ASVAB Auto and Shop information

Mixture of Gas and Air

(the fuel mixture)

What does the Internal Combustion engine burn?

1. Intake

2. Compression

3. Power

4. Exhaust

What are the 4 strokes that make up a cycle?

(in car engine)

Intake

This valve opens as the connecting rod pulls the piston down, drawing the gas/air mix into the cylinder

Compression

The valves are closed. The connecting rod pushes the piston up, compressing gas/air mix

Power

The spar plug ignites the gas/air mix, forcing the piston down. That pushes down on the connecting rod, turning the crankshaft; the crankshaft turns the flywheel, which keeps the engine going

Exhaust

The ___ valve opens as the connecting rod moves the piston back up, pushing out the exploded gases. The valves are times, of course, using pus rods attached to the camshaft.

Inline

The name for cylinders that are arranged in one row

V

The name for cylinders that are arranged in two rows

Four-stroke, one-cycle engine

Most people refer to engines as four-cycle engines but this is false; what are they really called?

Tachometer

Instrument in a vehicle the measures revolutions per minute; rpm

(e.g. when this displays 4,800 rpm, that means the engine is performing 4,800 cycles every minute)

Fuel must be properly mixed with air and transported within the cylinder at the proper time

What must happen in order for the cycle to happen at all?

Carburetors

___ are used (pre 1990) to mix the fuel and air mechanically. As air moves quickly through this, it creates a vacuum, which draws more and more fuel into the mixture

Fuel Injectors

___ have replaced carburetors on newer cars to perform the air/fuel mixture function.

Fuel Injector

The ___ acts as the fuel-dispensing nozzle. It injects liquid fuel directly in to the engine's air stream.

(In almost all cases it requires an external pump)

Electronic Fuel Injection computer

EFI computer stands for ___?

Determines the amount of fuel entering the engine: receives information from the sensors in the fuel, air, and exhaust system, and from that information, it determines how much fuel the engine needs to operate at optimum levels

What does the EFI computer do?

Throttle

___ is mechanically connected to the carburetor

OR

___ is electronically connected to the EFI computer

Advancing (opening) the throttle causes more fuel to be transferred to the carburetor or the fuel injectors. The accelerator (gas pedal) is connected to the throttle by mechanical linkages. The harder you push on the gas pedal, the farther the throttle is advanced (opened). Thus, more fuel is transported to the carburetor or fuel injectors.

What does a Throttle do?

Cooling system

What does the engine have because of the high temperature at which fuel burns?

Water Jackets

Water Pump

Radiator

What are the 3 components of the engine's cooling system?

Water jackets

These surround the parts of the engine that reach the highest temperatures

(engine cooling system)

Water Pump

This circulates water through the water jackets

(engine cooling system)

Radiator

(engine cooling system)

While the water circulates, it absorbs heat from the engine and then passes through the ___, where outside air cools the water.

Antifreeze

___ (a coolant) raises the boiling point of water (which keeps water from boiling away) and lowers its freezing point (which keeps the system from freezing up during cold weather)

Antifreeze

___ is usually mixed with the water in an engine cooling system

Oil Pump

A ___ circulates oil through the engine; oil flows through the crankshaft and connecting rods, lubricating it as it goes.

Friction & Heat

Lubrication (from the oil pump) reduces ___, which in turn reduces ___.

Starter

An electric motor powered by the battery that starts the engine when you turn the key

Alternator

This sends an electric current back to the battery to keep the battery charged and also powers the other electronic gadgets on your car when the engine is running

Ignition system

This supplies a high-voltage current to the spark plugs to ignite the fuel mixture in the cylinders

Ignition system

The ___ system takes the 12-volt current from the battery, steps it up to about 20,000 volts, and then sends the current to the spark plugs

Coil

In older cars, this device uses electromagnetic induction to step up the voltage

(ignition system)

Distributer

After leaving the coil, the current then passes through ___, an electrical/mechanical switching device; controls the timing of the spark-plug discharges

(ignition system, older cars)

Breaker points

A rotating shaft and a switch within the distributer that routes the current through wires to the spark plugs

(ignition system, older cars)

Condenser

This absorbs excess current and protects the breaker points from the damage by the high-voltage surge

Solid-state electronics controlled by a computer

In modern ignition systems, the distributer, coil, breaker points, and condenser have been replaced by what?

Computer

A ___ controls the ignition system and adjusts it to provide maximum efficiency in a variety of driving conditions

Drive System

Transfers the power of the engine to the wheels, making them move

Axle

The shaft on which the wheels revolve

Universal Joint

Allows the axle to move up and down without breaking the drive shaft

Drive Shaft

The connecting component that carries torque and transmits rotation

Gears

These are located on the axle and allow the vehicle to make turns

Axle shafts

These turn the wheels

Rear-wheel drive

Front-wheel drive

All-wheel drive (four-wheel drive)

What are the 3 ways wheels turn on vehicles

Rear-wheel drive

The rear wheels push the car. The drive shaft extends from the transmission to the rear axle.

Front-wheel drive

The front wheels pull the car. The drive shaft extends from the transmission to the front axle.

All-wheel drive (four-wheel drive)

All wheels push and pull the car at the same time. The drive shaft extends from the transmission to both axles.

Transmission

Rear

The ___ changes the speed of the engine in relation to the speed of the ___ wheels in rear-wheel drive.

Transmission

Front

The ___ changes the speed of the engine in relation to the speed of the ___ wheels in front-wheel drive.

Transmission

All

The ___ changes the speed of the engine in relation to the speed of ___ the wheels in all-wheel drive.

Automatic

Manual (stick shift)

2 types of transmission

Transmission

Consists of gears in several combinations so that the amount of torque used can vary according to the needs

Torque

The force that produces rotation (of wheels)

More

When the terrain is difficult (as in snow), the wheels need ___ torque in order to move.

Torque Converter

In an automatic transmission, this automatically varies the amount of torque supplied

Clutch

Found in manual transmission, this disconnects the engine from the drive shaft in order to change to a different gear (torque).

Also allows the engine to run when the car isn't moving

Brake

Device found on each wheel that applies friction to the wheel to stop its rotation

Master cylinder

Brake lines

Brake pedal

Drum brakes &/or Disc brakes

Components of a Brake system

Brake lines

Run from the master cylinder, these are filled with brake fluid

Brake pedal

This applies pressure to the master cylinder, which sends pressure (and brake fluid) through the break lines.

Drum Brakes

In this type of brake, the lines are connected to a hydraulic cylinder on each wheel. This cylinder contains pistons that move outward and force 2 brake shoes against the metal drum that rotates the wheel.

Disc Brakes

In this brake system, the master cylinder forces a caliper, containing a piston, with brake shoes on each side, to squeeze against a rotating disc in each wheel, thus stopping the car by using fluid and releasing hot air.

True

True or False

Most modern cars use both drum brakes and disc brakes

Drum Brakes

Brakes usually installed on the rear wheels.

Consists of a rotating drum with shoes that expand to rub the inside of a drum

Disc Brakes

Brakes usually installed on the front wheels.

Uses pads that pinch a rotating disc

Emissions-control systems

System placed on cars to prevent pollutants (partially combusted fuel/unburned fuel) from poisoning the atmosphere

Positive-crankcase ventilation

Air-injection system

Catalytic converter

Exhaust-gas-recirculation system

Components of Emission-control systems

Positive-crankcase ventilation

An old method (still in use) that forces unburned or partially burned fuel back into the cylinder so the fuel can be burned

Air-injection system

System that forces air into the engine's exhaust system to burn unburned or partially burned fuel before the fuel comes out the exhaust pipe

Catalytic converter

Oxidizes hydrocarbons and carbon monoxide into water vapor and carbon dioxide; this system doesn't control other types of pollutants such as nitrogen oxides

Exhaust-gas-recirculation system

Helps control nitrogen-oxide emissions by forcing some of the gases back into the cylinders

Striking Tools

Tools that apply driving force to an object

Hammer

Mallet

Sledge

3 Striking tools

Hammer

A striking tool that consists of a handle, a head, a face (part of tool that touches the nail or fastener), a claw (to pull nails), and a wedge that attaches the head to the handle.

Mallet

A striking tool that is used to strike another tool or to strike a surface without damaging it.

Sledge

A striking tool that is used to drive bolts and chisels and to break rock.

Fastening Tools

These tools apply fasteners (e.g. screws) to objects

Stapler

Wrenches

Screwdrivers

Pliers

4 Fastening tools

Stapler

A fastening tool that uses staples as fasteners.

Wrenches

A fastening tool that turns nuts and bolts. The bolt fits between the jaws of this tool and the tool turns the bolt.

(some have adjustable jaws; can also be used to keep nuts and bolts stationary)

Open-end wrenches

Box wrenches

Socket wrenches

Torque wrenches

Pipe wrenches

5 types of Wrenches

Open-end wrenches

These wrenches have open jaws

Box wrenches

These wrenches are closed.

(Some have open-end jaws on one end but this type of wrench on the other)

Socket wrenches

These wrenches have box-type sockets of varying sizes that can be attached to a handle, which in turn can be attached to an extension.

Socket wrenches

Box wrenches

Open-end wrenches

3 types of wrenches that come in set, standard sizes (either in inches or in mm); they are not interchangeable

Torque wrenches

These wrenches apply additional leverage to a fastener. These wrenches look like a socket wrench but have additional internal mechanisms designed to measure and limit the amount of torque (force) being applied.

Pipe wrenches

These wrenches have serrated jaws and grip round objects.

Screwdrivers

A fastening tool that turns screws

Standard screwdriver

Phillips screwdriver

Allen wrench

Offset screwdriver

4 types of Screwdrivers

Standard screwdriver

A screwdriver that has a flat blade at one end of the shank (the other end of the shank goes into the handle).

Phillips screwdriver

A screwdriver that has a blade shaped like a cross; this blade fits into a cross-shaped Phillips screw head

Allen wrench

A screwdriver that fits hexagonal screw heads.

Offset screwdriver

A screwdriver that has the shank set at an angle to the blade to allow the tool to be used in cramped spaces; these can have a standard blade, phillips blade, or any number of other blades

Pliers

A fastening tool that can be used to fasten and unfasten fasteners, hold objects, and cut material.

When the handles are squeezed the jaws of this tool come together

Long-nose or needle-nose

Curved-nose

Slip-joint

Wrench or vise-grip

Cutting

5 types of Pliers

Long-nose or needle-nose

These pliers have tapered jaws that can hold small objects or fit into small spaces

Curved-nose pliers

These pliers have curved jaws

Slip-joint pliers

These pliers can be adjusted so the handles lock in a certain position

Wrench or vise-grip pliers

These pliers have serrated jaws that clamp onto and hold objects of all shapes

Cutting pliers

These pliers are used to cut wire