Internal Combustion Engine

Interactive Cross-Section Animation

INTAKE EXHAUST SPARK PLUG CR: 10:1 CRANKSHAFT
Cycle Progress: 0°
INTAKE
COMPRESS
POWER
EXHAUST
Speed: 1.0x
Current Stroke
Intake Stroke
0° - 180° Crankshaft Rotation
Piston moves downward. Intake valve opens. Fresh fuel-air mixture drawn into cylinder.
Component States
Intake Valve OPEN
Exhaust Valve CLOSED
Engine Parameters
Engine Type Spark Ignition
Compression Ratio 10.0:1
Ignition Method Spark Plug
Fuel Injection During Intake
Approximate Conditions
Pressure 1.0 bar
Temperature 25°C

Key Differences: SI vs CI Engines

Spark Ignition (SI)
Uses spark plug for ignition
Fuel mixed with air during intake
Lower compression ratio (8:1 to 12:1)
Ignition timing controlled externally
Throttle controls power output
Runs on gasoline, CNG, or alcohol
Compression Ignition (CI)
No spark plug - auto-ignition from heat
Fuel injected near end of compression
Higher compression ratio (14:1 to 25:1)
Ignition occurs spontaneously
Fuel quantity controls power output
Runs on diesel fuel