1. Sparks the air-fuel mixture
   Protects the electrical system
2. Charges the battery
   Regulates battery discharge

Like other fuses, the fuses in your car protect the different areas of the electrical system from a sudden and dangerous spike in the flow of electricity. When that happens, the fuse breaks, closing the circuit from damage.

1. It helps carbonate the gas
   It turbocharges the gas pump
2. It keeps the fuel from evaporating
   It keeps rainwater out of the body

If you've ever spilled gas and noticed it evaporated quickly, you know that keeping a cap on the tank is a good idea. If you don't, it can also cause the check engine light to come on, because the system detects a fuel leak that needs to be addressed. It's best to turn the cap until it clicks, so you know everything is sealed up tight.

1. Cuts down on exhaust noise
   Spools a turbo
2. Reduces emissions
   Releases turbo pressure

Catalytic converters, or cats as some people call them, use a catalyst to transform some of the most harmful gases in your exhaust to gases that are less harmful or not harmful at all.

1. Keep the engine aligned
   Reduce engine vibrations
2. Smooth out the ride
   Protect against spinal injuries

Because shocks compress, and they're part of the suspension system, they take the shock out of bumps, potholes, and other road imperfections. Without them, riding in a car would be far less comfortable.

1. Connects the piston to the crankshaft
   Connects the doors to the frame
2. Connects the engine to the frame
   Connects the transmission to the wheels

Connecting rods need to be extremely durable since they must deal with the extreme forces exerted by the pistons after combustion downward, which in turn push the crankshaft to rotate.

1. Fastens the wheel to the hub
   Keeps wheels balanced
2. Improves fuel economy
   Attaches the hub to the axle

The lug nuts are the giant nuts you see on your car's wheels. Like other nuts, they're fasteners that keep the wheels secured to the hubs, so they don't fly off as you're driving down the road.

1. In case you have stuff blocking the taillights
   They help other drivers tell for sure when you're slowing or stopping
2. Just in case your other lights burn out
   To help truckers spot you at night

All modern cars have a third brake light, which only illuminates when you press on the brake pedal. When your headlights are on, it can be hard for people sometimes to tell if you've pushed on the brake pedal, if they can only see the taillights. The third brake light eliminates any confusion.

1. Generates electricity
   Regulates electrical currents
2. Changes gas to horsepower
   Transfers power from one wheel to the next

An alternator is belt-driven, so it uses the power from the engine to create electricity, which it then uses to recharge the battery and power things like the headlights, radio, dash lights, etc. while you're driving. If this starts to go out, you might have trouble starting your car, or notice the lights dim momentarily as you drive.

1. Tuck the wheels in more
   Widen the wheel offset
2. Repair damaged hubs
   Make the wheels wider

Wheel spacers bolt onto the axle, just like a wheel, and have studs that you use to bolt on the wheel. They will increase the wheel offset, plus they can change the bolt pattern if you so desire.

1. Dissipate fog
   Provide better visibility in certain conditions
2. Eliminate fog in front of a car
   Boost vision of the car's roof

Fog lights have a wide and short beam pattern, plus they're mounted low on a car. That helps you see better in fog, heavy rain, snow, and similar situations. Trust me, turning on your brights has the exact opposite effect.

1. To make driving more difficult
   To smooth out acceleration
2. To connect and disconnect the engine and wheels
   To make acceleration more abrupt

The clutch literally creates or bridges the connection between the engine and transmission, which sends power to the wheels. It allows the wheels to turn at one speed, and the engine to turn at another.

1. To put an engine on the wall
   Attaches the engine to the transmission
2. Anchors the engine to the frame
   Keeps the engine on the oil pan

Engine mounts not only attach the engine to the car's frame, they're also designed to soak up some, most, or all of the engine vibrations. How exactly they do that depends on the specific mounts, which determines how comfortable of a ride you'll have.

1. Keeps the engine warm on cold days
   Powers the heater
2. Cools the air conditioning
   Warms up the gas in the winter

Most people turn on the heater in their car without a second thought. That hot air comes from the coolant flowing out of the engine, which travels to the heater core before making its way through the rest of the cooling system, so you can stay warm when it's cold outside.

1. Control transmission intervals
   Regulate air-fuel and exhaust flows
2. Control blood flow
   Regular oil flow

The valves sit in your engine's cylinder head(s) where they control when the air-fuel mixture enters the cylinders, and when the exhaust gases leave. How these work really impacts engine performance.

1. Cushion the knees from the dash
   Protect the knees from flying glass
2. Guard against broken foot bones
   Increase a car's crumple zone

Knee airbags sit in the lower portion of the dashboard, covering either the driver and/or the front passenger. In a crash, they keep the knees from hitting the dash, which is a common leg injury in car accidents.

1. Spiral intake air
   Measure air flowing into the engine
2. Measure oxygen density
   Gauge the outdoor temperature

The mass airflow sensor has one function: measure how much air is flowing into the engine. That info is sent to the ECU or management computer, which adjusts how much fuel is being injected into the engine, for an optimal mix of the two.

1. Heats up antifreeze
   Cools the coolant
2. Warms the engine
   Defrosts the oil

As the coolant flows through the engine, it picks up considerable amounts of heat, which is exactly what the coolant should do. The radiator allows air to flow through it, cooling off the coolant rapidly, so it's ready to circulate through the engine again.

1. Combustion chambers
   Intake fuel
2. The spark plugs
   Air from forced induction

An intercooler is part of a forced induction setup, usually for turbocharged cars, but sometimes for supercharger setups. The air passes through what looks like a mini radiator, cooling it further before it flows to the engine, helping to boost performance.

1. Keep brake pressure consistent
   Cool the brake system
2. Press the brake pads against the rotors
   Calibrate brake force

When you press on the brake pedal, the pressure you create in the lines causes the calipers to pinch the rotors, only it's the pads attached to the calipers that push against the rotor. Without functioning calipers, your brakes wouldn't do anything, and you'd crash.

1. Powers the pistons
   Transfers engine power to the transmission
2. Moves the engine valves
   Sends power to the wheels

In modern engines, one or more camshafts spin at the top of the cylinder head. Because they have lobes that are oblong, this motion will push the valves open for a short period, either letting the air-fuel mix into the cylinders or the exhaust gases out.

1. Controls tire temperature
   Manages engine oil viscosity
2. Regulates coolant flow
   Opens and closes the air intake

The thermostat in your car sits between the radiator and engine, controlling when the coolant flows to the radiator and doesn't. It's triggered by the temperature of the coolant, so your engine warms up quickly but doesn't overheat.

1. Measures electrical output
   Monitors the crankshaft position and rotation
2. Gauges RPMs
   Measures tire speed

This electronic component works in gasoline and diesel engines to measure how the crankshaft is moving at any given moment. That info is sent to the ECU, which can then adjust timing, fuel injection, or other factors as needed.

1. Keeps you from dozing
   Displays information on the windshield
2. Prevents you from looking down
   Tells you when you need to sleep

The head-up display on a car either projects information onto the windshield or in some designs, it's a see-through screen that extends up to the windshield area on the dash. The whole point is to give you minimal but useful info like vehicle speed, navigation directions, and critical alerts so you can read them without looking down, keeping your eyes on the road.

1. Sprays fuel into the engine
   Transports fuel to the tank
2. Protects fuel from the hot exhaust
   Delivers pressurized fuel to the injectors

The fuel rail on your car attaches to the injectors, and it keeps the fuel pressurized, so everything flows precisely. Essentially, the fuel rail is a pipe, although its design is highly specialized.

1. Selects the gears in an automatic transmission
   Helps you select the right air temperature
2. Moves gears so they're engaged or not engaged with each other
   Helps with selecting radio stations.

In a car with a manual transmission, when you move the stick, you're actually moving the shift fork at the same time. It slides gears so they're either engaged or not engaged with other gears in the transmission, changing the gear ratio.

1. Keeps the engine well-weighted
   Makes the back of a car heavier
2. Translates shifter movements to the transmission
   Offsets engine vibrations

Some engine designs aren't well-balanced, so the solution is to use a balancing shaft. The eccentric weighted shaft works to counteract engine vibrations, so you don't feel them as you drive at any speed.

1. Starts the engine
   Keeps the engine turning
2. Sparks the fuel
   Changes combustion force into a rotational movement

The crankshaft sits at the bottom of the engine, where it's connected to the pistons through the connecting rods. As the pistons move up and down, the crankshaft rotates, sending that spinning energy to the clutch and the transmission.

1. Spark fuel
   Warm diesel fuel
2. Start the engine
   Warn other drivers

Diesel fuel can gel in really cold conditions, making it impossible to start a vehicle unless you have a way to get it flowing. That's where the glow plug comes in, because it's designed to get things moving by heating up the fuel just enough.

1. Bleeds heat of the the radiator
   Soaks heat out of hoses
2. Pushes hot air out of a certain area
   Boost aerodynamics

Some cars have heat extractors on the hood or in the fenders. They're vents, but are pointed so the air flows out and toward the back of the car, instead of ramming into the vent from the front.

1. It pumps oil around the engine
   It holds the oil when it's not circulating
2. It directs oil to the wheels
   It sends oil to the transmission

The oil sump is really just a place where the engine oil collects. Sometimes called the oil pan, the sump is where the oil pump draws oil to circulate around the engine and other components.

1. Forces the car to the ground
   Turbocharges the engine
2. Cools the brakes
   Boosts aerodynamics

The rear diffuser is a specially shaped section of a car's underbody. It helps the air transition from high-velocity flow under the car to a slower movement behind it, which in turn boosts aerodynamics. That means improved handling, acceleration, and efficiency.

1. Allows fresh air to flow into the crankcase
   Forces air into the intake system
2. Allows exhaust gases out of the engine
   Helps the car run when submerged in water

The breather attaches to the PCV valve using a vacuum to draw fresh air into the crankcase and forcing gases produced by combustion out of the engine. Without this feature, certain engines would accumulate harmful chemicals and even water, which would be disastrous.

1. Relays fuel pressure info
   Keeps the pump lubricated
2. Controls electrical flow to the fuel pump
   Controls the rate of fuel flow

The fuel pump relay controls when the fuel pump draws electricity off the oil pressure sending unit, or other nearby components. If the relay starts to fail, you'll have problems starting the engine or see that the engine no longer runs as strong as before.

1. Connect the suspension to the frame
   Control the steering angle
2. Direct the steering rack
   Soak up vibrations

The control arms use bushings to connect up to the vehicle frame, and a ball joint to attach to the suspension, at least in most designs. They're designed to minimize the transfer of vibrations from the suspension to the frame, but that's not their primary purpose.

1. Keeps the belt from hanging loose
   Spools the belt up when you're done
2. Cinches up the belt in a crash
   Ensures the belt has enough tension to work

Similar to an airbag, the seat belt pretensioner detects when the car hits something, pulling the belts tight. That means you're forced to sit up straight, which reduces the risk of injury during a crash.