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25

Simple Answer: Running the engine lean or rich at different altitudes. Longer Answer: There are a couple of reasons you want to adjust the mixture of a aircraft engine. Since air density changes with altitude, it's a good idea to be able to change the fuel/air mixture at different altitudes. If you did not adjust the mixture at high altitudes you may ...


16

According to this owners manual 4.5 High altitude compensator (H.A.C. kit) H.A.C. is a high altitude compensator developed by ROTAX which adjusts the air/ fuel mixture automatically from sea level to 6500 m altitude using a special BING carburetor. This page has information on how the Bing carburetor works (with pictures!): Here's how it works Did you ...


14

The simple answer to this, is that Rotax employs Constant Depression carburetors, which is a type of Variable-Venturi carburetor. In essence the fuel/air ratio is adjusted automatically based on air pressure. The fuel jet opening is varied by a tapered needles that slides inside the fuel jet and is controlled by a vacuum operated piston.


12

On a carbureted engine, the mixture and throttle setting does not affect prime, which uses a separate injection system that draws fuel into a syringe and injects it into the intake passages at the cylinders when you push in the primer's syringe plunger. On a fuel injected engine, where the Bendix mechanical fuel injection system is pretty common, if the ...


9

The mixture control allows you to increase (to run "richer") or decrease (to run "leaner") the amount of fuel in the fuel-air mixture. As a general rule, you want to "lean out" the engine at higher altitudes because the air is thinner, and it takes more air (by volume) to burn the same amount of fuel. Mixture controls are used with many piston engines. ...


8

According to Diamonds website the NG engine is a: Austro Engine AE 300 turbocharged common-rail injected 2.0 liter diesel engine with 168 hp and EECU single lever control system The prop is a: 3 blade MT hydraulic constant speed propeller features advanced blade geometry for efficient performance, low vibration and noise. It is automatically ...


6

For fuel, any fuel, to burn, it must be mixed with suitable amount of air. Neither too little nor too much would burn. Spark-ignition engines pre-mix the fuel with air, so they must do so in the right ratio, hence the need for mixture control (which might be automated, but it must be there). However, compression-ignition (Diesel) engines are different. They ...


5

The stoichiometric mixture is the ideal chemical ratio of air:fuel, that will burn all the fuel in the mixture with no excess oxygen left. It is located at somewhere around 15 parts air and 1 part fuel per unit of mass. Mind you: the ideal ratio is based on mass, not on volume so if air density changes (as you climb/descend), as the carburetor is basically ...


5

In a gas engine, the fuel is mixed with air, usually in a carburetor, before entering the cylinders, but there is no such pre-mixing at all in the diesel, where a metered amount of fuel is injected directly into the combustion chamber, in the midst of very hot, highly compressed air. Thus, the diesel does always work with an excess of air.


5

It's because, although the Best Power mixture dumps more fuel than can be consumed by the available oxygen, the extra fuel increases the combustion speed in the charge, increasing the buildup up of pressure in the combustion chamber, and this increases the total potential energy in the air/fuel charge that can be converted to work, even though not all of ...


5

in practical terms, running rich means that despite the unevenness of the fuel-air mix both in a single cylinder firing and across all cylinders firing and across all firings in the engine, all cylinders are guaranteed to NOT be running lean on ANY firing, which means all of them will be pulling best power on EVERY firing. In addition, there is an effect ...


4

The procedure varies depending on the engine instruments in the panel. Here’s an good explanation using the EGT probe on a Cessna 172. And here are the manual pages from a Cessna 172SP that explains it. [


4

Depends on the variant. Most DA-42s are powered by turbocharged Diesel engines and do not have spark plugs. And yes the DA-42 uses an automatic run up cycle in order to test the Engine Control Units (ECU). The test button is depressed and held while the automatic ECU cycle runs on both ECUs for each engine; the pilot simply monitors the engine gauges for ...


4

Edit: to honor my original answer, I shall keep it as it is. The question was edited so much I think it would have constituted a whole new question. In it's original form, the Q presented jet engine f/a ratio as 1/4 - 1/3 and compared it to the stoich ratio of 1/15. Your numbers seem way off, except for the stoichiometric fuel/air ratio (for kerosene). ...


4

This image from Lycomings leaning instructions is likely what you are looking for: The misnomer may be that leaning always increases the temperature of the engine. If you start at full rich or something above peak lean temp, leaning the engine will cause the CHT and EGT to rise until it hits its peak. If you continue to lean beyond this the temperature will ...


3

I don’t have the graph you are looking for, but we can reason this out. If the mixture were 100% fuel and 0% air, it would be impossible for ignition to occur, so the temperature would be at a minimum. This explains what happens when you “flood” an engine by over-priming. If the mixture were 100% air and 0% fuel, there is nothing to ignite. This is what ...


2

Some new Rotax engines, such as the 912 iS, are fuel-injected and include a Full Authority Digital Engine Control (FADEC): FADEC works by receiving multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, engine pressures, and many other parameters. The inputs are received by the ...


2

This is simply due to the difference between theory and practice. It turns out that even in a well-balanced charge of fuel and air, there are highly localized “pockets” of varying mixtures at the local, molecular level. By “local level” you should think of a bunch of little fuel molecules huddling together over here and over there in different places inside ...


2

There is a big difference between "by feel" leaning of a carburated vs fuel injected engine. Carburated engines have less even fuel distribution and when leaning, one cylinder, the already leanest one, will start to misfire quite a bit before the others. So with a carb it's easy to detect one cylinder starting to misfire (the cylinder usually doesn't ...


2

Aside from the fact that the engine is computer controlled... the reason you don't have mixture control is Diesels don't use that. Gas engines need to breathe a stochiometric mix of air and fuel, i.e. proportioned correctly so there's just enough fuel for the oxygen admitted. Too fuel-lean and it won't burn. Power is controlled by partially blocking ...


2

As stated above in the last answer, it’s turbodiesel powered. Like the DA-42 and DA-62, the engine is basically power by wire, using a primary and secondary Engine Control Unit (ECU) computers, each with a dedicated battery backup, both for engine control and control over the constant speed propeller.


2

We have to remember air is only 20% oxygen. When you write the stoichimetric formula for the chemical reaction (using oxygen) on a molar basis, you get the combustion ratio by converting the fuel and oxidizer from moles to mass. To get the combustion ratio using air, you divide the oxygen mass by its fractional proportion in air. Interestingly, the ...


2

To oversimplify, you could say it's because when you are rich of peak you are getting temperature reduction from too much fuel. When lean of peak you are getting temperature reduction from too much air. Watch this guy's youtube video seminars. They are a treasure.


1

Other answers concentrated more on the 'mixture' and FADEC side of things. I'll show what it does with the prop speed. This is actually simpler and is explained right in the flight manual (p. 7-25). The prop speed is pre-programmed to follow the engine lever: So, it only uses highest RPM at takeoff power, and then reduces it at cruise settings. At very low ...


1

This cannot be answered specifically, the stoichiometric fuel/air ratio (FAR) is based on burning all oxygen, while for cooling purposes the airflow is generally much higher; therefore the FAR will be lower than the stoichiometric FAR. Note that you do not want to burn fuel at stoichiometric conditions as this produces the most nitrogen oxides. Fuel is being ...


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