Upgrading from NGK BPR9ES from BPR6ES.

[Chim55117]

I was doing some reading online and found that with higher boost applications, horsepower, and modification, the stock BPR6ES spark plugs are more prone to detonation.

Sometimes while driving the VR-4, I get backfires around 4-5K RPM. And to some extent this would make sense in relation to my problem (of backfires). I have access to free NGK BPR9ES, and was wondering since I should spring for them and install them.

Is there any any "downside" from me running plugs that are 3 steps colder? There are also the options of BPR7ES, or BPR8ES. I just want to make sure that if I run the BPR9ES it isn't overkill for my application.

The VR-4 has a 20G with full supporting mods and the like and 324 WHP at 18 LB of boost. Relatively low street/daily boost is what it is at now. During the summer I will likely crank the boost and retune with my DSMLink.

Thanks in advance,

- Stephen