Second quarter exam guide

during normal engine operation, the fuel-mixture is typically a ration of ___ part(s) of air to _____ part(s) of fuel

15:1

LPG burns (faster or slower) than gasoline and has higher ignition temperatures

Slower

a(n) __________ ignition system uses electronic devices to control various ignition system functions

TCI

mufflers are often equipped with a ______ , which prevent superheated bits of carbon from exiting the engine in the exhaust.

metal screen

when closed, the choke provides the (leaner or richer) air-fuel mixture needed during the starting of a cold engine.

richer

potential energy is ____

stored energy

changing the point gap setting can also change spark _____

timing

what is the most likely reason an engine would be equipped with a fuel pump? explain.

to provide constant pressurized fuel flow to the carburetor; to ensure the engine can always provide quick acceleration and sustain power.

how well an engine breathes, or draws the air-fuel mixture into the cylinder is referred to as its ______ efficiency

volumetric

list 3 non-atmospheric conditions that can reduce horsepower...

- new engine - quality of fuel - condition of the engine

kinetic energy is ____

energy in motion

a cold spark plug installed in a cool running engine will tend to ______

foul

Pressure is_________

a force per given unit of area

most small gasoline engines run on _______ grade gasoline

regular

the acceleration ________ stores fuel for use during the rapid acceleration

well

thermal efficiency for gasoline varies from one engine to another, but is generally about

20-25%

the ignition system must be capable of producing as much as ________ volts to force the electrical current across the plug gap.

30,000

a wet bulb primer_____________ A)draws fuel from the fuel tank and pumps it directly into the engine cylinder(s) B)increases the air pressure in the float bowl to force fuel into the main nozzle C)draws fuel from the fuel tank and pumps it into the air horn D)decreases air pressure in the air horn so more fuel is drawn through the main nozzle

A)draws fuel from the fuel tank and pumps it directly into the engine cylinder(s)

In diaphragm carburetor operation, during intermediate speeds, fuel flows from the __________ A)idle discharge ports only B) idle discharge ports and main fuel discharge port C)main fuel discharge port only D)intermediate ports located on the main fuel nozzle

A)idle discharge ports only

If a smaller pulley is used to drive a larger pulley, the ________ A)torque at the driven pulley is decreased and its rotational speed is increased B)torque at the driven pulley is increased and its rotational speed is decreased C) torque and rotational speed of the driven pulley are increased D) torque and rotational speed of the driven pulley are decreased

B) torque at the driven pulley is increased and its rotational speed is decreased

in an ignition coil, the primary windings are ________ A)light gage with many turns B)heavy gage with few turns C)light gage with few turns D)heavy gage with many turns

B)heavy gage with few turns

A dry bulb primer______________ A)draws fuel from the fuel tank and pumps it directly into the engine cylinder(s) B)increases the air pressure in the float bowl to force fuel into the main nozzle C)draws fuel from the fuel tank and pumps it into the air horn D)decreases air pressure in the air horn so more fuel is drawn through the main nozzle

B)increases the air pressure in the float bowl to force fuel into the main nozzle

in order for the engine to operate, the carburetor must __________ A)compress the gasoline B)vaporize the gasoline C)condense the gasoline D)none of the above

B)vaporize the gasoline

_______ horsepower is an indication of the amount of useable power delivered at the engine crankshaft

Brake

vacuum carburetors___________ A)have both a vacuum diaphragm and a float B)are the most complex type of carburetor commonly used on small engines C) are always mounted on top of the fuel tank D)none of the above

C) are always mounted on top of the fuel tank

fuel tanks must be vented to _____ in the tank A) increase the vacuum B)prevent a vacuum C) maintain a vacuum D) none of the above

C) maintain a vacuum

the primary purpose of the ignition system of a small gasoline engine is to provide sufficient electrical voltage to discharge______ A)gasoline B)air C)a spark between the electrodes of the spark plug D)a spark to create flashover

C)a spark between the electrodes of the spark plug

a(n) _________ ignition system is a solid state system that stores its primary energy in a capacitor and uses semiconductors for timing or triggering the system.

CDI

excessive oil in a two-cycle engine fuel mixture can result in _______ A)the rapid buildup of a carbon B)incomplete combustion C)fouling of the spark plugs D) all of the above

D) all of the above

define compression ratio for an engine...

a measurement of the relationship between the total cylinder volume when the piston is at the BDC (bottom dead center) and the volume remaining at the TDC (top dead center)

if an undersized muffler installed on an engine, power will be decreased because of excessive ________

back pressure

Engine ____ is the diameter or width across the top of the cylinder

bore

dwell is the time the breaker points stay ______ during one revolution of the cam.

closed

magneto systems produce electrical current for ignition without an outside primary source of ________

electricity

spilled fuel contributes to _______ emissions

evaporative

Gasoline with a lower octane rating burns slower than gasoline with a high octane rating. True or false?

false

ribs on the ceramic spark plug insulator are there to prevent ____

flashover

a(n) ______ in the float bowl is used to equalize the air pressure above the fuel in the float bowl and the air pressure entering the carburetor.

float

a carburetors primary function is to mix proper proportions of ____ and ____ to operate the engine

fuel, and air

_____ is the most popular of all small gas engine fuels

gasoline

list 3 characteristics the ceramic spark plug insulator must have.

high mechanical strength, good heat conducting quality, and resistance to heat shock

as engine rpm increases, torque ______

increases to a point, then decreases

in figuring spark plug heat range, the length of the ______ determines how far and how well the heat travels

insulator nose

explain why gasoline should not be stored for long period of time.

it will corrode the fuel tank and increase carbon deposits

The percentage of power developed in the cylinder (indicated horsepower) compared with that which is actually delivered at the crankshaft (brake horsepower) is called _____ efficiency

mechanical

a ______________ ignition system is a flywheel magneto inductive system that employs mechanical breaker contacts to time or trigger the system

mechanical breaker point

name the three basic types of carburetors. Circle the carburetor that can provide larger volumes of fuel for high-speed and high-power output.

natural draft, UPDRAFT, downdraft

as the fuel is used from the float bowl, the float lowers and unseats a(n) ______ valve which lets fuel enter the bowl.

needle

crank ______ is the distance from the centerline of the connecting rod journal to the centerline of the crankshaft

offset

list the three types of air filters commonly used on small gas engines

oil wetted, dry, dual element

a measurement of the work an engine does and how well it does the work is referred to as engine _____________

performance

______ efficiency takes into consideration power losses caused by friction, incomplete burning of the air-fuel mixture, heat loss, and other factors

practical

the basic difference between a magneto and a battery ignition system is that the _______ current is supplies by a(n) _________ battery.

primary, lead-acid

why are flexible, weighted pick-up lines used on vehicles such as snowmobiles and ATVs? Explain

so the line will always be where the fuel is the deepest, even if the vehicle is at a steep angle

the centrifugal force at the outer edge of a flywheel applies____ stress on the material that makes up the flywheel

tensile

explain the venturi principle

the carburetor creates a partial vacuum its own by means of a venturi for the purpose of drawing fuel into the airstream

the hottest part of the spark plug is the ______ of the insulator

tip

what is the purpose of the carburetor float?

to maintain a constant level of fuel in the float bowl.

explain the purpose of a crankcase breather element

to vent crankcase pressure to prevent oil being forced out around the seals

if the temperature of the air around or inside a carburetor becomes hgh enough to vaporize the gasoline, pockets of vapor will stop all flow of fuel. This is known as______

vapor locked