I've noticed a lot of places sell cold spark plugs for the ST and I was wondering what the difference is between those and the stock ones. Why I would want to put those plugs in my car?
Thanks...One wants a 'correct spark plug for the conditions inside the cylinder.
The stock plugs are suitable for the average driver.
Colder plugs are for high performance use. IE: racing. Or the driver who is basically racing around all the time on the street.
The colder plug is for hotter cylinder conditions. Where the engine in under high RPM and heavy boost most of the time.
A 'colder' plug allow more heat to escape via the plug body. And thus stays at the correct design temperature in a 'hot' cylinder environment.
For the average driver, installing cold plugs will not be of any benefit at all. The colder plug will not warm up properly, and the colder plug will get full of deposits and STOP WORKING correctly in an engine not run hard all the time.
Read this and take the time to educate yourself.The heat range must be carefully selected for proper spark plug thermal performance. If the heat range is not optimal, then serious trouble can be the result. 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)
With respect to the previous posters, here is the short version:I've noticed a lot of places sell cold spark plugs for the ST and I was wondering what the difference is between those and the stock ones. Why I would want to put those plugs in my car?
Cut and Paste"Fun Facts"
The difference between Hot & Cold for plugs is the length of the insulator between tip & contact with the metal "shell" of the plug.
Long insulator stays hot, because of the long path heat has to travel before reaching the colder wall of the shell.
For an extreme, some "Racing" plugs have an almost flat insulator at the tip - heat path straight to the wall to cool it as much as possible.
Peek inside the business ends of a few plugs to see the differences in how long that insulator might be.
Thanks, sometimes crayons come in handy.Harder to explain this in words than pictures. The cylinder head is the "cold" part compared to the plug tip. The less insulation between the tip & the head the "colder" the tip will stay. The porcelain is the insulator (electrical & heat) between tip & plug shell, which screws into the head to transfer heat/electricity.
Touch an ice cube with a sheet of paper between it and your hand - feels cold right? That's heat transfer through a small insulator. Do the same using a phone book - virtually no heat transfer, just as there's little through a LONG spark plug insulator.