Power Units Test 2

SHORT ANSWER: Fuel is stored in a tank and then moves into the bowl of the carburetor. Explain how the carburetor regulates the amount of fuel in the bowl.

Has an automatic valve called needle and seat valve. Has a float.

Air moves through the carburetor fuel is pushed into the air stream through the ______________________.

Emulsion tube

Which feature described below would you likely NOT find on a two-stroke cycle engine?

Engine oil filler plug

What direction is the piston moving on the intake stroke?

From TDC to BDC

What are the 3 elements of a fire?

Fuel Air Ignition

What is the most common fuel in small engines?

Gasoline

Crankshafts are most often oriented in ___________ or _____________ directions?

Horizontal vertical

Pre-ignition occurs when the piston is moving up in the direction of what stroke?

Intake

Four strokes that occur in an engine?

Intake (suck) Compression (squeeze) Power (bang) Exhaust (blow)

The foam air cleaner element should be cleaned with ___________.

Soapy water solution

Each type of fuel has a specific point where most efficient combustion occurs. What is the ratio called?

Stoichimetric

______________ is the point at which the piston is closest to the cylinder head.

TDC (top dead center)

What is the function of a cooling fin?

The extended element of a heat-transfer device that effectively increases the surface area.

SHORT ANSWER: What is the function of a valve spring?

The opening and the closing that allows the oil to go in and out

What would be one of the possible impacts of inadequate compression?

Unburned fuel released into the exhaust

Valves move in a machined surface. What is this surface called?

Valve guide

What are the three basic elements needed to make an engine run?

air fuel ignition

Valves are typically opened by the _____________?

camshaft

What component puts gasoline into the air stream as it enters an engine?

carburetor

A(n) ________________________ is an thin cast strip designed to provide efficient air circulation and dissipation of heat away from the engine cylinder block into the air stream.

cooling fin(s)

A connecting rod establishes a connection between the _________________ and the _______________.

crankshaft piston

As compression happens in an engine the air and fuel mixture will:

heat rapidly

As cylinder bore is worn the diameter will ____________________.

increase

A Venturi in a carburetor causes the air to speed to _________________ and the air pressure to __________________.

increase increase

SHORT ANSWER: Explain why a 2 stroke engine most likely does not have an oil control ring.

it will build up so there is no need for it

Detonation is often heard as a _____________ in the engine.

knock

Octane rating provides an indication of the ability of fuel to resist what action?

knock

Which of the following additives were used in early gasoline this to increase the octane rating?

lead

One piece valve designs are often used for what type of load?

light

Undesirable and unaccounted for all that.........called _________?

maverick air

What should be used to measure the crankshaft journal wear?

micrometer

As a valve wears the valve margin will ___________________.

narrow

In a ____________ type of engine, air is drawn into the cylinder by a natural air pressure differential.

naturally aspirated

What do two stoke engines mix with gasoline?

oil

What is viscosity?

oil's resistance to flow and shear

When adjusting the air to fuel mixture to get the most power we would want to have a slightly __________ air to fuel ratio.

rich

A governor attempts to maintain a constant engine ______________________.

speed

SHORT ANSWER: What is the function of a flywheel on an engine?

spins around/rotates on crankshaft which turns parts

Cylinder wear is greatest at:

the top of the ring travel

Pistons provide a way to convert ___________________ energy into _______________ energy.

thermal mechanical

Where is the cylinder wear greatest?

top

What does BDC stand for?

Bottom dead center The furthest extent of the piston's downward (toward the crankshaft) travel is known as the bottom dead center (BDC) position

What does a gas engine produce that is toxic?

Carbon monoxide

SHORT ANSWER: Give a brief description of the function of compression rings and oil control rings.

Compression rings keep compression where it is needed to be. Oil control rings scrape all of the oil off of the cylinder wall.

SHORT ANSWER: What are the four events (strokes) that must occur in an engine? (list in order) Give a brief description of each cycle.

(suck) intake - takes it in (squeeze) compression - starts to compress (bang) power - the work being done (blow) exhaust - releases material

On a four stroke cycle engine, 2 revolutions of the crankshaft correspond to _________ revolution(s) of the camshaft.

1

Dial Calipers are measured to the nearest __________ of an inch.

.0001

SHORT ANSWER (chart question): What is the amount of taper in this cylinder at the following locations? 12:00 _______________ ----- 3:00____________________

.002 -.004

SHORT ANSWER (chart question): What is the out of round of this cylinder in the following locations? Top___________________ ----- Bottom_________________

.003 .001

In a single cylinder engine with 2 valves per cylinder, how many cam lobes would you expect to find on the camshaft?

2

A crankshaft is spinning at 1200 RPM. How fast is the camshaft spinning?

600

After a four-stroke cycle engine has completed one full operating cycle, how many degrees has the crankshaft rotated?

720

The minimum grade of gasoline recommended for small four stroke cycle engines is:

87 octane

Compression in an engine is referred to as a ratio. For a gasoline engine a compression ratio of ____:____ would be expected.

8:1

BONUS: I have a V-8 engine with a bore of 4,000 inches and a stroke of 3.48". How many cubic inches of displacement does this engine have?

???????????

The purpose of tightening head bolts in the proper sequence, and to a specific torque is to ____________________.

???????????

If a small engine is determined to be about 33 percent efficient in its use of heat produced through combustion to power the engine, where does the other 67 percent of the heat produced go?

???????????????

In the cylinder block, what holds the valve stem in alignment?

????????????????

Which of the following is a type of governor used on a small engine?

????????????????????

What is the difference between a nut driver and a screw driver?

A nut driver is a shaft and a socket. Similar to the screwdriver but used for tightening nuts and bolts

What's the difference between a ratchet and a nut driver?

A ratchet is used to tighten or loosen a bolt using a socket attachment that is interchangeable. It is a ratcheting socket wrench.

Give a description of the four strokes in an engine

Intake- During the intake stroke, the piston moves downward, drawing a fresh charge of vaporized fuel/air mixture. Compression- As the piston rises, the poppet valve is forced shut by the increased cylinder pressure. Flywheel momentum drives the piston upward, compressing the fuel/air mixture. Power-At the top of the compression stroke, the spark plug fires, igniting the compressed fuel. As the fuel burns it expands, driving the piston downward. Exhaust-At the bottom of the power stroke, the exhaust valve is opened by the cam/lifter mechanism. The upward stroke of the piston drives the exhausted fuel out of the cylinder

The strokes of a four-stroke cycle engine must happen in which of the following order?

Intake-Compression-Power-Exhaust

Valve seats and valve faces are ground on slightly different angles. What is this angle called?

Interference fit

What purpose does the engine block serve?

It contains the crankcase and all its parts, including gaskets, valves and seals. The engine block contains cylindrically bored holes for the pistons and ways to attach other components such as the cylinder head.

What is the function of a flywheel?

It is a cooling system. The shroud is shaped to direct airflow from the flywheel fan across the engine's hot spots, notably the cylinder and head. These parts have fins that aid the cooling effect by increasing the surface area available to the air.

SHORT ANSWER: Explain why a cam shaft must rotate at exactly one half of the crankshaft speed.

It is because the gear is bigger. The crank gear has to spin 2 times as fast to be able to keep up.

What does the crankshaft do? ( In terms of motion)

It is the system that converts linear energy into rotational energy

On the compression stroke of an engine the gasoline changes from a ____________ to a _____________.

Liquid Vapor

SHORT ANSWER: Explain the difference in pneumatic and mechanical governor systems.

Mechanical - is actually mechanically done Pneumatic - automatically done

SHORT ANSWER: Is this cylinder usable based on the measurements and the given reject sizes?

No

What do four stroke engines mix with gasoline?

Nothing

What are two types of air cleaners that can be used in small engines?

Oil bath Paper Foam

What is PPE?

Personal Protective Equipment

Pistons have grooves in them that hold piston rings. What is the top and bottom of each groove called?

Ring land

Which of the following oils has the highest viscosity?

SAE 10W-30

List the different types of PPE and give a reason as to why we use those certain things.

Safety glasses: to protect eyes from chemicals and etc. Long Pants: to protect your legs from sparks or spilled liquids. Closed toed shoes: to protect your toes if something falls on your foot. Hearing protection: To not damage our hearing when working with loud machines. Gloves: For when using chemicals so they do not get on our skin.