Car spark plug: Why is this inconspicuous little part so important?

1. How does a spark plug work?

A spark plug is a precision device that integrates mechanics, electricity, and thermodynamics:

• Center electrode:Made of high-grade materials such as nickel alloy, platinum or iridium, the diameter is usually between 0.4-1.5mm. The iridium electrode can be as thin as 0.4mm, which can produce more concentrated sparks
• Ground electrode: Generally L-shaped, forming a precise discharge gap (0.6-1.2mm) with the center electrode. High-performance spark plugs use a conical or V-shaped cut design
• Insulator: Made of high-purity alumina ceramic, it is resistant to temperatures up to 1500℃ and has an insulation resistance of more than 10GΩ
• Metal shell:The shell is made of steel with a hexagonal head (usually 16mm or 21mm) for easy disassembly and assembly, and also plays a role in heat dissipation
• Internal structure: Contains a glass sealing layer and a resistor to ensure sealing and anti-interference capabilities

The ignition process of the spark plug is actually a series of complex physical phenomena:

• Voltage rise:The ignition coil increases the 12V voltage to 10,000-40,000V
• Electric field establishment: A strong electric field of 3-5kV/mm is formed in the electrode gap
• Gas breakdown: Ionization occurs when the electric field strength exceeds the air breakdown threshold
• Arc formation:The electron avalanche effect forms a plasma channel
• Energy release:30-100mJ of energy is released within 1-2ms
• Flame core formation:A high-temperature flame core with a diameter of 1-2mm is generated
• Flame propagation: The flame spreads to the combustion chamber at a speed of 10-30m/s

2. What are the specific functions of spark plugs in the engine?

• Improvement of the combustion process by spark plugs:

Ignition reliability: The misfire rate of iridium spark plugs is <0.1%, while that of ordinary spark plugs can reach 1-3%

Flame propagation speed: The thin electrode design can shorten the combustion cycle by 5-10%

Lean combustion capability: High-performance spark plugs can stably ignite at an air-fuel ratio of 18:1

Cold start performance: Sufficient ignition energy can still be provided at -30℃

• The impact of spark plug status on environmental performance:

Fuel consumption impact: Aging spark plugs can increase fuel consumption by 5-15%

Emission control: Stable ignition can reduce HC emissions by 30-50%

Catalyst protection: Reduce misfires to avoid overheating and damage to the three-way catalytic converter

Idle speed stability: A good spark plug makes the idle speed fluctuation <±10rpm

3. Installation and use specifications of spark plugs

Precautions:

Completely cool the engine (can be left to stand for more than 4 hours)

Prepare a special spark plug sleeve (with magnetic or rubber sleeve)

Check the electrode gap of the new spark plug (adjust with a feeler gauge if necessary)

Installation steps:

Apply a small amount of copper-based anti-sticking agent to the thread

Screw it in by hand to ensure that the thread is properly engaged

Tighten it to the specified torque (usually 20-30N·m) in 2-3 times

Precautions:

Avoid over-tightening that may damage the cylinder head thread

Ensure that the high-voltage wire is connected reliably

Check the engine operation after installation

4. Spark plug daily maintenance guide

Regular inspection of spark plugs is an important means to prevent engine failure. Professional inspection methods can help you accurately evaluate the working status of spark plugs, find problems in time and take corresponding measures. The appearance inspection method is a relatively basic but also very important diagnostic method. After removing the spark plug, the following parts should be observed:

Electrode status: The electrode of a normally working spark plug should be light brown or grayish white, dry and free of oil stains. If black carbon deposits are found, it indicates that the mixture is too rich or the combustion is incomplete; if there are oil stains on the electrode, it may indicate that there is organic oil infiltration in the cylinder.

Electrode wear: Check whether the center electrode and side electrodes are rounded and thin. Normal electrode edges should be sharp. Excessive wear will reduce ignition energy.

Insulator: The white ceramic part should be free of cracks or damage. Cracks may cause leakage.

Abnormal deposits: Red or white abnormal deposits may indicate excessive fuel additives or coolant infiltration into the combustion chamber.