I have a gsr block with USDM ITR pistons that gives me 10.8-11.1 compression. Cams, IHE, tuned on crome to 192 whp. What kind of spark plug should I use? I've been using the Denso Iridium spark plugs for just the regular GSR and its time to replace them so I've been looking to buy the same ones again online am not sure if should go one step colder or not.

Do I need to run one step colder? Also, should I get them for the GSR or for the ITR since my block and cams are similar to the ITR? Should I look into NGK or anything else? And where is a cheap place to get them online? thanks in advance guys.

 

btw, when my car was tuned, I was using the regular GSR Denso Iridiums.

 

I have a 1999 GSR with USDM ITR Pistons. The head and block have been milled/decked and I'm at about 11.6:1.
I run ITR Stock NGK Plugs. NO issues. Tuned on Hondata S300 in a P72.

 

go do a full pull and shut down at peak rpm. coast the car to a stop and pull the plugs

look at the groundstrap and only go 1 step colder if you need to.
i believe gsr's are heatgrade 6, you can probably use a 7, but only your engine knows