Modifications and Spark plug considerations:
These are observations that have been made by us or passed on to us. This information is a generalisation only. Your Nitrous fitter should be able to advise you on a suitable set of plugs for your vehicle.

1. Try to avoid platinum (particularly double platinum) plugs. There are suggestions that a chemical reaction may occur and some unusual deposits will form on the electrodes - these may impede ignition performance. Double platinum plugs (where a platinum 'chip' is welded into the ground electrode) may be at risk from the platinum chip becoming detached in extreme temperatures, the surrounding electrode material will doubtless have a lower melting point. A platinum chip dropping into the combustion chamber could be disastrous.

2. Try to find a plug with a short ground electrode. This is generally thought to be more important than a colder heat range. Because temperature will increase so severely and quickly when using nitrous oxide, the temperature at the tip of the plug's ground electrode will become extremely hot very quickly - the longer the ground electrode, the longer it will take for the excess heat to be conducted away from the tip to the plug shell and ultimately into the cooling system. An overheated ground electrode tip can cause detonation and may even fail completely.

3. Try to find a 'non projected' plug. The design of a projected plug will usually aid ignition performance at low engine speeds by moving the spark position closer to the centre of the combustion chamber, the downside of this is that the centre electrode and central ceramic insulator become exposed to combustion gases and hence are at risk of damage under extreme conditions. By using a non projected or even a retracted spark position, the firing tip is more protected and plug failure is less likely. A non projected or retracted plug by design will have a shorter ground electrode which is beneficial for the reasons mentioned in 2. above.

4. Use a non resistor or Iridium type plug if available. Please note if your vehicle manufacturer recommends a resistorised plug as standard we would not recommend using a non resistor plug, interference with engine and safety management systems may result! Some plug designs are only available with integral resistors. By using a non resistorised type plug, the amount of voltage available at the plug's firing end is slightly increased and therefore the risk of misfire under load is reduced. If combustion conditions are particularly extreme then an increased 'spark jump' voltage is required. Effectively, when more fuel and oxygen are compressed in the combustion chamber (as occurs in nitrous/turbo/supercharger use) the result will be similar to that of increasing the plug gap - if the gap becomes too large for the available voltage then the spark simply won't be able to jump the gap. Iridium spark plugs can help as they have a greatly reduced firing voltage (despite an integral resistor) - lower overall than most copper non resistor plugs. High performance ignition leads (such as Magnecor KV85 leads) can also help supply maximum available voltage to the plug.

5. Use a colder heat range plug. While colder plugs will be of limited worth during a large, short burst of nitrous, they will help to return the sparkplug tip to a safer operating temperature more quickly in between or after nitrous use. The intense heat of nitrous burn will not have time to be dissipated much more effectively by a colder plug in the usually short space of time for which nitrous is injected. A short ground electrode is more useful for maintaining 'safe' conditions during nitrous use (see 2. above)

6. Learn by the mistakes of others. There are no applications guides of suitable plugs for nitrous equipped engines. Web forums are a valuable resource when trying to identify a suitable part to use. It's unlikely that you will be the first to have a nitrous system fitted to your particular engine type. Do some research and try to find out what has worked for others and, perhaps more importantly, what hasn't worked.

General notes:

Consider carefully what plugs you intend to use. Bear in mind that the standard plug installed in your engine by the manufacturer will be ideal for normal use, any change of plugs to improve performance and safety under extreme use will almost certainly detract from performance under low load/cold starting/low rpm. Ideally you would have a set of standard plugs for daily driving and change to a set of 'safer' plugs for extreme use such as track days/racing etc. This rarely happens so a trade off between daily driveability and high performance/engine safety is required.