Electrical Engineering & Electronics /Chapter 7 Section B - Engine Fuel Systems
Chapter 7 Section B - Engine Fuel Systems
This deck covers key concepts and components of engine fuel systems, focusing on pressure-injected carburetors, air and fuel metering, and mixture control mechanisms.
What is the meaning of a “closed type system”?
The air and fuel within the carburator do not mix and the fuel is always under pressure. They only mix at the air discharge nozzle.
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Key Terms
Term
Definition
What is the meaning of a “closed type system”?
The air and fuel within the carburator do not mix and the fuel is always under pressure. They only mix at the air discharge nozzle.
Where is the inlet for impact air and what is it called?
It is located around the venturi and it is called the impact pressure annulus.
What is the function of the large spring in section A?
At idle speed, the spring tension opens the fuel regulator poppet valve to permit sufficient fuel pressure for operation.
Where is the inlet for the venturi suction?
The inlet for the venturi suction is located at the throat of the venturi.
What meters air flow at all settings other than full power?
Butterfly valve.
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What meters the air flow at full power?
The venturi.
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| Term | Definition |
|---|---|
What is the meaning of a “closed type system”? | The air and fuel within the carburator do not mix and the fuel is always under pressure. They only mix at the air discharge nozzle. |
Where is the inlet for impact air and what is it called? | It is located around the venturi and it is called the impact pressure annulus. |
What is the function of the large spring in section A? | At idle speed, the spring tension opens the fuel regulator poppet valve to permit sufficient fuel pressure for operation. |
Where is the inlet for the venturi suction? | The inlet for the venturi suction is located at the throat of the venturi. |
What meters air flow at all settings other than full power? | Butterfly valve. |
What meters the air flow at full power? | The venturi. |
How is idle cut-off accomplished with the pressure injected carburater? | When the mixture control is placed to the idle cutoff position, there is not enough fuel pressure to push back the discharge nozzle valve to allow fuel to exit the discharge nozzle. |
What is the function of the mixture control? | Lean mixture to compensate for decreased pressure when acending in altitude? |
What are the fuel metering forces? | Regulated and unregulated fuel that pressurizes the diagram in chamber D to close the poppet valve. |
What opens the poppet valve? | As the air metering force increases, spring tension in chamber A is overcome and the poppet valve opens, permitting pressurized fuel to enter chamber D. |
Air metering forces consists of what? | Impact pressure air in chamber A. |
The main metering system of a pressure-injection carburator consists of what 3 things? | Fuel regulator (fuel control unit), Main metering jet, Throttle Valve. |
In what setting is the manual mixture control? | Full rich. |
Where is the discharge nozzle in relationship to the butterfly valve? | The discharge nozzle is located upstream ahead of the throttle. |
What is an AMC and how does it work? | Automatic Mixture Control. A typical AMC uses brass bellows filled with helium. As ambient pressure changes, the bellows expand or contract and vary the size of the of the air bleeds in chamber A and chamber B. |
How do you get fuel for idle range? | Through the idle needle valve which is linked to the throttle shaft assembly. |
How does the mass air flow system operate? | As mass air flow increases, fuel flow volume increases. |
What fuel adjustments can be done to the carburater? | Adjust idle mixture and idle speed. |
What is the allowable coushion? | Between 1/8 and 1/4 of an inch. |
What are the two types of Acceleration Systems? | Accerleration Well, Acceleration Pump. |
Who is authorized to work on pressure-injected carburators? | Certified repaired station ONLY. |
Fuel delivered to the main discharge nozzle with a pressure-injected carburator is a function of what metered forces? | Air metered forces - used to open the poppet valve, Fuel metered forces - used to close the poppet valve. |
Name the parts for the fuel regulator in a pressure-injection carburetor. | 5 chambers, inner and outter diaphram, poppet valve assembly, main metering jet. |
As induction air enters the carburator’s (pressure-injection) body, some of it is divereted into an _______around the venturi. | Impact pressure annulus. |
The difference between the impact pressure from chamber A and venturi pressure from chamber B is called what? (Pressure-injected carburators) | Air metering force. |
What happens if air metering force increases? (Pressure-injection) | Spring tension is overcome and a poppet valve opens allowing fuel to enter chamber D. |
How does the poppet valve close? What is the name for this action? | Fuel entering into chamber D pressurizes the diaphram which causes the poppet valve to close. This action is called the fuel metering force and balances the air metering force to regulate fuel in proportion to the airflow through the venturi. |
Fuel delivered to the main discharge nozzle is a function of what? | Metered forces. |
When does the fuel become metered? | In chamber C. |
What is the difference between the manual mixture control and the AMC? | With the manual mixture control, the needle valve controls pressure differential. With the AMC, the bellows by expanding and contracting control the pressure variations. |