DDP

I tried searching and I didn't come up with any answer to my question. What is the purpose to using 'colder' than stock spark plugs like the Beru S-9s? Is this for higher boost? Any drawbacks? Thanks

awilson40

The 'heat range' of a plug has to do with how quickly the plug transfers heat to the head.
A colder range plug will transfer heat a bit quicker so as to lessen the chance of detonation
do to a 'hot spot' on the plug...but only if thats why you are detonating in the first place
A colder plug in a mostly street car that spends a lot of time in traffic may tend to build up
carbon quicker.

Russ Murphy

Trying not to incite an "anti-detonation devices and the tooth fairy" thread, but since I can't see into the combustion chamber and it is a common practice that appears to help, then yes, colder plugs are an attempt to eliminate(or reduce) the plugs potential to contribute to knock. Drawbacks are ancedotal references to lumpy idle, etc.

Mike1982

I put in a set of colder plugs in my car and would like to go back to stock to see if any difference. My idle isn't the best, so many that will help correct it.

Jfrahm

Yes, the downside to colder plugs is that they do not get hot enough to burn off deposits on short trips in some motors. If you drive like a gramma (and not that old lady I tried to hang with on Mulholland) cold plugs are not for you.

-Joel.

awilson40

I have tried both and keep stock in due to mainly city driving.