SGE chapter 5
An absolute ____ is any area completely free of air or atmospheric pressure
Vacuum
when closed, the choke provides a ___ air-fuel mixture needed during the starting of a cold engine
richer
Three basic functions of governors:
1. Maintain a speed selected by the operator which is within range of the governor 2.Prevent overspeeding that may cause engine damage 3. limit both high and low speeds
Three types of governors
1. air vane (pneumatic) 2. centrifugal (mechanical) 3. vacuum
gasoline must be ___ by the carburetor
vaporized
a constant speed governor should have a _____ sensitivity to function well
high
normal air-fuel mixture ration:
15 parts air to 1 part fuel
The primer on a float type carburetor pumps:
Air pressure into the float bowl forcing fuel up the nozzle
explain how a choke provides a richer air-fuel mixture
Because it leads to less air entering the combustion chamber, meaning a higher concentration of fuel is in there
a carburetor's primary function is to mix proper proportions of ___ and ___ to operate the engine
Fuel, air
Name four factors that enhance the vaporization of fuel before it enters the cylinder
Temperature Pressure TWO MORE?
Venturi principle
a restriction in a passage which causes air to move faster (increases velocity)
the ___ )) stores fuel for use during rapid acceleration
acceleration well
explain how a carburetor works
air enters the carburetor, misses with fuel in proper proportion, and the mixture flows into the combustion chamber
On an air vane governor, controlling speed is accomplished by balancing ____ pressure with ____ ____
air, spring pressure
As soon as the intake valve opens or the intake port is uncovered in a gas engine, ___ ___ forces air through the carburetor and manifold to fill that vacuum
atmospheric pressure
how is air pressure above the fuel in the float bowl and the air pressure entering the carburetor equalized
by a vent in the float bowl, which assures a continuous, free flow of fuel
the carburetor ___ is a round disc mounted on a shaft located at the intake end of the carburetor
choke
which carburetor can provide larger volumes of fuel for high speed and power requirements
downdraft
Which type of air cleaner passes the airstream through treated paper, felt, fiber, or flocked screen?
dry-type air cleaner
Diaphragm carburetors are operated by the _____ _____
flexible diaghragm
the air vane governor is operated by the stream of air created by the ____ cooling fins
flywheel
the the engine speeds up and slow down repeatedly under a constant load condition, this is known as
hunting
what is the purpose of the carburetor float
maintain a constant level of fuel in the float bowl
as fuel is used from the float bowl, and float lowers and unseats a ___ valve which lets fuel enter the bowl
needle
Three types of air cleaners widely used in small gas engines
oil bath oil-whetted dry types
which type of air cleaner element can be used again by washing it in cleaning solvent
oil-wetted air cleaner
the economizer circuit is designed to retard fuel flow to the engine at
part throttle
the percent of engine speed change required to produce a corrective movement of the fuel control mechanism is called
sensativity
if an engine is designed to run at a constant speed, the speed is adjusted with thee governor ____
spring
ability of a governor to maintain a preset speed without fluctuating is called
stability
Explain how the throttle valve controls engine speed and power
throttle valve - regulates amount of air-fuel mixture that enters the cylinder and is often linked to a governer, which is connected for a speed control. this allows for the throttle valve to open more or less mixture to maintain a given speed
explain the main purpose of the throttle valve
to regulate the amount of the air-fuel mixture entering the cylinders
T & F; air-fuel mixture requirements vary, depending upon various operating conditions
true
T& F; a Carburetor is a device that is operated by pressure differences
true
in which carburetor must air velocity be highest
updraft
in a diaphragm tpe carburetor on two cycle engines, the fuel is drawn into the crankcase during the...
upstroke of the piston
type of governor usually used on farm and industrial engines
vacuum