msonbolg37x

My car is boosted with the stillen kit. I'm looking to upgrade my spark plugs to the GTR plugs. would i need to retune or no? i've heard mixed answers.

goredcar

Do you need GT-R plugs for the SC? I thought this was only required if you went with a turbo? I spoke with Stillen when I did my V3 kit last year and they did not suggest different plugs. I put in new plugs prior to my tune but stayed with the OEM ones.

ANMVQ

iTrader: (13)

Yes you do need them rule of thumb is for every 100 HP you will need a heat range colder plug. I ran the GTR plugs in mine with the Stillen SC- but no retune

Waste86

Yes they are good to have. No you don't need to retune.

goredcar

So yet more bad advice from Stillen... I had pretty much forgotten about my nightmare with them last year and it now all comes flooding back. Thanks for this ANMVQ and Waste86. Here is a NGK article that is quite detailed:
https://www.ngk.com/learning-center/...or---do-i-need

msonbolg37x

thanks for the replies guys and great article goredcar!

msonbolg37x

I've called a few tuners and they've given me mixed answers. Some say you need a retune and some say I don't. I think I'm just going to be safe and change them with OEM plugs. I'd change to the GTR plugs and tune it if i had a tuner in my state

Waste86

All the plugs are doing is preventing pre-ignition by going a step colder. There is absolutely no effect on the tune. the only time this would come into play is if you are running way out of heat spec plugs (say running really hot and pre-igniting a lot) and then going to a colder plus will buy you some more leeway on the pre-ignition, and you may be able to adjust your timing tables slightly more aggressive. That is just treading such a fine line that I did not consider it worth mentioning, as you want more fail safe to avoid knock. If I am wrong, someone please let me know.

goredcar

Hi guys... I spoke with my tuner after this discussion and he said that he did recommend a colder plug... and that no retune is required. So I ordered a set of GT-R plugs from an ebay vendor and they just arrived today. I was a bit startled when they were exactly the same as the OEM ones that came out of my car when I installed new plugs for the SC install. OEM for the G37 is Denso FXE24HR11. I looked up GT-R plug and it is the exact same plug. I called Concept Z and asked them and they recommended a NGK93026 (heat range 8) which is exactly the same as the Denso heat range 24. See Spark Plug Cross Reference HEAT RANGE CHART

So now I am the proud owner of a new set of plugs that I don't think I need. I am really surprised that the GT-R plugs are the same as ours.

Waste86

To be honest, I was going to chime in and say that the heat ranges are different for the plugs. However, the information I have found seems to say they are the same heat range. The NGK has a smaller gap (.03X compared to .044 of our Denso). I kept hearing they were a step colder, but I can find nothing that supports that.

goredcar

Heat range 8 for the NGK = heat range 24 for Denso. I know of a Z turboed to over 500HP running the denso range 24 plugs with no problems. I am stunned how misinformation gets passed around on these forums and accepted as gospel. Everyone saying get GT-R plugs and they are exactly the same as OEM for Z or G37

Waste86

I mean, they ARE different, but everyone says it is the heat range, but that does not appear to be true. Gap seems to be the major difference I would be interested in clarification on this as well.

slartibartfast

iTrader: (7)

Going forced induction generally warrants smaller plug gaps due to higher charge density. Heat range is not so cut-and-dry. Cool enough to prevent pre-ignition yet hot enough to prevent soot build-up.

Waste86

I can understand the smaller plug gap. However, everyone seems to go them because they are told they are a heat range colder than stock, which does not appear to be true.

slartibartfast

iTrader: (7)

Run the plugs you want for a few thousand miles and check them for electrode erosion and soot. If no soot, repeat the test with a cooler plug. Keep repeating until the car starts to mis-fire or the plugs begin to develop soot. You know you're one range too cold then.