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Sean
Chapter 9 Carburetors and Injedtion
| Question | Answer |
|---|---|
| proper air - fuel mixture ratio | typically 15 parts air to 1 part fuel |
| carburetor venturi | increases the speed of airflow and decreases pressure |
| pressure reduction in the carburetor causes | 1. fuel to flow through the main nozzle into the airstream 2. lowers the boiling point of the fuel, causing some of the fuel to vaporize before reaches the cylinder 3. increases the speed of the airstream, atomizing the fuel leaving the main nozzle |
| three groups of carburetors | categorized based on airflow through the airhorn: 1. Natural draft 2. updraft 3.downdraft |
| carburetor float | maintains constant a fuel level in the float bowl. Its main purpose is to regulate fuel flow into the carburetor. |
| What happens if a float springs a leak or becomes saturated and sinks ? | too much gas will be provided to the engine |
| What is the purpose of a choke? | it provides a rich mixture for cold engine starting |
| What happens when the throttle valve is completely closed in a natural draft carburetor? | most fuel is provided to the engine through the primary idle orifice. |
| diaphragm carburetor | has an integral impulse fuel pump |
| vacuum carburetor | is always mounted on top of the fuel tank |
| when engine load decreases and engine speed increases | a governor will close the throttle |
| centrifugal governor adjusts engine speed based on | the movement of flyweights on the governor gear |
| vacuum governors | located between the carburetor and intake manifold |
| What happens in an EFI system? | the MAP sensor sends information and about intake airflow and load to the ECU |
| What does the IAT sensor do? | improves efficiency of a fuel injection system because it sends a signal to the ECU that allows the ECU to make adjustments to the fuel mixture based on air trmperature |
| Where is an O2 sensor used? | only in closed loop EFI systems |
| What does an O2 sensor do? | monitors the chemical composition of exhaust gases, and provides feedback to the ECU that is used to adjust fuel trim |
| Atmospheric pressure decreases | as altitude increases |
| economizer circuit | reduces pressure in the carburetor float bowl during part throttle operation |
| types of speed controls an engine can have | governor and manual |
| Updraft carburetors | DO NOT have larger passages than downdraft carburetors |
| A closed loop EFI system | makes continuous adjustments to the fuel trim based on the level of oxygen in the exhaust gases |
| Something Fuel injected small engines do not have | a gravity fed fuel system |
| fuel injection systems | are used in small engines |
| the fuel injector | is located in the throttle body |
| a carburetor | relies on pressure differences to mix fuel and air and keep the mixture moving in the right direction |
| acceleration well | a reservoir containing extra fuel that is drawn into the airstream when the throttle valve is suddenly opened |
| hunting | a governor malfunction that results in engine speed oscillations |
| choke system | restricts airflow into the carburetor to enrich the air fuel mixture |
| throttle system | regulates the amount of air fuel mixture entering the cylinder |
| air bleed | allows air to mix with fuel in a fuel circuit |
| main discharge nozzle | delivers fuel to the venturi when the engine is operating at speeds above idle |
| float system | maintains a constant fuel level within the carburetor |
| venturi | increases air velocity and reduces pressure by restricting the carburetor's air passage |
| acceleration system | provides additional fuel when airflow through the carburetor is maximized |
| economizer circuit | reduces air pressure in the float bowl when the engine is operating at part throttle |
| idling system | delivers a small amount of air fuel mixture to the cylinder when the throttle valve is closed |
Created by:
annin.e