going up a hill in your car, and to keep your engine in the optimum 'power band' of the rev range.
The AI pilots all do everything automatically in milliseconds, so their aircraft are all permanently set at optimum settings for everything.
Which is annoying.:grin:

[kendo65]

I found this guide on a website some time ago and it did a good job of explaining things to me.

(I've had to zip it as the word doc exceeded the size requirement for posting.)

Can't remember which website this came from - so apologies to the original author.

[Blackdog_kt]

Let's start simple with the mixture. In order to have a well-running engine you need a specific proportion between fuel and air. However, the higher you go, the less air there is to burn. That means we need to reduce the amount of fuel in the mixture to maintain that optimum proportion or the engine will choke due to too much fuel, hence the mixture controls.

These can be manual, fully automatic (like in the 109s and 190s) or semi-automatic (like in the USAF birds). With manual controls the pilot leans the mixture as he climbs until he perceives a slight jump in RPM (the constant speed props we'll talk about later on negate that, so it's hard to notice), the exhaust gas temperature gauge peaks or the fuel flow/power meter peaks.
However, the last couple of instruments are mostly found on civilian aircraft from the 50s onwards and not on WWII fighters. Some people say that in reality you can also tune it by ear, as the change in engine sound tone is enough to signify the optimum performance band.

In any case, peak EGT means the leanest mixture which is best for fuel economy, but runs the engine a little hotter. Leaning until peak EGT and then enriching a bit is used when cooler engine temps and a bit extra power are required, in exchange for reduced fuel economy. This is usually stated in the pilot manuals, for example "lean for cruise: peak egt..lean for power: lean until peak EGT, then enrich until 50 deg Fahreneit below peak EGT".

With semi-automatic controls the pilot's job is a lot easier. He chooses between fuel cut-off (to shut down after landing), full rich (for start-up and emergencies), auto-rich and auto-lean. Auto lean is the economy setting and auto-rich the slightly richer one used for cooler temps. In practice, planes like the P47 would cruise to the target area on auto-lean, switching to auto-rich during combat and switching back to auto-lean after combat, once engines were set again for cruise power and the engine temps dropped back into normal levels.

Finally, there are planes with fully automatic mixture systems like the 109 and 190.

Now for the prop pitch, the wall of text :-P

There's an important distinction between different aircraft in the sim and that's the propeller type.

First of all, let's start by saying that each pitch angle corresponds to a certain range of RPM depending on airspeed.

Think about cleaning your PC fans with a leaf blower: faster air means the fans also turn faster. Of course the real propellers are not driven by air alone but by the engine as well, however the effect remains.
If you were to blow air on your PC fans while they were running (which i don't recommend), you would be able to influence the RPM at which they turn despite the fact that they are driven by their own electric motor.

At some point and if you had a strong enough air current you would be able to overpower the motor and depending on the direction of the air current you generated, you could make it so that the fan runs faster or slower than the motor tries to make it run.

This is exactly what happens with aircraft propellers. If you are on a vertical dive, at some point the angle of the blades in relation to the plane of the propeller disc (aka the prop pitch) will be insufficient to resist the oncoming airflow and the propeller will speed up, transfer these rotations to the engine via the drive assembly and you will see your RPM climb. If this goes on happening theres a chance of having the engine over-rev and take damage. It's the opposite in climbs where the RPM drops.

Since this is dependent on the actual propeller pitch, in order to get around this problem designers started using propellers with adjustable pitch. This can't overcome gravity of course, but it helps keep an engine within its operating limits over a greater range of airspeeds. It makes it easier for the pilot to get the power he needs from the engine at low speeds, while also making it easier to keep the engine within operating limits at high speeds. It's easier to slow down for landing, but you are not limited that much as to what your top speed in combat will be. It's obvious this was a highly desirable effect. :-P

The most common propeller types are these:
1) Fixed pitch propeller: No pitch adjustment possible, just like the PC fans mentioned in the analogy above. The engine's RPM will drop when you climb and rise when you dive in a more marked way than in a plane with an adjustable prop pitch.
Found mostly in old military aircraft (up till the 30s or so) and in various general aviation aircraft (like Piper cubs/re-engined super cubs and some Cessnas for example). Engine controls are simpler, but you can't do some of the fancy stuff you can do with an adjustable pitch propeller.
To prevent over-revving the engine in dives you need to pull the throttle back but if it's already at idle and you're about to redline, the only thing you can do is bleed off airspeed. This makes it harder to make rapid descents than in a plane with adjustable prop pitch, as it limits the airspeed at which you can dive to keep the engine RPM within limits.

2) Variable pitch propeller: There's a lever to control prop pitch directly. This is what some (or most) of the German fighters have in IL2. Essentially, the pilot directly sets the angle at which the prop blades cut through the airflow. What this means is that this method needs constant monitoring and adjustment. The angle you set might be perfect for a certain airspeed, however the same angle might overspeed the engine if you accelerate, or it might not have enough "bite" on the air to keep your engine generating full power in a climb. A crude analogy would be to say it's like having a thousand fixed pitch props (the individual angle settings) that you can change when you need to, but you need to monitor this closely.

In fact, it was such a handful to do during combat that the luftwaffe started issuing front-line units with fully automatic systems as early as the battle of Britain. That's why 109s are so easy to over-rev in IL2 when you go from auto to manual pitch.

3) Some aircraft had an in-between solution between fixed and variable pitch props (like the SM79 and some early Hurricanes that are not modelled in IL2). They used a propeller that could be set at 2-3 standard positions but not in-between. This enabled them to switch between these settings for max power, cruise and descent, or between high and low power, but when they hit the prop's airspeed limits for the given pitch they couldn't set it to in-between positions to maintain the proper RPM, essentially facing the same problems as a fixed pitch propeller. The advantage was that the method was relatively simple and it was better than a fixed prop, as it at gave pilots a couple of extra airspeed ranges to play with.

4) Constant speed propeller: This is what most of the allied fighters have and it's overall the best for manual control. In a constant speed prop, the pitch is not controlled directly by the pilot but by a prop governor mechanism (usually inside the prop's spinner). What the pilot does by moving the lever is essentially selecting the RPM he wants to run at, from then on the governor automatically adjusts the pitch to keep that RPM.

The governor gives the selected RPM by mechanically balancing two forces: the airflow hitting the prop with the governor's "resistance" to it.
The way this happens is usually by pumping oil into the governor and i think this is what's actually controlled by the pilot's lever, the oil pressure inside the governor. The whole assembly is connected to the rods, pulleys and what-not that change the prop pitch. So, oil pressure transfers a force to the prop blades but it also works in reverse: if the airflow is fast enough the force it exerts on the prop blades transfers back to the governor. If the oil pressure in the governor is high enough to resist this the prop pitch remains the same, if not the prop pitch changes because the oil pressure is not enough to balance out the force of the oncoming airflow.

Of course limits still apply. The governor has its own gimbal limits and no matter what, in a vertical dive RPMs will increase. It's just a lot easier to manage than the previous methods and gives the pilot considerable room to play with, because for most flight regimes it does a good job of keeping the RPMs where you want it.

Generally speaking there's a correlation between RPM and manifold pressure (aka throttle settings), which prevents pilots from setting them independently from each other. If you run an engine at full throttle at low altitudes and bring the prop pitch/RPM back a lot, you risk of ruining the engine through excessive torque.

Lower RPM happens when the prop's have a high angle of attack. They "grab" more air, giving a better "pull" for the aircraft but as a result of the increased resistance the prop RPM's drop. This is efficient for cruise, where engines usually run at 55%-70% throttle. However if i were to run this RPM with the engine at full throttle, the power generated by the engine would be resisted by the prop wanting to turn slow and something would break.

Higher RPM occurs when the prop's angle of attack is low. Essentially, the prop is almost a flat disk when viewed from the cockpit. This means minimum resistance when sufficient engine power is applied. The prop can turn faster and generate quicker responses to throttle changes, just like the low gears of a car. This is why people use this setting for take-offs and landings, plus the fact that it can "carry" the power generated by an engine running at full throttle without over-torque occuring (like described above).

Let's get to the bolder part now. A lot of what happens with prop pitch changes is dependant on wether we have power applied to turn the prop. A certain pitch setting can excellent when running full throttle and disastrous when running at idle and vice versa.

For example, when sufficient power is not applied and the prop is set for high RPM, what we have is a giant windmilling airbrake. The prop blades are almost at a flat 90 degree angle to the oncoming airflow, but the engine is not giving enough power to turn them. They are still turning at a couple thousand RPMs due to the airflow however and when they do that, it's like having a solid disk of metal in your plane's nose that's slowing you down.

This can be bad if your engine quits, so always go to low RPM/high pitch when this happens to minimize resistance and maximize gliding potential in preparation for a crash landing. Better yet, feather the props if the aircraft is equipped with such a mechanism. This turns the props parallel to the oncoming airflow for the least amount of resistance.

However, it can also be good if you want to make fast descends without overspeeding your aircraft. Going to idle throttle and keeping RPM high will enable you to dive for longer periods of time without picking up excessive speed.

In reverse, if you want to catch someone diving away from in a prolonged dive, you you can lower your prop pitch/RPM to minimize resistance and pick up speed faster. In this case however you need to be mindful of much throttle you apply, in order not to suffer an over-torque. Well, at least in real life or in SoW, because over-torque is not modelled in IL2.



There's tons more we could say, but i think this is long enough as it is.

[KnightFandragon]

Holy sweet mother of info thats alot of text haha. Ill get to reading it then mess around with settings.

[Tempest123]

Let's start simple with the mixture ...

This should be a sticky

[BadAim]

This should be a sticky

Yes it should.

[KnightFandragon]

So does the Spitfire 25LB and Corsair F4uD not have mixture? and the Spit has niether? I mapped them and have had complex engine management on for forever and was just messing with those 2 and the Corsair goes from mixture 100 to mixture 120 where it starts shuddering..whats that about? The Corsair has the prop pitch....I guess ill figure it out haha

[Skoshi Tiger]

Let's start simple with the mixture. In order to have a well-running engine you need a specific proportion between fuel and air. However, the higher you go, the less air there is to burn. That means we need to reduce the amount of fuel in the mixture to maintain that optimum proportion or the engine will choke due to too much fuel, hence the mixture controls.



Just to add, a carburetor meters fuel through the volume of air that passes through it, one cubic foot of air at sea level has the same volume of air as one cubic foot of air at 20,000 feet.

Unfortuanately the fuel/air ratio is based on mass.

One cubic foot of air at sea level has a higher mass than One cubic foot of air at 20,000 feet, therefore to get the correct fuel/air ratio you need more fuel per volume at sea level than you do higher up.

Cheers!

[Azimech]

Also, there is a big difference between carburetted engines and the ones with mechanical fuel injection. All combat planes in IL2 have superchargers or turbochargers.

You will notice that some planes will start to produce black smoke and engine power drops/irregular RPM above a certain altitude. That altitude is the supercharger's critical altitude, usually around 5000 meters for most planes. This means that the supercharger cannot deliver the volume of air to the engine as requested. To keep it simple, the volume of air drops but the volume of fuel stays the same. That's why in IL2 on most planes you only need to adjust mixture above the critical altitude, although it's done in a very crude way.

Fuel injected systems like those on the FW190 and Bf109 adjust themselves automatically. And by the way the FW190 adjusts it's supercharger stage automatically as well; the Bf109 has the most elegant construction because the speed of that supercharger is adjusted the whole time by means of a engine-driven dynamic hydraulic clutch and this provides maximum boost until supercharger RPM and clutch RPM are equal. This is also less efficient than gear-driven superchargers because friction in the hydraulic clutch produces heat, and that's loss of engine power. In a car with older types of automatic transmission this loss increases fuel consumption by 20% compared with the
same car with a manual gearbox.

Turbochargers are a different story, their critical altitude (usually much higher) is the maximum allowable RPM: the higher the altitude, the more RPM the turbo has to make in order to supply the requested manifold pressure. In IL2 turbochargers are set automatically, in real life pilots had to adjust their engine RPM, manifold pressure AND turbo RPM while climbing or descending. As you climb, the pressure differential between the exhaust system and the outside air increases, which speeds up the turbo. Turbo RPM was/is regulated by a valve that controls the amount of exhaust gas that flows through the turbine.

[KnightFandragon]

And does the Jug, Corsair F4u1D, Spit 25LB, P38 L and J also auto adjust? I have my keys mapped but I cant get any of my planes to adjust thier mixtures...I even flew at 10000m and nope, it still wouldnt adjust. Prop Pitch worked on the Jug but that was it, I didnt try it on the P38 but didnt on the Corsair and Spit. THe Corsair mixture had 2 settings of 100% and 120% but the other 3 I couldnt change. Those were the only planes I was messing with but they didnt do anything, I do have complex engine management on, Ive flown with realism settings on for awhile, I just never messed around mcuh with these settings.

[Blackdog_kt]

Damn, i had a lot of typos on that long post of mine, i didn't have time to proof-read it before posting :-P

Azimech and Skoshi are also correct in their information.

As for your last question i think most of the aircraft you are testing have automatic mixture controls in IL2, that's why you can't mess with it even though you have CEM turned on and the keys mapped. The P47 in reality has the semi auto system (cut-off/full rich/auto-lean/auto-rich) but in IL2 i think it's fully auto. As for the corsair, maybe it only has auto and emergency full rich settings (the 120% setting) in IL2.

If you want to run a quick mixture test fire up the quick mission builder, select a Yak-1 with no enemies, set the starting altitude to 5000m and when you spawn set the supercharger to high gear (does the yak-1 even have one? not sure) apply full throttle and get climbing.

You'll see almost immediately that there appears to be something wrong with the engine, it sounds strange and seems to not deliver enough power. Switch to an external camera and you'll see a trail of black smoke coming out of your exhaust stacks. Now switch back to cockpit view, lower the mixture to 80% or 60% (it's done in 20% intervals per key press in IL2) and you'll hear and see (instruments) the engine come back to its senses. Switching to the external camera you can also see the black smoke trails have disappeared.

That smoke is due to the excessive fuel being burned in an inefficient manner (or being almost unburned even). There has also been talk that due to the analog nature of auto-mixture systems, it took a couple of seconds for it to stabilize if throttle was applied abruptly. This had the effect that sometimes if the pilot quickly slammed the throttles forward, a brief trail of black smoke was produced until the auto-mixture system stabilized. In turn, this was used by pilots to judge if the enemy aircraft was suddenly going to high throttle settings, a clear sign that he is aware of you and is initiating combat.

[PE_Tigar]

Just to chime in - in reality, Corsair had double the engine controls than we have at the moment in Il2. Aside from prop pitch, compressor stages, throttle, cowl flaps (that we have), it had more complicated mixture control, inter-cooler flaps, oil cooler flaps and alternate air control (not sure about the purpose of this one, some a/c have it for instruments, in case outside static gets frozen over).

As for the situation in Il2 - a/c with automatic mix perform "perfectly" - like they have a manual system that is perfectly managed. If F2 or F4 outrun you in level flight in Spit IX 25 lbs. you might be doing something wrong. Try the following - full throttle and trim the plane properly keep the slip indicator and climb speed indicator zeroed with trim and see what happens. One other thing that might be hindering you - cooler flaps on Spit IX are on closed/auto by default, so if you were running for a long time on full throttle they might be open, thus lowering your airspeed.

[TheSwede]

Dont forget to change the prop pitch as well. When you go full throtthe and have picked up speed, then lower the pitch so the blades can "dig" into the air in a more efficient way.

Just like you change gear in a car when you hit the rev limiter.

[zipper]

Wow - as a RL pilot it was fascinating reading all the advice, each post had both correct and incorrect info for the real world (not really sure about IL2 as it doesn't seem to respond as I expect it to). In RL when adjusting a constant speed (constant engine speed - rpm) prop (most allies and even the most 109s) one never thinks in terms of prop pitch but rpm. If you want to go fast or climb fast you have to have the lever full forward, 100% rpm (redline). In a dive with the prop set at 100% rpm the governor maintains redline rpm and you can have the throttle firewalled and the redline won't be exceeded until the speed gets massive as the max pitch setting will usually take some time to reach. Below about 1200/1400 rpm the governor gives up as it hits it's own limits and consequently the prop is at its default position flat against the low pitch stop. No prop lever jockeying will adjust the blades in this realm, that's why when you want to cycle the prop on a plane you have to rev the engine (it's done on runup, often right after mag check). Max performance being at 100% rpm on all aircraft (some WEP setups simply increase the rpm slightly) combat pilots (in combat) would firewall the prop and forget it, adjusting speed with throttle. If you want to use the car/gears analogy, the best I can come up with is the prop percentage would equate to the rpm range percentage the automatic transmission shifts at. 100% will shift your tranny at redline, 85% will shift it at 85% of max rpm, etc. That's the best I've got - lol. Prop blades have a rather shallow and narrow range of effective angles of attack so making a noticeably large increase will not only drop the revs a bunch but the blades lose a lot of their efficiency so the performance drops a bunch. I was in a two speed C190 once playing with this and at a slow speed with a high MAP I switched the prop to to cruise (higher pitch) and the plane actually slowed done a bit (and MAP went through the roof - yikes - always increase prop then throttle, decrease throttle then prop - but, game don't care).

Mixture, newer aircraft have better auto mixture control and that simply doesn't need to be adjusted (unless on an older plane leaving a smoke trail). Haven't found a need at all in game for the 120% mix setting. On airplanes equipped with this it substituted for water injection as the carb (actually, a pressure carb or throttle body injector) was upstream of the supercharger and was used during overboost to provide additional manifold air cooling to prevent detonation. Plug fouling could be a major problem with this setup so water injection was prefered (thats why the 190D 1944 was converted to the 190D 1945 as soon as possible).

:D

[Skoshi Tiger]

In RL when adjusting a constant speed (constant engine speed - rpm) prop (most allies and even the most 109s) one never thinks in terms of prop pitch but rpm.



Hi and welcome to the board.

In game its something you learn to live with. You disregard the RPM message on the screen when your flying a plane with a CSU, you know the prop pitch message on the screen is just showing the position of the leaver, you need to use the RPM dial to set you RPM.


If you want to go fast or climb fast you have to have the lever full forward, 100% rpm (redline). In a dive with the prop set at 100% rpm the governor maintains redline rpm and you can have the throttle firewalled and the redline won't be exceeded until the speed gets massive as the max pitch setting will usually take some time to reach.


I don't know how faithfully IL2 models WWII aircaft but the game will allow you to set an rpm higher than the red line.

Cheers!