1. Regarding policies and regulations, it can be said with certainty that upgrading spark plugs carries no regulatory risks. Spark plugs are entirely wearable automotive consumable parts. As long as the replacement and upgrade comply with the standards and specifications of your vehicle, it is entirely reasonable and legal.

2. Understanding the genuine need for spark plug replacement and upgrades. Spark plugs are wearable automotive consumable parts. For our vehicles, especially those with direct injection, spark plug wear is several times higher than normal. Therefore, for most German cars, spark plugs need to be replaced every 20,000 to 30,000 kilometers. This is a hard requirement—once the mileage is reached, spark plugs naturally need to be replaced. Additionally, for modified cars, where parameters such as horsepower and torque have been upgraded from the factory settings, corresponding adjustments and upgrades to the spark plugs are necessary. Thus, for modified cars, upgrading spark plugs is actually a very essential core requirement.

3. Briefly understand and grasp some important parameters of spark plugs. After fully understanding these parameters, I believe car enthusiasts will naturally know how to choose the right spark plugs for their vehicles.

Spark plug parameters may seem complicated, but we don’t need to focus on all of them. Only a few key parameters matter. Once we master these, selecting the correct and suitable spark plug products becomes very easy.

We’ll briefly explain the following parameters: spark plug heat rating, resistance, electrode gap, thread length, and understanding the various operating conditions of spark plugs in vehicles. Let’s go through them one by one.

• Spark Plug Heat Rating: This value is indicated by lowercase Arabic numerals. Simply put, it represents the temperature of the spark plug’s insulator tip (the part surrounding the center electrode). However, this heat rating number is not standardized across brands, and an increase or decrease in the number does not necessarily indicate a higher or lower temperature, which can be frustrating. What we need to know is that spark plugs have different heat tolerance levels. If we want to increase the heat rating of our spark plugs, we should replace them with spark plugs with a higher heat rating. This enhances heat resistance, allowing for greater heat generation and thereby improving the car’s performance. Typically, factory-installed spark plugs have a moderate heat rating, such as 7. For modified cars, due to increased engine performance output and higher operating temperatures, we generally recommend replacing spark plugs with a higher heat rating when the original ones near the end of their lifespan. This helps improve the engine’s working performance. However, higher isn’t always better. For example, if the factory uses a heat rating 6 spark plug, we typically recommend upgrading to heat rating 7, 8, or 9 spark plugs of the same brand, based on actual hardware and horsepower conditions. Avoid jumping too high, such as directly using a heat rating 10 spark plug. It’s also important to stick with the same brand as the original equipment manufacturer (OEM), as heat ratings are not consistent across brands. Some aftermarket spark plug brands have undergone repeated testing for specific vehicles, making them a straightforward replacement option. In simpler terms, modified cars require spark plugs with better heat dissipation due to the high demands of high-RPM engine operation. Therefore, choose spark plugs with a slightly higher heat rating than the factory ones. Note: For Champion and Bosch spark plugs, a smaller number indicates a higher heat rating, while for NGK and Denso, a larger number indicates a higher heat rating.

• Spark Plug Resistance: Spark plug resistance is designed to reduce magnetic interference caused by high voltage in the ignition circuit. Most modern vehicles use fuel-injected engines, which require high-resistance spark plugs. Only a few older cars (with carburetors) still use low-resistance spark plugs. Additionally, most platinum and iridium spark plugs available today are high-resistance. Therefore, when upgrading spark plugs for modified cars, resistance is generally not a concern, and the chance of selecting the wrong type is almost zero.

• Spark Plug Electrode Gap: This refers to the distance between the side electrode and the center electrode. Spark plug gaps typically range from 0.6mm to 1.6mm. Generally, a larger gap means stronger ignition capability, but there is a limit. Beyond this limit, ignition capability can be negatively affected. When upgrading spark plugs, we usually choose iridium or platinum spark plugs, which can be made very thin and have relatively low gap requirements. These spark plugs offer high ignition efficiency when new, but after about 20,000 kilometers, the center electrode may wear down, increasing the gap. While ignition may still occur, efficiency often decreases, leading to increased fuel consumption. This is why we recommend shorter replacement intervals for spark plugs in modified cars.

• Spark Plug Thread Length: This simply involves selecting the correct model, so we won’t delve into it here.

• Spark Plug Condition Analysis: This is very important. By examining used spark plugs, we can determine whether the engine is functioning properly and decide if further adjustments are needed.

  • A normally functioning spark plug will have a brown or grayish-white insulator tip, indicating proper combustion and compatibility with the engine.

  • An overheated spark plug will have a scorched white insulator tip and prematurely eroded electrodes. This is usually caused by insufficient heat dissipation or the use of fuel with a low octane rating. In such cases, it’s advisable to replace the spark plugs with ones that offer better heat dissipation, meaning a higher heat rating. Some might argue that better heat dissipation should correspond to a lower heat rating, but we’ll stick with better heat dissipation as the guiding principle. Since heat rating numbering varies by brand, focusing on heat dissipation is the safest approach.

  • A carbon-fouled spark plug will have black, fluffy carbon deposits. This is usually caused by insufficient air intake, incomplete fuel combustion, or excessive heat dissipation capacity of the spark plug, leading to inadequate self-cleaning. In such cases, it’s recommended to replace the spark plugs with ones that have slightly reduced heat dissipation capacity, meaning a lower heat rating.

1. How to correctly choose the right spark plugs for your modified car. Here, we focus on a few key points:

   • Select spark plugs with the correct thread specifications to ensure proper installation. This is the most basic requirement.

   • Choose spark plugs with the correct heat rating. This is very important and critical for the performance of modified cars. Refer to the heat rating of the factory spark plugs and try to choose the same brand. If your car’s horsepower has increased by no more than 10%, stick with the factory heat rating. For increases between 10% and 30%, choose spark plugs with one unit higher heat rating. For example, most Audi models use NGK spark plugs as OEM, with a factory heat rating of 7. In this case, upgrading to NGK heat rating 8 spark plugs is generally a suitable solution.

   • Next, choose the spark plug material: nickel alloy, iridium, platinum, or iridium-platinum. Most modified car enthusiasts won’t struggle with this decision, as the price difference is usually within a few dozen yuan per plug. It’s best to choose precious metal materials.

In summary, upgrading spark plugs is far more complex than it seems and often requires coordination with other hardware components to be effective. Simply replacing spark plugs with high-performance ones won’t increase horsepower; it only improves operational stability. Typically, after modifying the engine and enhancing performance, the ignition system is upgraded as an essential part of the overall modification process.

Upgrading spark plugs also requires upgrading to better ignition coils and high-voltage wires to form a complete system. Therefore, in the next installment, we’ll share insights on upgrading ignition coils.

Thank you for your support. If you’ve read this far, you’re a true friend and car enthusiast. If you have any questions, feel free to leave a comment, send a private message, or ask us directly if you’re unsure about which products to upgrade.