What Spark plugs should you use? It's a very common and important question.
| The spark plug heat range has no relationship to the electrical energy transferred through the spark plug. The heat range of a spark plug is the range in which the plug works well thermally. The major structural difference affecting the heat rating is the length of the insulator nose. A hot type spark plug has a longer insulator nose. The insulator nose of a hotter spark plug has a longer distance between the firing tip of the insulator, and the point where insulator meets the metal shell. Therefore, the path for the dissipation of heat from the insulator nose to the cylinder head is longer and the firing end stays hotter. The insulator nose of a hotter spark plug also has a greater surface area that is exposed to more of the ignited gases and is easily heated to higher temperatures. A colder spark plug functions in an opposite manner The heat range must be carefully selected for proper spark plug thermal performance. If the heat range is not optimal, performance suffers, plugs foul out or end up damaged and possibly causing damage to the engine. The optimal firing end temperature is approximately between 500?C (932?F) and 800?C (1472?F). The two most common causes of spark plug problems are carbon fouling (< 450?C) and overheating (> 800?C). If you keep on adding timing until your finish MPH falls off but you still have no color on the plug?s ground strap but the porcelain has good color then your plug is too cold. If you have lots of color on the ground strap but the porcelain is clean and white then the plug heat range is too hot. The heat from the plug is cleaning of the fuel ring from the porcelain. Too often a plug that is too cold is used. One of the main jobs of a spark plug is to remove heat from the combustion chamber/cylinder head and transfer it to the cooling system. If too cold of a spark plug is used, the plug will not reach optimum operating temperature. When this occurs, the spark plug can not self clean and will quickly foul. Therefore if you run higher boost at the track, and lower boost during normal daily operation, you should use the appropriate heat ranges for each. A colder plug for the track, and a hotter plug for the street. We all too often see customers using spark plugs that are way too cold for the application. It is as if people like to be able to say "I run heat range 9 plugs", using it as some sort of chest thumping look at me, when in reality, your choice of spark plugs depends on the power your engine is making, and the fuel it is using. |
During tuning it is easy to accidentally fuel foul the spark plugs. This will be evident by a spark miss/rough under boost acceleration, and a black thick ring at the base of the ceramic nose deep in the spark plugs base (not visible unless using a bright pinpoint light and looking down into the spark plug). This makes copper spark plugs a better choice while tuning as they are cheaper to replace. Once a spark plug is fuel fouled it needs to be thrown away. There is no "cleaning" to repair the damage. The ceramic insulator becomes glazed causing misfires/arcs where there shouldn't be. This writeup is for the Mitsubishi 3000GT/Dodge Stealth For Stock boost (10-14psi) and Non Turbo setups (click here for list of suitable plugs) -Heat range for NGK plugs is 6. -Stock spark plug gap is .044" - Gap plugs down to .032" to avoid spark blowout -You should avoid regapping Platinum or Iridium plugs as the fine wire electrode is thin and brittle and can snap -What 6 heat range plugs fits your needs depends on budget and how often you want to change plugs. -OEM or OE replacements are platinum, which are great for stock boost and will last 100,000 miles. But they are pricey. -Iridium spark plugs will offer 60,000+ miles before needing to be changed. -NGK Copper plugs offer all the performance, at a lower price, but will require replacement at around 12,000 miles. For BPU (14-20psi) and Non Turbo 10:1 running 10psi-14psi (click here for list of suitable plugs) -Heat range for NGK plugs is 7. -Gap plugs down to .032" to avoid spark blowout -You should avoid regapping Platinum or Iridium plugs as the fine wire electrode is thin and brittle and can snap -What 7 heat range plugs fits your needs depends on budget and how often you want to change plugs. -Iridium spark plugs will offer 60,000+ miles before needing to be changed. -NGK Copper plugs offer all the performance, at a lower price, but will require replacement at around 12,000 miles. For 22+psi and Non Turbo 10:1 running 14+psi (click here for list of suitable plugs) -Heat range for NGK plugs is 8. -Gap plugs down to .028"-.032" to avoid spark blowout -You should avoid regapping Platinum or Iridium plugs as the fine wire electrode is thin and brittle and can snap -What 8 heat range plugs fits your needs depends on budget and how often you want to change plugs. -Iridium spark plugs will offer 60,000+ miles before needing to be changed. -NGK Copper plugs offer all the performance, at a lower price, but will require replacement at around 12,000 miles. For E85/Ethanol and or using an HKS Twin Power Ignition System Click Here! -It is HIGHLY recommended if using E85/Ethanol to use a non projected tip spark plug. This is due to preignition that can occur when using a projected tip spark plug and ethanol/alcohol fuels. -It is also HIGHLY recommended by HKS and Ninja Performance to use a resistor type spark plug if using the HKS Twin Power, which we highly recommend if boosting over 20psi to avoid spark plug blow out. -The Copper NGK BCR8ES gives you a non projected tip with a resistor plug. They are not a United States market spark plug in the 5/8" hex required for the 3000GT/Stealth. But Ninja Performance imports these spark plugs direct from NGK Japan for it's customers. -You can use this plug at any boost level over 18psi to 30 psi (over 30 psi you may do better with a 9 heat range NGK Copper plug) while using alcohol based fuels or any other fuel as long as you don't baby it around town for extended periods of time to avoid fuel fouling. Or get a set for track only use and use 7's on a daily basis. For 30+psi and Non Turbo 10:1 running 24+psi (click here for list of suitable plugs) -Heat range for NGK plugs is 9. -Gap plugs down to .024"-.028" to avoid spark blowout -You should avoid regapping Platinum or Iridium plugs as the fine wire electrode is thin and brittle and can snap -What 9 heat range plugs fits your needs depends on budget and how often you want to change plugs. -Iridium spark plugs will offer 60,000+ miles before needing to be changed. -NGK Copper plugs offer all the performance, at a lower price, but will require replacement at around 12,000 miles. -It is HIGHLY recommended if using E85/Ethanol to use a non projected tip spark plug. This is due to preignition that can occur when using a projected tip spark plug and ethanol/alcohol fuels. |