ASVAB Auto Information (Engine)

Chasis

A vehicle’s skeleton. Keeps all its systems and components together. Accommodates the frame, gearbox, engines, anxles, and every other system

Frame

The main structure of the chassis, like the backbone. Supports the vehicle’s body and all its mechanical components as well as the weight of passengers and cargo inside. Also deals with torsional and vertical twisting caused by driving over uneven surfaces, torque from the engine & transmission, and tensile forces from starting, accelerating, & stopping.

Unibody Construction

The chassis and frame are integrated into one part.

Internal Combustion Engine

Engine that burns fuel mixtures to expand quickly and cause explosions. The energy from these explosions is transferred through several mechanical systems to make the vehicle move.

Engine Block

The main structural component that houses the cylinders, pistons, and other components. It is typically made of cast iron or aluminum and is responsible for supporting the engine's weight and providing a rigid mounting point for the various engine components. The engine block contains passages for coolant, oil, and other fluids and is designed to withstand the high pressures and temperatures of the combustion process.

Four-Stroke Cycle

A type of engine cycle that includes four distinct phases: intake, compression, power, and exhaust. This cycle is commonly used in internal combustion engines.

Piston

a short, solid cylinder that moves up and down or back and forth inside a hollow tube called a cylinder to change pressure, move liquids, or turn heat energy into motion. Hot burning gas from fuel pushes the piston down inside of internal combustion engines.

Intake Stroke

The engine part that opens to let fresh air or an air-fuel mix into the cylinder is called the intake valve. It opens as the connecting rod pulls the piston down from its TDC position, creating a vacuum that sucks the air-fuel mix into the cylinder. Once the piston is in the BDC, the intake valve closes, scaling the air-fuel mixture inside the combustion chamber portion of the cylinder

Compression Stroke

The connecting rode pushes the piston up, compressing the air-fuel mixture inside the combustion chamber, exciting the molecules and generating heat. The flywheel helps compress the volume of compressed air-fuel mixture trapped inside the combustion chamber

Combustion Stroke

The mixture ignites through a chemical reaction when the piston is almost back at TDC and a spark plug releases a spark. This combustion causes an explosion of energy. This explosion of energy pushes the piston which is connected to the connecting rod down, turning the crankshaft which then turns the flywheel, keeping the engine going.E

Exhaust Stroke

The exhaust valve opens as the connecting rod moves the piston back up, pushing out the leftover gases from the explosion

Camshaft

The mechanical part in charge of controlling the opening and closing of the engine’s valves. Uses pushrods at timed intervals to ensure the valves aren’t open at the same time, keeping the process running smoothly. Once the exhaust is completely expusled the engine is prepared to repeat the intake stroke.

Timing Belt/Chain

A component that synchronizes the rotation of the crankshaft and camshaft and ensures that the valves open and close at the correct time.

Piston rings

Piston rings seal the piston to the cylinder in order to prevent gases from leaking out. Similarly, oil rings stop engine oil from getting into the combustion chamber

Cylinders

House the piston and other components. Where the piston and the air-fuel mixture work together to transfer energy. Most car engines have 4,6, or 8 of these Motorcycles usually have 1-6 cylinders. The more of these that a vehicle has the more fuel that can be combusted which means more movement to the crankshaft and more power to the vehicle. Fewer of these means more efficiency but less power. Can be arranged in-line, V-type, or horizontally opposed.

Cylinder head

The part of the cylinder located above the piston. Where you find the combustion chamber as well as the intake and exhausat valves and parts.

Combustion chamber

Inside the cylinder head, right above the piston. The air-fuel mixtures combust inside this hcamberInt

Intake Valves

Let the air-fuel mixture enter the combustion chamber and seals once the mixture is inside

Exhaust Valves

Lets waste gases exit the combustion chamber.

Crankshaft

Turn’s a piston’s up and down motion into a rotary (circular motion). The crankshaft must rotate twice for a full four-stroke cycle to complete. When the tachometer (measures rpm) on a dashboard shows 4,800 rpm that means that the crankshaft is rotating 4,800 times every minute. (2400 cycles)

Wrist Pins

Connects the piston to the connecting rod

Connecting rod

Connects each piston and wrist pin assembly to the crankshaft

Fuel Injectors

Injects liquid fuel directly into the engine’s air stream (usually with an external pump). Most cars now utilize an Electronic Fuel Injection System which receives commands from the powertrain control module computer. The PCM receives info from sensors in the fuel, air, and exhaust system, and from that info it determines how much fuel the engine needs to operate at optimum levels.

Carburetors

Mixes air and fuel mechanically. As air moves quicky through the carburetor, it makes a vacuum, which draw more and more fuel into the mixture.

Throttles

Mechanically connected to the carburetor or electronically connected to the Electronic Fuel Injector computer. Advancing/Opening the throttle causes more fuel to be transferred to the carburetor or the fuel injectors. The gas pedal is connected to the throttle; the harder you press on the gas pedal the more the throttle is opened, transporting higher amounts of fuel to the carburetor or fuel injectors

Diesel Engines

Also called compression-ignition engines. Don’t use spark plugs to heat air-fuel mixtures. Instead, they use glow plugs to heat up air and compress air so tightly that fuel ignites without a spark. They are also internal combustion engines but are simpler than standard gasoline engines. This engine powers many military vehicles. More powerful and more efficient with their fuel than gasoline-powered engines. (More power at lower RPMS) They are more efficient at heavy-duty work like towing.

Octane Ratings

Measure gasoline’s ability to resist engine knocking that results from premature ignition of the compressed air-fuel mixture in one or more cylinders. Most gas stations have 3 grades: Regular, Midgrade, and Premium. By law, these ratings are shown on gasoline pumps. Correlates to how much the gasoline can be COMPRESSED before it ignites spontaneously. When an engine spontaneously combusts instead of combusting due to a spark, the engine can start knocking which can damage it over time. Using a higher rating doesn’t mean better. Only use higher rated gas if engine knocks with recommended gas.

Electric Vehicles

Have one or more electric motors that take power from a large and very heavy battery. Some of these have a smaller electric motor at each wheel so they don’t a transmission, drive shift, and axles. On-board computers control the amount of electricity sent to each motor for precise performance. Electric motors allow instant torque at their wheels and can reach high speeds very quickly.

Hybrid Vehicles

Designed for efficiency. Use gasoline or diel fuel to help power electric motors. A small engine powers the vehicle and a generator which provides electricity to the vehicle’s electric motions. They can store energy in a small battery bank that allows it to run solely on electricity for some time. Sometimes used in military applications.

Electrical Systems

A car needs a supply of electricity. Earlier models utilized automotive electrical systems that operated on 6 volts. After WWII, they became more prevalent in automobiles and 12 volts became the standard.

Car Battery

Powers an electrical motor that starts the engine is running.

Ignition Systems

Supply a high-voltage current to the spark plugs that ignite the fuel mixture in cylinders. The system takes the 12-volt current from the battery, steps it up about 20,000 volts, and then sends the current to the spark plugs. Cars with diesel engines and older cars with gasoline engines utilize coils to increase voltage like this system. Modern, solid-state electronics controlled by a computer have replaced older ignition systems. A computer controls the ignition system and adjusts it to provide maximum efficiency in a variety of driving conditions.

Coils

Use electromagnetic induction to step up the voltage. The amplified current then passes through an electrical/mechanical switching device called the distributor.

Distributor

Has a rotating shaft and switch within it called a breaker point to route the amplified current from the coils through wires to the spark plugs. Also control the timing of the spark plug discharges.

Condenser

Absorbs excess current and protects the breaker points from damage caused by the high-voltage surge.

Cooling System

The set of parts and fluids that keep your engine at the right temperature so it runs efficiently and doesn’t overheat. Without this, the engine would melt. Most internal combustion engines are liquid-cooled.

Coolant

Also known as antifreeze, it is a fluid that regulates engine temperature by absorbing heat from the engine and transferring it to the radiator, preventing overheating and freezing. Water in the system is usually mixed with coolant, which raises the boiling point of the water, keeping it from boiling away, and lowers its freezing point, keeping it from freezing in cold weather.

Waterpump

Pushes liquid coolant through waterjackets.

Waterjacket

It is a network of hollow channels or passages built directly into an engine block and cylinder head. It surrounds the hot cylinders and combustion chambers to circulate liquid coolant

Radiator

Absorbs excess heat from coolant and releases it through the fins into the air.

Lubrication System

The set of parts and processes that keep an engine’s moving parts protected by circulating clean engine oil. Its main job is to reduce friction, rpevent wear, and keep engine components cool so the engine runs smoothly and lasts longer.

Motor oil

Mixed with additives, can snatch up contaminants and drop them off in the oil filter. Makes the engine run more quietly. The pump circulates this through the engine and flows through the crankshaft and connecting rods, lubricating them. Also transfers heat elswhere as it passes through hot engine parts. Also acts as a sealer between things like the piston rings and cylinder walls.

Oil Pump

Pushes motor oil through the engine. Usually, the camshaft controls the oil pump.

Oil galleries

The pathways that oil takes through the engine

Oil pan

The reservoir where all the oil is stored. (Located at the bottom of the engine)

Pickup tube

Sends oil into the oil pump

Screen

Filters out solid materials that could clog up the system

Oil filter

Cleans out contaminants before the oil get circulated back through the engine

Exhaust System

Manages where the byproducts of combustion and other engine functions go. Exhaust gathers in the exhaust manifold then goes through steel pipes that lead to the catalytic converter. Chemical reactions that neutralize the toxic fumes occur and then they go to the muffler and out the tailpipe.

Exhaust Manifold

Connects to the exhaust ports on the cylinder head and collects the toxic gases into it, safely directing the emissions downstream toward the catalytic converter and tailpipe.

Catalytic Converter

Has a honeycomb-like set of passageways or small ceramic beads coated with catalysts that cause chemical reactions. These chemical reactions oxidize hydrocarbons and carbon monoxide into water vapor and carbon dioxide to reduce pollution.

Muffler

A place that gases can quietly expand in, reducing loud noises and managing exhaust flow

Tailpipe

Where car exhaust comes out of.

Emission-control Systems

Placed on cars by manufacturers to prevent/reduce pollution. The exhaust from vehicles cause pollutants like carbon monoxide.The combustion process causes the pollution.

Positive-Crankcase Ventilation

An old method that forces unspent or partially spent fuel back into cylinders to be used

Air-Injection Systems

Force air into the engine’s exhaust system reuse unburned or partially burned fuel before it comes out the exhaust pipe.

Exhaust-Gas-Recirculation System

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