Automotive Engineering 101: Internal Combustion Engine

Define the engine as a mechanical system that converts chemical and heat energy from fuel into mechanical energy, and classify engines by cycles, cylinder count and arrangement, and engine position.

Explore the operating cycles of internal combustion engines, detailing the four-stroke process with intake, compression, ignition, and exhaust, and compare it to the two-stroke design where these operations share strokes.

Examine cylinder arrangements across flat, inline, v-line, w-engines, and rotary engines, highlighting 180-degree flat banks, 45-degree v-angles, and space-saving designs used by Subaru and Mazda.

Explore how engine position affects performance, comparing front, rear, and mid engine layouts for advantages in cooling, space, handling, traction, and weight distribution.

The ICE uses an air–fuel combustion to convert heat into mechanical energy for rugged performance. Gasoline engines are spark-ignition, while diesel engines are compression-ignition, igniting by spark or by compression.

Explore the engine's main parts, including the block, cylinder head, camshaft, and crankshaft, and how pistons, valves, rings, and the timing chain or belt drive the cycle.

Explore the engine's working principle through a diagram of the internal combustion chamber. It highlights intake and exhaust valves, spark plug, cylinder head, engine block, and head gaskets.

Explore how a four-stroke engine operates through intake, compression, power, and exhaust strokes, with valve actions, piston movement between top and bottom dead centers, air-fuel intake, ignition, and exhaust release.

Diesel engines rely on compression ignition with no spark plug, injecting fuel at the end of compression via a diesel injector to avoid ignition as intake air reaches 0.1 bar.

Compare diesel and petrol four-stroke engines, noting diesel's higher energy density and torque. Explain petrol delivers more horsepower while diesel emits more soot and carbon monoxide and carbon dioxide.

Study the two-stroke petrol engine cycle, using ports instead of valves, with intake, compression, power, and exhaust across two strokes, and its simple, compact design versus overheating and pollution.

Explore the rotary engine, or Wankel engine, an internal combustion engine that uses a triangle rotor and apex seals to run the intake, compression, ignition, and exhaust cycle.

Explore the three valve train types for operating the intake and exhaust valves: OHV, SOHC, and DOHC, and compare their configurations in this automotive engineering overview.

Explain the overhead valve (ohv) engine mechanism with camshaft, lifter, pushrod, and rocker arm opening the valve, and note its low cost and compact durability alongside high rpm timing challenges.

Explore the single overhead camshaft design, with the cam in the cylinder head directly actuating lifters and valves to minimize vibration and allow 3–4 valves per cylinder.

The double overhead camshaft uses two camshafts for intake and exhaust with four valves per cylinder, enabling tunable timing, direct injection and improved airflow for higher power and fuel efficiency.

Explore the cooling system in automotive engines, regulating heat from combustion to maintain optimum temperature, protect engine oil, and boost performance and lifespan.

Explain how liquid cooling systems circulate coolant to remove heat from the engine, detailing components like radiator, water pump, thermostat, expansion tank, cooling jacket, and heater.

Understand how coolant blends water, antifreeze, and inhibitors to lower freezing points and raise boiling points, and avoid tap water to prevent deposits and overheating.

Explore the automotive cooling system, including the cooling jacket in the cylinder block and head, thermostats, cross-flow and traditional radiators, expansion tank, pressure cap, coolant pump, and fans.

Explore the engine lubrication system, where oil reduces friction, wear, and heat. Understand viscosity, viscosity index, viscosity rating, and boundary lubrication, including gas-tight sealing between cylinder and piston ring.

compare mineral, synthetic, and semi-synthetic engine oils and their fit for old vs modern vehicles, focusing on grades like 5w16 and 10w40.

Explain bath and splash lubrication from the bath, splash, and force feed types; show oil transfer from reservoirs to gears and rods via a splash ring, boosting efficiency without pumps.

Explore the lubrication system of internal combustion engines, including oil sump types, pumps, filters, coolers, and sensors, and how they maintain oil pressure and engine reliability.

Introduce exhaust systems and air pollution, explain carbon dioxide's warming role, and summarize air composition and pollutants like carbon monoxide and nitrogen oxides, with emphasis on environmental regulations.

Examine how additives like lead and sulfur influence combustion and exhaust; learn why lead slows combustion and prevents knocking, and why sulfur is reduced to prevent acid rain.

Learn how fuel combustion releases energy, forms carbon monoxide and unburned hydrocarbons, and how lean mixtures and exhaust gas cooling reduce nitrogen oxide emissions and boost fuel economy.

Describe WLTP, the worldwide harmonized light vehicle test procedure, replacing NEDC, to measure pollutants, carbon dioxide, and fuel and electric range under strict dynamometer and road-load conditions.

Explore how emissions are reduced through cleaner fuels, oxygen sensors, and catalytic converters. Learn about EGR, PCV ventilation, and intake air heating to boost efficiency and lower NOx.

Explore the exhaust system—from manifold and O2 sensor to ECU, catalytic converter, muffler, resonator, and heat shields—and how the three-way catalyst with platinum, palladium, and rhodium cleans gases.

Deliver petrol or diesel to the combustion chambers with timing to achieve the stoichiometric ratio lambda of one, and note petrol 14.72:1 and diesel 14.52:1 for rich or lean mixtures.

Explore the fuel tank and pump layout, including rear mounting for safety, an in-tank pump with a fuel gauge, and the fill pipe and fuel cap pathway.

Explore how steel, plastic, or flexible rubber fuel lines connect pumps to a filter, fuel rail, and metering devices, with a return line to regulate pressure by returning excess fuel.

Explore how carburetors meter fuel with fixed or variable venturi designs, using choke and throttle valves, an air filter, and atmospheric pressure effects on the air-fuel mixture and emissions.

Meter fuel via ECU signals to inject the right amount, enabling efficient combustion and emissions compliance; multi-point injection includes port and direct injection.

Explain how the fuel rail holds injectors and the pressure regulator, how the return pipe sends excess fuel back to the tank, and how pressure remains proper for the injectors.

The ECU acts as the brain of the vehicle, a microcomputer that reads sensor data, compares it to fixed maps, and controls fuel injectors.

The ECU uses data from air flow sensors to modulate fuel injection, illustrated by vane-type meters that convert flap position to voltage via a potentiometer. This vane design is obsolete due to airflow resistance and undesired performance, even with a shock absorber.

See how a hot wire air flow sensor uses a positive temperature coefficient to generate signals. Airflow cools the wire, lowers resistance, increases current; dirt buildup requires cleaning.

Explore how the throttle body regulates intake air with a pedal-controlled flap, including the idle port, and the role of throttle position sensors—switch or potentiometer—in feeding the ECU.

The map sensor, placed after the throttle body, uses a vacuum diaphragm; diaphragm resistance changes voltage per Ohm's law, providing precise ecu readings versus hot-wire or vane sensors.

See how the intake air temperature sensor signals the ECU to adjust fuel via a positive temperature coefficient resistor that may be integrated with or separated from air flow sensor.

Explore the exhaust gas oxygen (ego) sensor as a feedback device that measures air-fuel mixture quality to maintain the stoichiometric ratio, sending ecu signals of 0.8v rich or 0.2v lean.

Explore how the ignition system must ignite the air-fuel mixture at the right time, considering knock, air-fuel ratio, and engine load, and why a complete ignition system design ensures efficiency.

Explains how the ignition system converts a 12-volt battery to 8,000–20,000 volts (sometimes up to 40,000) to ignite the compressed air-fuel mixture through transformer action in primary and secondary windings.

Examine the mechanical ignition system, camshaft-driven contact breaker, condenser, and distributor routing sparks to four cylinders, and why this obsolete system lags electrical ignition in timing and emissions.

Explore distributeless electronic ignition in internal combustion engines, where a transistor replaces the circuit breaker and the ECU replaces the distributor, delivering faster response, coil-on-plug ignition, and greener emissions.

Learn how the ecu uses camshaft, crankshaft, and knocking sensor inputs along with manifold absolute pressure, coolant temperature, throttle and accelerator pedal positions, and wheel speed signals to control ignition.

Crankshaft position sensor uses a magnet and toothed gear to provide piston position reference via a missing-tooth. Camshaft sensor detects opening of valves to time ignition, enabling variable valve timing.

Describe how NOx forms when unintended self-ignition occurs in the combustion chamber, and how a NOx sensor detects the resulting vibration to signal the ECU to retard ignition timing.