Recip engine fuel metering systems

Question 1

What is a stoichiometric mixture?

Answer 1

A mixture in which all of the chemical elements are used and none are left over 15:1

Question 2

What fuel mixture would be used to produce the most power?

Answer 2

A mixture that is slightly richer than chemically perfect

Question 3

What mixture is considered to produce max power?

Answer 3

12:1

Question 4

What is vapor lock?

Answer 4

The fuel vaporizes in the lines, pumps, or other units

Question 5

How do you reduce the possibility of vapor lock?

Answer 5

Fuel lines are kept away from sources of heat
Sharp bends and steep rises are avoided
Boost pumps

Question 6

What are some contaminations found in avgas?

Answer 6

Solids
Water
Ice
Microorganisms

Question 7

What is the purpose of metering fuel?

Answer 7

To adequately mix the proper amount of fuel with the combustion air entering into an egine during all phases of engine operation

Question 8

What are the three types of fuel metering systems?

Answer 8

Float carburetors
Pressure carburetors
Fuel injection systems

Question 9

What are the different systems on a carburetor?

Answer 9

Main metering
Idling
Accelerating
Mixture control
Idle cutoff
Power enrichment

Question 10

What functions does a venturi perform in a carburetor?

Answer 10

Proportions the air-fuel mixture
Decreases the pressure at the discharge nozzle
Limits the airflow at full throttle

Question 11

What type of ice can for in carburetor?

Answer 11

Impact ice
Fuel ice
Throttle ice

Question 12

How does a pressure injection carburetor work?

Answer 12

Works on diaphragms and air pressure for fuel metering

The distance the fuel valve opens is determined by the difference between the two pressures acting on the diaphragm

Question 13

What are the advantages of fuel injection?

Answer 13

Even fuel/air mixture distribution
More power
Less fuel
Less problems with carb ice

Question 14

How does fuel injection work?

Answer 14

Deposits a continuous flow of fuel into the induction systems near the intake valve just outside of the cylinder

Question 15

What type of carb is a float carb?

Answer 15

Airflow sensing

Question 16

What does the main metering system do?

Answer 16

Supplies fuel to the engine at all speeds above idling

Question 17

What happens in the air bleed system?

Answer 17

Air bled into the main metering system decreases the fuel density and destroys surface tension

This results in better vaporization and control of fuel discharge

Question 18

How is airflow limited in a carb?

Answer 18

Throttle butterfly
Venturi size

Question 19

When does fuel not flow from the idling jet?

Answer 19

When the throttle is open

Question 20

What happens to air density as altitude increases?

Answer 20

The air becomes less dense

Question 21

What happens to the fuel mixture as altitude increases?

Answer 21

The mixture becomes richer

Question 22

How do you overcome leaning out during acceleration?

Answer 22

An accelerating pump