2nd Gen R56 Cooper S Spark plug heat ranges on stock vs tuned engines?

I've been doing a ton of research on tuning and adding mods to improve performance in our Mini Coopers, should those of us running more boost pressures, intake and exhaust systems with/without tuned engine be using a colder plug than what originally used when you purchased your Mini?

My thought is that I'm having pre-ignition because of excess heat leftover after the combustion process, this excess heat build-up is causing the newly air/fuel to ignite too soon causing pre-ignition periodically. That is why I'm asking this particular question regarding heat ranges of spark plugs.

Am I correct in assuming that when replacing your spark plugs with new ones that going with a colder plug than what was originally in your MCS is the best idea?

Thanks,
Systemlord.

 

To date I've had the dealer walnut blast my intake runners and valves on my Mini which was pretty bad and freed up a lot of snappy torque and overall performance. The combustion chambers (top of pistons) are covered in black carbon deposits, I used a bottle of BG 44K and the pistons are starting to show the aluminum alloy color of the pistons.

There are still more black deposits around the edge of the piston so I purchased two more bottles of BG 44K Fuel System Cleaner, I will purchase and use a bottle for every gas tank until I'm satisfied there is no more (carbon) pre-ignition. Then I will use it once a month or every other gas up.

At first the layer of carbon on the pistons was soft and dry enough to scrape off using the tip (2mm tip) of a Steelman Bend A Light Pro through the spark plug hole. After using just one bottle the layer of carbon started clumping up together and then was completely gone after going through another tank of gas without BG 44K. Now I have a second bottle of BG 44K in there, we shall see what happens after three bottles of BG 44K.

Does anyone know of a service offered for this kind of problem that would yield better, faster and more thorough results from some kind of service shop? I don't trust my dealer because they told me that they added something special to the tank after the walnut blasting, I don't see any indication that they did any such thing.

I really appreciate the responses guys!

 

I would indeed pay the price for 93 octane if I could locate a station in California, does the fuel system cleaner add anything that would help the combustion process be more efficient? The reason I ask is because when I was driving it today I really tried to get it to do pre-ignition by being pedal heavy when in low rpms which usually throws a bunch of gas and pressure causing pre-ignition. I'd like to buy ten cans of that BG Power Enhancer!

 

An excellent spark plug guide! The plugs that were in my car, the original plugs were the NGK-R ILZKBR7A 8G's (R5?), the new plugs I purchased are NGK-IR ILZKBR7A 8G's. I'm not sure what the R5 means, are these two plugs the same heat range? If so I'll assume these are 7's.

 

Why would a Cooper S come with JCW plugs and what are the differences between the two plugs?