Auto Information: mixed review

Intake (down), compression (up), power (down), exhaust (up). Memory aid: suck, squeeze, bang, blow. Only the power stroke pushes on the crankshaft.

Intake: only the intake valve open. Compression: both closed. Power: both closed. Exhaust: only the exhaust valve open.

$\text{cam rpm}=\frac{\text{crank rpm}}{2}$. One four-stroke cycle takes two crank revolutions (720 degrees), and each valve opens once per cycle. A 3600 rpm crank turns the cam at 1800 rpm.

$\text{power strokes/min}=\frac{\text{rpm}}{2}\times n$, with n cylinders. Each cylinder fires once every two revolutions; a 4-cylinder at 3000 rpm gives 6000.

$V=\frac{\pi }{4}{B}^{2}S$: B is bore (diameter), S is stroke, same units; cm give cc. Multiply by cylinder count for total; 1000 cc = 1 L. Doubling bore quadruples volume.

$CR=\frac{V_s+V_c}{V_c}$: swept volume plus clearance volume, over clearance volume. 450 cc swept and 50 cc clearance give 10:1. It is unitless.

Gasoline: spark ignition; a compressed air-fuel mix (about 9:1 to 12:1) is lit by a spark plug. Diesel: compression ignition; air alone is squeezed (about 15:1 to over 20:1) until hot enough to light injected fuel.

The connecting rod links piston to crankshaft; the crankshaft turns reciprocating motion into rotation; the flywheel stores rotational energy to smooth speed between power pulses (it creates no energy).

$AFR=\frac{m_{air}}{m_{fuel}}$, a mass ratio written as a number to 1. Divide, never add: 375 g air with 25 g fuel gives 15:1. Gasoline stoichiometric is about 14.7:1.

$\lambda =\frac{AF{R}_{actual}}{AF{R}_{stoich}}$, unitless. $\lambda =1$ is stoichiometric, below 1 is rich (extra fuel), above 1 is lean (extra air). 13.23/14.7 = 0.90, rich.

No. Fuel is in the denominator, so a higher AFR means less fuel per unit of air, a lean mixture. A lower number (such as 12:1 for gasoline) is rich.

Tank (stores), pump (moves and pressurizes), filter (removes debris), rail (holds pressurized fuel at the engine), injector (meters fuel by pulse width into the port or cylinder).

The coil is a transformer: when primary current is switched off, it induces tens of thousands of volts in the secondary. The spark plug delivers that voltage as a spark across its gap in the chamber.

Timing is measured in crank degrees before TDC. A larger BTDC number fires earlier (advanced); a smaller one fires later (retarded). The ECM retards timing when the knock sensor detects knock.

Closed loop: the ECM reads the upstream oxygen sensor and corrects injector pulse width continuously. Open loop: fueling from stored tables without oxygen feedback, as during cold start or wide-open throttle.

A sensor reports a condition (crank position, MAF, MAP, oxygen, knock). The ECM decides. An actuator does physical work on command (injector, ignition coil, throttle motor, fuel pump).

It is a wax-pellet valve that stays closed while the engine is cold for quick warm-up and opens near its rated temperature (often about 180 to 200 F) to send coolant to the radiator. It does not cool or pump.

Stuck closed: coolant cannot reach the radiator, so the engine overheats quickly and the upper hose stays cool. Stuck open: slow warm-up, low gauge reading, weak cabin heat and poorer fuel economy.

The spring-loaded cap holds pressure, raising the boiling point (about 3 F per psi). Opening it hot drops pressure suddenly, letting scalding coolant flash to steam and spray out.

Only at idle or in traffic suggests weak low-speed airflow, such as a fan that does not run. Only at highway speed or heavy load suggests limited capacity: clogged radiator, low coolant or weak pump flow.

Sump, pickup screen, oil pump, filter, galleries, bearings and other moving parts, then drainback to the sump. The pump makes flow; the filter only cleans.

It is a viscosity rating. The number before W (winter) rates cold-temperature flow, lower meaning better cold flow; the number after the dash rates viscosity at hot operating temperature.

No. Level is how much oil is in the sump; pressure is how hard the pump pushes oil through the passages. A full engine can still have low pressure from a clogged pickup, worn pump or worn bearings.

$Q=mc\Delta T$: Q in kJ, m in kg, c in kJ/(kg$\cdot$°C), $\Delta T$ in °C. Rate $P=Q/t$; 1 kJ/s = 1 kW. 6 kg, c = 3.6, 15°C gives 324 kJ.

$\text{ratio}=\frac{n_{in}}{n_{out}}=\frac{N_{driven}}{N_{driving}}$. A 12-tooth driving gear turning a 36-tooth driven gear is 3:1; output speed = input speed divided by the ratio.

$T_{out}=T_{in}\times \text{ratio}\times \eta$ ($\eta$ as a decimal). 150 N$\cdot$m through 2.5:1 at 90% gives 337.5 N$\cdot$m. Apply efficiency to torque or power, never to speed.

Above 1 (e.g. 3.5:1) is a reduction: slower output, more torque. Exactly 1:1 is direct drive. Below 1 (e.g. 0.7:1) is overdrive: faster output, less torque.

Multiply, never add: $R_{overall}=R_{trans}\times R_{final}$ (times any transfer-case ratio). 2.8:1 with a 3.5:1 final drive gives 9.8:1, not 6.3:1.

Placed between two gears, it makes the output turn the same direction as the input (as in reverse). Its tooth count cancels out, so it does not change the overall ratio.

$n_c=\frac{n_L+n_R}{2}$: carrier speed is the average of the axle speeds. If one wheel is held still, the other spins at twice carrier speed.

A clutch is a pedal-operated friction device (flywheel, friction disc, pressure plate) that connects or disconnects engine torque. A torque converter is a fluid coupling (impeller, turbine, stator) that slips and can multiply torque.

A synchronizer uses a friction cone to match gear and shaft speeds so a manual shift engages without grinding. A transfer case splits power to front and rear driveshafts in 4WD and may add a low range.

$P=\frac{F}{A}$. Pressure is the same everywhere in one circuit, so output force $F_2=P\times A_2$; a bigger piston gets more force. Example: 400 N on 5 cm² gives 80 N/cm², so a 20 cm² caliper piston gets 1,600 N.

$\frac{F_2}{F_1}={\left(\frac{d_2}{d_1}\right)}^2$ because area grows with diameter squared (the $\frac{\pi }{4}$ cancels). A 2 cm master and 5 cm caliper piston give 6.25 times the force.

$KE=\frac{1}{2}m{v}^2$ (m in kg, v in m/s, KE in joules). Energy goes with speed squared: double the speed means 4 times the energy and heat; 4 times the speed means 16 times.

$d=\frac{v^2}{2a}$, d in m, v in m/s, a in m/s². Tripling speed makes d nine times longer; doubling a halves it. Example: 25 m/s at 6.25 m/s² stops in 50 m.

It is where hydraulic pressure is first created: the pushrod drives one or two pistons that trap fluid and force it into the lines. Modern tandem units feed two separate circuits so one leak leaves partial braking.

Soft or spongy pedal: air, boiling fluid vapor or a leak. Very hard pedal needing big leg force: lost booster assist. Firm pedal but the car slows less after heavy use: friction fade from overheated pads and rotors.

No. ABS mainly keeps wheels rolling so the driver can steer; on gravel or deep snow a locked wheel may stop shorter. Press firmly and hold; do not pump. Pulsing in hard stops is normal ABS action.

Disc: caliper, pads, rotor. Drum: wheel cylinder, shoes pushed outward, backing plate, return springs. Shoes never press a rotor. DOT 5 is silicone and must not be mixed with glycol DOT 3, 4 or 5.1; use the fluid on the cap.

$\text{ratio}=\frac{\text{steering-wheel angle}}{\text{road-wheel angle}}$. At 15:1, turning the wheel 450° gives about $450÷15=30$°. A lower ratio (12:1) is quicker but needs more effort.

$F=kx$ and $E=\frac{1}{2}k{x}^2$; k is spring rate in N/m, x is compression in m, F in N, E in J. Convert mm to m first: 40,000 N/m times 0.018 m = 720 N. Doubling x stores 4 times the energy.

Springs support the weight and set ride height. The damper only controls how fast the spring compresses and rebounds, turning motion into heat via oil forced through valves. Repeated bouncing at normal ride height points to worn dampers.

Toe from above (front edges in = toe-in, apart = toe-out). Camber from the front (top leaning out = positive, in = negative). Caster from the side (top of steering axis tilted rearward = positive).

Positive caster helps wheels return to center and steadies straight-line travel, but too much makes steering heavy. Excess toe gives feathered wear; excess camber wears one shoulder of the tread.

No. Balancing adds small rim weights to correct uneven mass so the wheel spins smoothly; a shake in one speed band suggests imbalance. Alignment sets toe, camber and caster, affecting pull, tracking and tire wear.

A spring-steel bar linking left and right suspension. It twists when one side compresses more than the other, as in a turn, reducing body roll. It does little when both wheels rise together. End links attach it to each side.

Power steering only reduces driver effort; the car still steers mechanically, though harder, if assist fails. The sidewall number is the tire's maximum pressure; set cold pressure from the door-jamb placard or owner's manual.

$V=I\times R$: V in volts, I in amperes, R in ohms ($\Omega$). Rearranged, $I=\frac{V}{R}$ and $R=\frac{V}{I}$. Example: 12 V across an 8 $\Omega$ heater gives 1.5 A.

$P=V\times I=I^{2}R=\frac{V^2}{R}$, P in watts. A 12 V fan drawing 5 A uses 60 W; a 24 W accessory at 12 V draws $I=\frac{P}{V}=2$ A.

Series: $R_T=R_1+R_2+\dots$, one current, drops add to the source voltage, one open stops all. Parallel: each branch gets full voltage, branch currents add, $\frac{1}{R_T}=\frac{1}{R_1}+\frac{1}{R_2}$, so $R_T$ is below the smallest branch.

Runtime $t=\frac{C}{I}$ (hours, Ah, A); energy $E=V\times C$ in watt-hours. A 40 Ah battery at 2 A lasts 20 h; 12 V times 60 Ah is 720 Wh. Real usable capacity is lower.

Amp-hours (Ah): charge delivered slowly, often over a 20-hour test. Cold-cranking amps (CCA): current a new battery delivers for 30 seconds at 0 °F while staying at or above 7.2 V. Neither replaces the other.

The starter is a DC motor: battery electricity in, rotation out, only while starting. The alternator is a belt-driven generator: rotation in, electricity out (AC induced in the stator, rectified to DC by diodes) whenever the engine runs.

A fuse protects: its metal strip melts open when current exceeds its rating, guarding the wire. A relay switches: a small control current in its coil closes heavy contacts to run a big load. Never replace a fuse with a higher rating.

No. Resting voltage mostly shows state of charge, not state of health. A worn battery can read full yet collapse under cranking load; a load or conductance test judges health. Let surface charge settle before reading.

P = passenger car; 215 = section width in mm; 65 = aspect ratio (sidewall height is 65 percent of width); R = radial construction; 15 = rim diameter in inches.

$h=w\times \frac{AR}{100}$ and $D=2h+d_{\text{rim}}$, with rim inches times 25.4 mm. For 195/55R16: $h\approx 107$ mm, rim 406.4 mm, $D\approx 621$ mm.

No. The sidewall shows the maximum pressure the tire can hold. Use the vehicle maker's recommended cold pressure on the Tire and Loading Information label (driver's door jamb) or in the owner's manual.

Check cold, before driving or after sitting a few hours out of the sun. Driving warms the air and normally raises pressure a few psi; never let air out of a hot tire to match the cold figure.

The number is a load index looked up in a table (91 = 615 kg per tire). The letter is the maximum rated speed under proper conditions (H = 130 mph). Neither is a target.

Steady: at least one tire is significantly low (US rule: 25 percent or more below recommended cold pressure). Flashing about a minute then steady: a system malfunction, so low pressure may go unwarned; check tires with a gauge.

Tread worn flush with the wear bars is 2/32 inch (about 1.6 mm): replace the tire. The DOT number ends in four digits, week then year, so 1822 means week 18 of 2022.

$F=mr{\omega }^2$ (m in kg, r in m, $\omega$ in rad/s, $\omega =2\pi f$). Force grows with speed squared: doubling wheel speed gives 4 times the force, which is why a small imbalance shakes on the highway.

$\tau =rF\sin \theta$: r is distance from fastener center (m), F is force (N), $\tau$ in N·m (or lb-ft). At 90° it is just $rF$: 20 N at 0.30 m gives 6 N·m; at 30° only half as much.

$T_w=T_s\times \frac{L}{L+E}$, L = wrench length, E = crowfoot reach. For 45 N·m, L = 0.40 m, E = 0.05 m: set 40 N·m. Turning the crowfoot 90° to the handle removes the need to correct.

Six-point: grips the flats over a larger area, least likely to round a stubborn bolt. Twelve-point: grips nearer the corners but fits at twice as many positions, helpful when swing room is tight.

Drive size is the square hole for the handle (commonly 1/4, 3/8 or 1/2 inch). Opening size is the fastener it fits (for example 14 mm). The two numbers are unrelated.

Use it only to tighten to a spec, never to loosen stuck bolts. Stop at the click, pull smoothly at the grip, keep it calibrated, and store a click type at its lowest setting. Finish lug nuts with it, not an impact wrench, in a star pattern.

Feeler gauge: small gaps (valve clearance, plug gap). Micrometer: precise outside size such as rotor thickness. Dial indicator: runout, with $TIR=\text{max}-\text{min}$; +0.05 and -0.03 mm gives 0.08 mm.

Voltage: across the part, in parallel, circuit running. Current: open the circuit and put the meter in series (or use a clamp meter). Resistance: power off and part isolated; OL means open circuit.

No. A jack only lifts and can leak down or roll. Chock the wheels that stay on the ground, set rated jack stands in pairs at the support points, lower the car onto them and check it is steady before going under.

No-crank: the engine does not turn over, so check the starting circuit (battery, cables, interlocks, solenoid, starter). Crank-no-start: it cranks at normal speed but never runs, so check fuel, spark, air and engine control.

No. Lamps draw a few amps; a starter draws well over 100 A. A weak battery or corroded cable can light bulbs brightly yet collapse under starter load. Test battery voltage and connections.

$V_{\text{terminal}}=V_{\text{rest}}-I{R}_{\text{internal}}$. With 12.6 V, 150 A and 0.02 $\Omega$: drop is 3 V, so the terminals read about 9.6 V during cranking.

$V_{\text{drop}}=IR$ and $P=I^{2}R$. At 150 A through 0.004 $\Omega$: 0.6 V lost before the starter and 90 W of heat, which is why a bad terminal can feel hot.

Steady MIL: the computer saw a fault affecting emissions or engine control; have it checked soon. Flashing: severe misfire that can damage the catalytic converter. A DTC points to a circuit or area, not a specific failed part.

No. Clearing erases freeze-frame data and resets readiness monitors to incomplete, but the cause remains and the lamp may return. Record freeze-frame data before clearing; a permanent code clears only after the computer verifies the repair.

A misfire follows engine rpm and can be felt while parked or idling. A wheel or tire shake follows road speed, often in one speed band like 60 to 70 mph, and disappears when stopped.

$d\propto v^2$, and $d=\frac{v^2}{2a}$. Doubling speed from 30 to 60 mph makes braking distance 4 times longer: 45 ft becomes about 180 ft. Reaction distance adds $d=vt$ on top.