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69 votes
Accepted

Why does the mixture knob spin?

It's called a Vernier Control. It has an internal screw that is part of the fixed housing, with threaded jaws that engage the threads around the outside and are part of the knob. When you turn the ...
  • 110k
12 votes
Accepted

Does the mixture and throttle setting affect the quality of priming of fuel prior to start?

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 ...
  • 110k
8 votes
Accepted

How does the DA 40 NG automatically control the mixture, pitch and power by just providing one throttle?

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: ...
  • 16.3k
7 votes
Accepted

What happens if you change power setting with constant mixture setting?

All things equal, the throttle setting has no meaningful impact on the stoichiometry of the fuel-air mixture, it just changes the volume of that mixture that's allowed to flow into the cylinders. ...
6 votes
Accepted

Cessna 182Q (parachute operation) - climb leaning with CHT

Don't bother will all that. Without a proper 6 channel Exhaust Gas Temperature gauge, and fuel injection, you can't hope to do any of that sort of anal-retentive leaning to the nth degree kind of ...
  • 110k
6 votes
Accepted

Do Diesel engines have a mixture option?

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 ...
  • 54.6k
5 votes

Do Diesel engines have a mixture option?

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 ...
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5 votes
Accepted

Does the DA-42 automatically lean to clean fouled spark plugs?

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 ...
5 votes
Accepted

Why does enriching the mixture ratio beyond stoichiometry give more power?

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 ...
  • 110k
5 votes

Why does enriching the mixture ratio beyond stoichiometry give more power?

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 ...
5 votes

Why does a fuel-injected engine have a mixture control?

Basically two reasons: You want to use richer mixture for climb as the engine would otherwise easily overheat during slow flight at high power without the excess fuel providing extra cooling. And ...
  • 54.6k
5 votes

Why does the mixture knob spin?

Probably because the actuation mechanism contains a screw drive which allows fine adjustment of the mixture- either that, or the screw drive locks the pull knob firmly in position so it will not ...
4 votes
Accepted

On the G1000 lean assist page, what does a positive delta EGT mean?

I believe I have found the answer to my question in the G1000 manual (previously I had looked at the POH for the C172 NavIII). The ASSIST Softkey aids in the leaning process by identifying the peak ...
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4 votes
Accepted

How do you lean mixture using only the instruments on a C172 Skyhawk?

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 ...
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4 votes

How does the DA 40 NG automatically control the mixture, pitch and power by just providing one throttle?

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, ...
4 votes
Accepted

Why is the fuel:air ratio of a turbojet engine not around ~1:15 (the stoichiometric ratio)?

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/...
  • 21.9k
4 votes

What is the relationship between fuel mixture, throttle setting and engine temperature?

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 ...
  • 96.5k
3 votes

What is the relationship between fuel mixture, throttle setting and engine temperature?

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....
  • 26.9k
2 votes

Why does enriching the mixture ratio beyond stoichiometry give more power?

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 ...
2 votes

How to lean with constant speed prop on multi-engine aircraft without EGT

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 ...
  • 110k
2 votes

Carbureted Rotax engines have no mixture control, how do they handle less dense air?

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 ...
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2 votes

Does a lean mixture result in a higher cylinder temperature for a given power setting?

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 ...
  • 110k
2 votes

How does the DA 40 NG automatically control the mixture, pitch and power by just providing one throttle?

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). ...
  • 8,690
2 votes

How does the DA 40 NG automatically control the mixture, pitch and power by just providing one throttle?

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 ...
2 votes

Why is the fuel:air ratio of a turbojet engine not around ~1:15 (the stoichiometric ratio)?

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 ...
1 vote

Why does a fuel-injected engine have a mixture control?

The throttle butterfly varies the volume of air that enters the engine, but fuel-air mixture is a function of weight of air (and fuel). The control unit doesn't sense weight of incoming air.
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1 vote

What is the air/fuel mixture ratio in a turbojet engine?

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 ...
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