How a Car Works, in Detail

A car converts stored energy into motion through a coordinated set of mechanical, electrical, and software systems: the power source (engine or battery), power electronics or transmission, driveline, chassis, brakes, steering, and a network of computers and sensors that manage safety and efficiency. In combustion cars, fuel energy becomes rotational motion via controlled explosions; in electric cars, battery energy becomes torque via electric motors. Modern vehicles integrate both hardware and software to move, steer, stop, protect occupants, and communicate.

Energy and Power: The Big Picture

Every car follows the same physics: energy is stored, converted to torque, transmitted to the wheels, and managed by control systems to maintain stability and safety. The details differ between internal-combustion engine (ICE) vehicles, hybrids, and battery-electric vehicles (BEVs).

Internal-Combustion Energy Path

The following steps outline how a gasoline or diesel car converts fuel into forward motion, from tank to tires.

1. Fuel storage and delivery: A pump sends fuel from the tank through filters to injectors at controlled pressure (high-pressure for direct injection).
2. Air management: An intake system meters air; a throttle controls flow (gasoline), while turbochargers/superchargers boost pressure. Intercoolers cool compressed air.
3. Combustion cycle: Cylinders perform intake, compression, power, and exhaust strokes. Gasoline uses spark ignition near a stoichiometric air-fuel ratio; diesel uses compression ignition with lean mixtures.
4. Mechanical output: The expanding gases push pistons, turning the crankshaft to produce torque.
5. Aftertreatment: Exhaust passes through catalysts (gasoline three-way) or diesel systems (oxidation catalyst, particulate filter, and SCR with urea/DEF) to cut pollutants.
6. Driveline: A transmission selects gear ratios; a differential splits torque to wheels; axles deliver torque to tires.
7. Control: Engine and transmission control units adjust timing, injection, boost, and shifting for power, efficiency, and emissions.

In an ICE car, the key challenges are extracting useful work from heat efficiently and cleaning exhaust, both managed by precise fuel/air metering and modern catalytic systems.

Electric Vehicle Energy Path

Electric cars follow a simpler, more efficient path from battery to road, managed by power electronics and software.

1. Energy storage: A high-voltage battery pack (typically 350–400 V or 800+ V) stores energy in lithium-ion cells (e.g., NMC, NCA, or LFP chemistries).
2. Power electronics: An inverter converts DC from the pack to AC for the motor; a DC/DC converter supplies 12 V (and sometimes 48 V) systems.
3. Motor and reduction gear: One or more electric motors generate torque instantly; a fixed reduction gear delivers it to the differential or directly to the wheels.
4. Regenerative braking: Motors operate as generators during deceleration, sending energy back to the battery.
5. Thermal management: Liquid cooling/heating maintains battery and motor efficiency and longevity; many EVs use heat pumps for cabin climate.
6. Charging: An onboard charger manages AC charging; DC fast charging bypasses it to feed the pack directly via CCS or NACS connectors, depending on market and model.

EVs trade fuel systems for high-voltage safety, thermal control, and software that orchestrates power delivery and regeneration to maximize efficiency and range.

Core Systems and What They Do

Beyond the energy source, cars rely on a set of subsystems that turn torque into controlled, comfortable, and safe motion on real roads.

Engine (ICE) and Its Controls

An ICE engine uses precise airflow, fuel metering, and timing to generate torque across speeds and loads.

• Induction and charge control: Throttle body (gasoline), variable valve timing/lift, turbo/supercharging, and intercooling.
• Fuel delivery: Port or direct injection (or both), with high-pressure pumps and multi-hole injectors.
• Ignition and timing: Coils and spark plugs (gasoline), glow plugs (diesel), knock sensing, and adaptive spark timing.
• Emissions aids: EGR (exhaust gas recirculation), secondary air, and catalyst heating strategies.

These elements work under closed-loop control using oxygen sensors and other inputs to balance power, economy, and emissions in real time.

Electric Motor, Inverter, and Battery (EV)

EV propulsion packs high power density and fine torque control thanks to modern semiconductors and control algorithms.

• Motors: Permanent-magnet synchronous, induction, or switched-reluctance designs, sometimes combined for front/rear axle drive.
• Inverter: Uses IGBTs or silicon-carbide MOSFETs for efficient, high-frequency switching.
• Battery: Cell modules with a battery management system (BMS) for voltage, current, temperature, and state-of-charge/health management.
• Contactor/safety: High-voltage contactors, pyrofuses, and isolation monitoring for crash and fault protection.

Together, these components deliver rapid, precise torque with fewer moving parts than ICE systems, enabling strong acceleration and efficient energy recovery.

Transmission and Driveline

Transmissions adapt engine or motor speed to road speed, while differentials manage left/right wheel speed differences.

• ICE transmissions: Manual, automatic (planetary with torque converter), dual-clutch, or continuously variable (CVT).
• EV gearboxes: Typically single-speed reduction; some performance EVs use two-speed units.
• Differentials: Open, limited-slip, or electronically controlled clutch packs for torque vectoring.
• All-wheel drive: Mechanical (transfer case) or electric (separate axle motor) solutions.

The chosen setup influences efficiency, responsiveness, traction, and driving feel across conditions.

Braking Systems

Brakes convert kinetic energy to heat (friction) or electricity (regeneration), coordinated by control modules for stability.

• Hydraulics: Discs, calipers, pads; vacuum or electric boosters provide assist.
• ABS/ESC: Wheel-speed, yaw, and steering sensors modulate brake pressure to prevent lockup and maintain control.
• Brake-by-wire: Common in hybrids/EVs to blend regen with friction seamlessly.
• Parking brakes: Electronic actuators are now widespread.

Modern brake control balances shortest stopping distances, stability, and smooth pedal feel while maximizing energy recovery in electrified cars.

Steering and Suspension

These systems determine handling, ride comfort, and road feel while enabling driver-assistance features.

• Steering: Electric power steering (EPS) with rack-mounted motors; supports lane centering and parking assist.
• Suspension: MacPherson strut, double wishbone, or multi-link; adaptive dampers and air springs in higher-end models.
• Geometry and tires: Alignment, tire compound, and pressure strongly affect grip and efficiency.

Design choices here are a major part of a car’s personality, from comfort-oriented tuning to track-ready agility.

Electrical Architecture and Software

Vehicles are networks on wheels, with dozens of computers communicating to coordinate functions.

• Low-voltage systems: 12 V (and emerging 48 V) for accessories, lighting, and control modules.
• Buses: CAN/CAN FD, LIN, FlexRay (legacy), and Automotive Ethernet (100/1000BASE-T1) for high-bandwidth data.
• Zonal architectures: Consolidate ECUs and enable over-the-air (OTA) software updates.
• Cybersecurity: Secure boot, encryption, and intrusion detection protect vehicle networks.

This digital backbone enables features from stability control to infotainment, and allows continuous improvement via software updates.

Thermal Management

Temperature control is vital for performance, emissions, comfort, and component life.

• ICE cooling: Pumped coolant, radiators, thermostats, and oil cooling; active grille shutters reduce drag.
• EV thermal loops: Separate or shared circuits for battery, power electronics, and cabin; heat pumps improve cold-weather range.
• Exhaust heat: Used for catalyst light-off (emissions) and cabin heating (ICE).

Smart thermal strategies improve efficiency and reliability in both combustion and electric vehicles.

What Happens When You Press the Accelerator

The driver’s right pedal requests torque. How the car fulfills that request depends on its powertrain.

ICE Sequence

These are the control and mechanical steps a modern ICE car executes when you accelerate.

1. Pedal sensor reports position to the engine control unit (ECU).
2. ECU adjusts throttle (gasoline), fuel injection, ignition timing, and turbo boost.
3. Transmission selects/holds a gear for optimal torque and efficiency.
4. Crankshaft torque passes through the clutch/torque converter to the gearbox and differential.
5. Wheel torque increases; acceleration rises until load or traction limits intervene.

Throughout, sensors and the ECU stabilize combustion, shift quality, and emissions while traction and stability systems manage wheel slip.

EV Sequence

In an EV, software and power electronics translate pedal input directly into motor torque.

1. Pedal sensor reports a torque demand to the vehicle control unit (VCU).
2. Inverter modulates phase currents to deliver the requested motor torque.
3. If traction is limited, control reduces torque or vectors it between axles.
4. During lift-off or braking, regenerative torque is applied first; friction brakes add as needed.

The result is smooth, immediate response with energy recovery whenever possible, governed by traction and battery limits.

Fuel, Emissions, and Efficiency (ICE)

Modern emissions rules require tight control of pollutants while maintaining drivability and fuel economy.

Emissions Control Hardware

The following components treat exhaust or prevent pollutants at the source.

• Gasoline: Three-way catalyst and oxygen sensors manage NOx, CO, and HC; gasoline particulate filters (GPF) may be fitted on direct-injection engines.
• Diesel: Diesel oxidation catalyst (DOC), diesel particulate filter (DPF), selective catalytic reduction (SCR) with urea/DEF, and EGR.
• Onboard diagnostics (OBD-II/EOBD): Monitors systems and sets fault codes for service.

Together with precise engine calibration, these systems enable compliance across conditions, including real-driving emissions tests in many regions.

Hybrids and How They Blend Power

Hybrids combine combustion and electric drive to cut fuel use and emissions without requiring external charging (except PHEVs).

• Mild hybrid (12/48 V): Belt or crank-integrated starter-generators for stop-start, torque assist, and energy recuperation.
• Full hybrid: Electric motor can propel the vehicle at low loads; planetary gearsets blend engine and motor power.
• Plug-in hybrid (PHEV): Larger battery charges from the grid for electric-only range, then operates as a hybrid.

The control strategy decides when to use the engine or motor for best efficiency and performance given speed, load, and battery state.

Active Safety and Driver Assistance

Modern cars pair passive protections with active systems that help avoid or mitigate crashes.

• Passive: Crumple zones, high-strength structures, airbags, and active head restraints.
• Active: ABS, ESC, traction control, and brake assist stabilize the vehicle.
• ADAS: Cameras, radar, and sometimes lidar enable features like automatic emergency braking, lane keeping, blind-spot monitoring, and adaptive cruise.
• Higher automation: Limited Level 2+/3 hands-off/eyes-off features exist on select models and roads under strict conditions, subject to local regulation.

The combined effect reduces crash likelihood and severity, with software updates frequently enhancing capabilities over time.

Maintenance and Ownership Basics

Routine care keeps systems performing safely and efficiently.

• ICE: Oil and filter changes, air and cabin filters, spark plugs, coolant, brake fluid, transmission and differential service.
• EV: Fewer fluids; focus on cabin filter, brake fluid, coolant for battery/motor loops, and software updates.
• Universal: Tires, alignment, wipers, 12 V battery, and recalls/TSBs.

Following the manufacturer’s service schedule and monitoring tire pressure and software updates go a long way to reliability and safety.

What’s New and Evolving (2024–2025)

Recent advances refine how cars convert and manage energy while expanding digital capabilities.

• Higher-voltage EVs: 800 V architectures enable faster DC charging and thinner cables; silicon-carbide inverters improve efficiency.
• Charging standards: North American makers are widely adopting NACS connectors while supporting adapters for CCS; public fast-charging networks continue to expand.
• Zonal E/E architectures: Fewer, more powerful controllers centralize functions and enable robust OTA updates and features-on-demand.
• Thermal and range: Heat pumps and smarter thermal strategies reduce winter range loss in EVs.
• Driver assistance: Wider deployment of L2+ highway assist; limited L3 operation on specific roads and conditions in select markets and models.
• Batteries: LFP cells grow in popularity for cost and longevity; research and pilot programs for solid-state continue, with commercialization later in the decade.
• Regulation: Stricter CO2/efficiency targets in the U.S. and EU drive more electrification and hybridization across lineups.

These trends point to vehicles that are more electric, more software-defined, and easier to update, while improving charging convenience and efficiency.

Summary

A car works by turning stored energy into controlled torque at the wheels and managing it with mechanical systems and software for safety, comfort, and efficiency. ICE vehicles rely on combustion, gearing, and exhaust treatment; EVs use batteries, inverters, and motors with regenerative braking. Across all types, chassis, brakes, steering, thermal management, and a networked electronic architecture tie everything together—systems that are becoming more efficient, electrified, and software-driven each model year.