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Huxley_S
06-01-2004, 08:10 PM
I'm understanding prop pitch pretty well these days but can someone explain what the mixture control does please. Is the default 100%? What happens when you change it?

Also, superchargers... what happens when you manually change this? Is it only for flying at very high altitude?

Thanks,
Hux.

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Huxley_S
06-01-2004, 08:10 PM
I'm understanding prop pitch pretty well these days but can someone explain what the mixture control does please. Is the default 100%? What happens when you change it?

Also, superchargers... what happens when you manually change this? Is it only for flying at very high altitude?

Thanks,
Hux.

http://www.baseclass.modulweb.dk/69giap/fileadmin/Image_Archive/badges/69giap_badge_huxli.jpg (http://www.baseclass.modulweb.dk/69giap)

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Covino
06-01-2004, 09:15 PM
The mixture control is used to adjust the fuel-to-air mixture for the altitude being flown. It allows the pilot to adjust the fuel-to-air ratio entering the engine. As altitude is gained, the air taken in by the engine becomes less dense. Therefore less fuel must be fed through the carburetor to so that the fuel-to-air mixture remains in the correct proportion. Lowering the mixture ratio is called "leaning the mixture" and the opposite is called "enriching the mixture." A rich mixture can result in a waste of fuel and malfunctioning spark plugs and a lean mixture can result in lower engine power or the engine cutting out due to lack of fuel.

A supercharger is basically an air pump that supplies extra air to the cylinders. This helps when the air becomes thin (at high altitude). In one of your IL-2 FB CD's you'll find a manual listing the supercharger switch altitude for many of the planes. They're mostly at 2000-3000m. If you're not sure when to switch to the second-stage just switch back and forth between the stages and watch your RPM's and see which way is more efficient.

heywooood
06-01-2004, 09:20 PM
mixture - refers the the percentage of fuel to air going into the engine - "full rich" vs "lean" - select full rich for starting the engine.. lean it out slightly as the engine reaches operating temp.. leaner still in flight - the engine should sound right. coughing an sputtering=too rich - straining and less than full output=too lean.

Superchargers ram more air into the intake - this is for higher altitudes where the air is thinner.. stage one for alts from 10 - 20 thousand feet and stage two for alts above 20 thou.

TgD Thunderbolt56
06-01-2004, 09:22 PM
EvilBen is spot on in his mechanical description. To apply this to FB, I use these simple criteria:

3000m - Go to 80% mix and supercharger stage 2
4000m - go to 60% mix and stay in stage 2 super
>4000m - check your exhaust and lean more if necessary and leave the supercharger in stage 2 above 3k.

Just make sure you change it back as you descend.

TB



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Jumoschwanz
06-01-2004, 11:14 PM
Piston engines have to have a certain ratio of air to fuel to run correctly. If the air fuel mix is too "lean" meaning too little fuel to air, then the engine will run hot and will detonate or ping. This will ruin the engine left unchecked.

When an engine runs "rich" or with too much fuel for the air it takes in, it will run cooler, but will also lose power because the excess fuel will drowned the flame front in the combustion chamber. Running rich is characterized by a "blubbering" engine, loss of power, and especially black smoke coming out of the exhaust. This excess fuel can also dilute the engine oil, wash the lube off the cylinder walls and accelerate engine wear.

As altitude increases the air thins out so on engines with no automatic compensation, one has to give the engine less fuel, 80%,60%, or whatever, to match the availiable air.

So when you are way up there and you notice the engine note is off and a loss of power, try leaning it out step by step until it runs "clean". The black smoke you are trailing running rich can be more easily spotted by hostile aircraft.

Many aircraft had an exhaust manifold temperature guage that indicated when the mixture to the engines was whithin the proper range for economical and reliable running.

S! Jumoschwanz

Tully__
06-02-2004, 01:44 AM
For a well researched & written explanation of mixture issues, you might like to read this article (http://www.avweb.com/news/columns/182084-1.html) on the AvWeb site. It is written in a technical format but intended for the non-mechanic.

In the right hand column of that article are links to a number of other articles on engine management, including a series called "Those Fire Breathing Turbos" that gives a lot of good information about operation of turbo and super charged aero engines.

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IL2-chuter
06-02-2004, 01:59 AM
The pressure carbs on US aircraft were automatically altitude adjusting, so in the realm of FB dogfights adjustment isn't necessary. Just leave it in the AUTO RICH position and GO.

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x6BL_Brando
06-02-2004, 02:15 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR> Just make sure you change it back as you descend.

TB
<HR></BLOCKQUOTE>

This is worth writing on the back of your hand!!! Taking the I-16 as an example, supercharger second stage comes in @ 2200m. So you find yourself attacked at 2500 and a turnfight develops - keep a wary eye on that altimeter! If you get down below 2000 while still in stage two you will find your plane getting slower & slower. Not good.

Another point to note is that an overrich mixture at high alt will cause your engine to leave a trail of smoke, just like hanging out a sign saying "I'm over here!"

I really enjoy the CEM 'features' - you just have to be sharp to avoid the consequences of getting it wrong.

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JJaguar
06-02-2004, 12:27 PM
I don't think mixture is modeled correctly, though I've only had the game for a month so it's possible I'm doing something wrong. I've read some tips online for complex engine management and it seems that mixture is a bit of a mystery to the general IL-2 community as well. I've read the avweb articles, but they are intended for real, experienced pilots and are too much complex information for flight sims (and frankly, they are probably way over the heads of your average gamer). You can probably find more useful, easier to read information at the Lycoming publications site (http://www.lycoming.textron.com/main.jsp?bodyPage=/support/publications/keyReprints/index.html), especially under the "Operation" section.

Here's a brief explanation of how you should set mixture. In real life, you would use the exhaust gas temperature gauge (EGT) to judge your mixture. As you lean the engine, the EGT will rise to a peak, then fall off. You get this peak because when the engine is rich of peak (higher mixture setting), you have excess fuel moving through the cylinders which cools the engine. Lean of peak, you have excess air. At peak EGT, you have a complete utilization of all available fuel and air in the cylinder. This is the theoretically optimum mixture setting.

Generally (this may vary for particular engines, of course), you would lean the mixture to this peak, then enrichen it so your EGT is ~50 degrees (Fahrenheit) cooler. There are several reasons you want to run a little rich. One, the engines tend to run a little smoother because of slight variations in fuel/air distribution from one cylinder to the next. Second, it provides a little insurance against detonation. Detonation is basically an uncontrolled explosion of the fuel/air mixture that can damage engines in pretty short order if it's severe enough. Engines are usually only susceptible to detonation at high power settings (and in fact engine manufacturers usually only allow leaning to peak EGT below certain throttle settings for this reason). Third, while peak EGT provides the best fuel economy, the peak power setting is richer (usually ~100 degrees rich of peak) and the 50 degree setting provides a good compromise between power and economy.

In IL-2, it seems that mixture has no effect at all on EGT and engine temperatures in general, and I don't think detonation is modeled. I still do strive to operate the aircraft as realistically as possible, however. I lean by listening to the engine. In cruise flight, I lean it until it starts to sound rough, then enrichen a notch until it's smooth again. In combat, I'll run it at 100% except at very high altitudes. For takeoff and landing, I'll set mixture to full rich, 120%. The real reason you want full rich on takeoff isn't power, it's to prevent detonation (remember, high power settings can cause it), and also to provide additional cooling because aircraft engines have difficulty cooling with a combination of low airspeeds and high power settings (which is exactly what you've got at takeoff). You want full rich for landing so you can be ready for a go-around at a moments notice if necessary. I actually have a short mental checklist I go through for takeoffs and landings if anyone's interested.

CraytonRoberts
06-02-2004, 05:47 PM
Yes, indeed, Jet Jag. I'd like your mental check list and I'm sure others would, too.It'd be nice to glue it to a small card. You can post it here, or email me at monumentbob@pcisys.net

[This message was edited by Tully__ on Fri June 04 2004 at 04:02 AM.]

xrvjorn
06-09-2004, 10:49 AM
Jumoschwanz wrote: "Many aircraft had an exhaust manifold temperature guage that indicated when the mixture to the engines was whithin the proper range for economical and reliable running."

Just discussed this with an IRL pilot, so I wonder: do the FB2 aircraft have this gauge?

cul8r
/J├┬Ârn

JJaguar
06-09-2004, 11:35 AM
<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Just discussed this with an IRL pilot, so I wonder: do the FB2 aircraft have this gauge?<HR></BLOCKQUOTE>

Yes they do have EGT gauges, but mixture has no effect on exhaust temperature in the game so this gauge is not useful for leaning mixture.

Heavy_Weather
06-09-2004, 11:53 AM
for a good example, start up a QMB using the I-185 at 5000m. the mission will automatically start out with the engine smoking, you'll then have to thin out the mixture.

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