Explaining the Spark Plug options for the FSI / TSI Engines

With so many spark plug choices available for the FSI and TSI engines, it can be difficult to determine which plug is right for your application. Today I am going to discuss the differences between the NGK spark plugs that we offer.

We can classify the spark plugs by two different options: Material and heat range. In addition to that, we can look into different spark plug gap options, and see how that can affect your spark plug choice.

There are many different materials used when discussing spark plugs, but we are going to focus on three common choices today: Copper, iridium and platinum.

Copper spark plugs are the most common and the most cost effective, but they do present a definite drawback in direct injection applications. The fuel is sprayed directly into the combustion chamber at extremely high pressures, which causes rapid erosion of exposed copper. A standard copper spark plug does not last very long when used in a direct injection engine.

Next up we have both iridium and platinum. The electrodes of these plugs are coated with their respective materials, which both hold up much better against fuel erosion. There are benefits and drawbacks to each, however.

The primary difference is the price. The iridium plugs are cheaper than their platinum counterparts, and not without reason. Each spark plug has two electrodes, a firing electrode and a ground electrode. In the iridium plugs, the firing electrode is iridium plated, while the ground electrode is still bare copper. NGK’s double platinum plugs are platinum plated on both electrodes. What this means is the iridium plugs, while longer lasting than the bare copper, also suffer from a reduced lifespan when used in a direct injection application. Only the platinum plugs can offer reliable long life service in FSI and TSI engines.

However, if you are using any sort of water/meth injection, it is highly recommended that you use iridium plugs instead of platinum, as methanol can react poorly with platinum. If this is the case, then the reduced service life of the plugs must be considered and acceptable maintenance item.

The next consideration is heat range. The heat range is a measure of how quickly the spark plug will transfer heat from the electrode into the surrounding metal of the cylinder head. If the heat transfer is too quick, the spark plug will run cold, and will foul up. Too slow of a heat transfer, the plug will run hot, causing damage to the insulator and creating a hot spot in the cylinder.

The original heat range used in FSI and TSI engines is a seven. This is what we recommend for most stock turbo applications, regardless of tune.

Cars with larger turbochargers can see higher combustion chamber temperatures, and can benefit from running an eight heat range. This includes K04, stage 3, and even tuned Golf R/TTS cars.

Finally, there is a question of the proper spark plug gap. The simple answer for this is that the proper gap is the largest gap you can run without experiencing misfires. With increased combustion pressures, this often means having to run a smaller gap than originally specified. The stock gap specified ranges from 0.032” in the FSI engine, up to 0.043” in the TSI engine. Many tuners recommend running a gap of 0.028” or smaller when using their software. However, when using a more robust ignition coil, such as the R8 ignition coil, you can safely run the original gap in most applications.

Here are the plugs we offer for FSI and TSI engines, along with the recommended application.

PFR7S8EG – A double platinum spark plug with a seven heat range. This is the stock spark plug, and it fully meets the specifications set forth by Volkswagen/Audi. Volkswagen/Audi specified a different resistance to work properly with their ignition system components without causing interference. Therefore, the spark plugs ending with -S8EG are the most reliable plug when used with any OEM ignition system. This is our most recommended spark plug for any stock turbo application, especially when paired with the R8 ignition coils, as this will allow the use of the stock spark plug gap.


PFR7B / PFR7Q – Both are double platinum spark plugs with heat ranges of seven. Although they do not carry the same Volkswagen/Audi specification, they have proven to be reliable when used in the FSI and TSI engines. So, what’s the difference? The PFR7B has a recommended spark plug gap of 0.028”, while the PFR7Q has a recommended gap of 0.032”. NGK does not recommend adjusting the spark plug gap greater than 0.008” from the base specification. So, if you need to run a smaller gap, use the PFR7B. If you want to run a larger gap, use the PFR7Q.


BKR7EIX – An iridium spark plug with a heat range of seven. This is an ideal spark plug for stock turbo applications running an additional fuel system, such as water/meth. Expect reduced service life, however.


BKR8EIX – An iridium spark plug with a heat range of eight. This plug is being recommended for use in big turbo systems, as it is the most readily available eight heat range plug, but it also suffers from a reduced service life. It is ideal for big turbo applications using water/meth injection.


PFR8S8EG – A double platinum spark plug with a heat range of eight. This is the only plug in NGK’s double platinum range that carries both an eight heat range and Volkswagen/Audi’s -S8EG specification. This is the spark plug we most recommend for use in a big turbo application, as it offers the best quality and longest service life.