Auto and Shop Information

The Four-Stroke Engine Cycle

Most car engines are four-stroke internal combustion engines. Each piston completes four strokes per cycle:

Intake stroke: Piston moves down; intake valve opens; air-fuel mixture is drawn into the cylinder.
Compression stroke: Both valves close; piston moves up and compresses the mixture, raising temperature and pressure.
Power stroke: The spark plug fires at the top of compression, igniting the mixture. The explosion pushes the piston down — this is the only stroke that produces power.
Exhaust stroke: Exhaust valve opens; piston moves up and pushes burned gases out.

The spark plug fires during the compression stroke, at top dead center (TDC).

Cylinder configurations: Inline (single row), V-type (two angled banks), Flat/Boxer (two horizontal banks), Rotary (triangular rotor).

Cooling System

Water pump: Circulates coolant through the engine and radiator. Driven by the serpentine belt.
Thermostat: Stays closed when cold (keeps coolant in the engine to warm up quickly); opens at operating temperature to allow flow to the radiator.
Radiator: Heat exchanger — transfers heat from coolant to air. Hot coolant enters at the top, exits cooled at the bottom.
Radiator cap: Pressurizes the system (~13–16 psi), which raises coolant's boiling point.
Antifreeze/Coolant: Ethylene glycol + water mix. Lowers freezing point, raises boiling point. Never use water alone in freezing temperatures — it will freeze and crack the block.
Cooling fan: Pulls air through the radiator at low speeds or when stopped.

Lubrication System

Oil reduces friction between moving metal parts and carries heat away from critical components.

Oil pump: Forces oil through passages to bearings and engine components. Driven by the crankshaft.
Oil filter: Removes metallic particles and contaminants from circulating oil.
Oil pan (sump): Reservoir that stores oil at the bottom of the engine.
Viscosity: Oil thickness rating (e.g., 5W-30). Lower numbers = thinner = better in cold. Thicker provides more protection at high heat.

Fuel System

Fuel pump: Pressurizes fuel and delivers it from the tank to the engine.
Fuel injectors: Spray a fine mist of fuel into the intake manifold or directly into the cylinder. Electronically controlled for precise mixture.
Throttle plate: Controls airflow into the engine. Pressing the accelerator opens the throttle, letting in more air, triggering more fuel injection, increasing power.
Carburetor (older vehicles): Mechanically mixes air and fuel before sending to the engine.

Electrical and Ignition System

Battery: Stores electrical energy; provides current to start the engine and power accessories when the alternator isn't running.
Alternator: Driven by the belt; generates AC, converts to DC, charges the battery and powers the car while running.
Starter motor: Electric motor that cranks the engine to start it.
Spark plugs: Create the high-voltage spark that ignites the compressed air-fuel mixture.
Ignition coil: Steps battery voltage (12V) up to the 20,000–50,000V needed to jump the spark plug gap.
Voltage regulator: Controls alternator output to prevent overcharging the battery.

Transmission System

Manual transmission: Driver selects gears using the clutch pedal and gear shifter.
Clutch: A friction disc that disconnects the engine from the transmission while shifting.
Automatic transmission: Uses a torque converter (fluid coupling) instead of a clutch; gears shift automatically.
Gear ratios: Lower gears multiply torque (more pulling power, less speed). Higher gears = more speed, less torque.
Drive shaft: Transfers power from the transmission to the axle.
Differential: Allows the driven wheels to rotate at different speeds when turning (outer wheel covers more distance than inner wheel).
4WD: Powers all four wheels for better traction on loose or slippery terrain.

Brake System

Master cylinder: Converts pedal force into hydraulic pressure in the brake lines.
Disc brakes: Caliper squeezes brake pads against a spinning rotor. Used on most front wheels.
Drum brakes: Brake shoes press outward against the inside of a drum. Often used on rear wheels.
ABS (Anti-lock Brake System): Prevents wheel lockup during hard braking by rapidly pulsing the brakes. This lets the driver maintain steering control. Without ABS, a locked wheel causes skidding and loss of steering.

Suspension System

Springs (coil or leaf): Absorb road impacts. Spring rate determines ride stiffness.
Shock absorbers/Dampers: Control spring oscillation — without them the car bounces repeatedly after every bump.
Struts: Combine a spring and shock absorber into a single unit. Common on front suspensions.
Anti-roll bar (sway bar): Torsional spring connecting left and right suspension; reduces body lean in corners.

Exhaust and Emission Control

Exhaust manifold: Collects burned gases from each cylinder.
Catalytic converter: Uses precious metal catalysts (platinum, palladium, rhodium) to convert CO and unburned hydrocarbons into CO₂ and H₂O, and reduce NOx into N₂. Requires operating temperature to function efficiently.
Muffler: Reduces exhaust noise through internal chambers.
EGR (Exhaust Gas Recirculation): Recirculates a portion of exhaust back into the intake, lowering combustion temperature and reducing NOx emissions.

Striking Tools

Claw hammer: Flat face drives nails; the claw extracts them.
Ball-peen hammer: Rounded peen used for metalwork, shaping, and setting rivets.
Mallet: Wood, rubber, or plastic head — used when you want to strike without damaging the surface.
Sledgehammer: Large, heavy hammer for demolition.

Fastening and Turning Tools

Open-end wrench: Fixed parallel jaws. Less contact area than box-end.
Box-end (ring) wrench: Fully encircles the fastener — more contact, less chance of slipping.
Adjustable (crescent) wrench: Jaw width adjusts to fit various fastener sizes.
Socket and ratchet: Interchangeable sockets; ratchet mechanism allows tightening without repositioning.
Torque wrench: Measures and limits applied torque — used when fasteners must be tightened to a specification.
Allen wrench (hex key): L-shaped hexagonal bar for socket-head screws.
Phillips screwdriver: Cross-shaped (+) tip; self-centering.
Flathead screwdriver: Single-blade tip for slotted screws.
Pipe wrench: Toothed adjustable jaws that grip round pipe; bites harder as force increases.

Cutting and Gripping Tools

Crosscut saw: Cuts across the wood grain; teeth angled to slice wood fibers.
Rip saw: Cuts along the grain; teeth act more like chisels.
Hacksaw: Fine-toothed blade for cutting metal, plastic, and pipe.
Cold chisel: Hardened steel for cutting metal or chipping concrete without heat.
Combination pliers (slip-joint): General-purpose gripping with adjustable jaw opening.
Needle-nose (long-nose) pliers: Narrow jaws for tight spaces and small parts.
Diagonal cutting pliers: Cuts wire and component leads.
Locking pliers (Vise-Grips): Can be locked onto a workpiece to hold it hands-free.
Tin snips: Cuts sheet metal.
File: Removes material by abrasion. Single-cut (fine), double-cut (faster). Shapes: flat, half-round, round, triangular.
Plane: Shaves thin amounts of wood to flatten surfaces or true edges.

Measuring and Layout Tools

Tape measure: Flexible steel tape for measuring length.
Combination square: Marks and checks 90° and 45° angles; also checks for level.
Protractor: Measures angles.
Calipers: Measures inside dimensions, outside dimensions, and depth with precision.
Micrometer: Measures very small dimensions (shaft diameters) to thousandths of an inch.
Level: Centered bubble in a liquid-filled vial indicates a level (horizontal) or plumb (vertical) surface.
Plumb bob: Weight on a string pulled by gravity to establish a perfect vertical line.
Wire gauge: Disc with notched slots to measure the diameter (thickness) of wire.

Fasteners

Nail: Driven by force; holds by friction. Common nails have thick shanks; finishing nails have small heads (hidden in wood). Sized in pennies (d) — a 10d nail is ~3 inches long.
Double-headed nail: Two heads on the shank; driven to the lower head so the upper is exposed for easy removal. Used for temporary formwork and scaffolding.
Screw: Helical threads hold by thread engagement; holds better than nails. Self-driving into material.
Bolt + nut: Passes through material; nut secures on the other side.
Washer: Flat disc under bolt head or nut; distributes clamping force, protects surface.
Lock washer: Spring or serrated washer resisting loosening from vibration.
Rivet: Permanent fastener — deformed after installation to lock it. A bucking bar backs up the rivet while the head is formed.

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