Spark Plugs
 

So like many of us here, I run GTR plugs. I went and dig some digging, and the specs of our stock plugs vs the GTR plugs are just the gap.

I crossed referenced it on NGK's website, and checked out the specs. The plugs themselves are the same material and everything, just the gap differs from .44 and .32

With that being said, how many of us boosted guys are still on stock plugs? I (like most) changed mine preemptively changed mine when the supercharger went on.

Side by side of my OEM vs the OEM GTR plugs I put in when I transitioned to the boosted life.

Nissan OEM NGK DILKAR8A8 Iridium Spark Plug - Nissan GT-R R35

Even in your photo you can see that the gaps are different. I mean why on earth are we spending 100+ on plugs when our stock OEM ones with a regap will work? I know in the grand scheme of things, this is a drop in the bucket, but if you can save money, you should save it, right?

I was at 65k miles when I converted, so I felt like it was prudent to knock out the change while I was in there haha.

I don't know what newer plugs are like, but it used to be that plugs were single-use because of the design of the gasket. So, if you removed them to re-gap OEM plugs, you'd essentially ruin the gaskets for re-install.

If that still holds true, that means you're comparing a price point for new OEM Z plugs against new GTR plugs...

What is the heat range of both plugs? One is a Denso and one is a NGK. A boosted car should run a lower heat range to help with knock.

When I went boosted I used the OEM plugs for over a year with no issues ...I did switch over to gtr plugs ....how ever I believe the gtr plugs are one step colder and more resistant to detonation

I installed stock plugs and regapped them, so far so good. Will keep you guys posted.

They are both 8 heat range.

So I just completed an auto x over the weekend, and had no issues with the stock plugs regapped.

I did a few datalogs while on track, and saw no realdifference. So save your money guys! Just regap your stockers

I thought the reason that people don't regap iridium plugs is that the iridium bit is fragile and can easily be damaged during regapping?

it's honestly because people do it incorrectly. Take a feeler strip, and take some needle nose pliers and slowly bend it in and it's totally fine. I've done it this way for years.

You would need to data log it to see what the knock sensor was seeing. It may be because of you tune if you had it done with stock plugs that you saw no difference. The rule of thumb is to reduce one heat range for every 5 psi of boost.

I tuned my car on GTR plugs, and I datalogged knock....I have the knock flash warning as well.

The real question for me here is the heat range of the GTR plugs... most of us switched to them thinking they were one step colder. OP's research says that is not the case. Anyone verify?

That's what the 8 specifies in the part number, but I pulled it from NGK's own website (well it links you to another parts website).

The real question is the factory plug is a Denso. What heat range were those. Mind you that plug heat range reading can be different. NGK are read one way, and Bosch are read another. Been a while but that is what I have experience with in the past.

Heat range and gap are two totally separate things. The smaller gap is needed because when the engine is under boost the air density in the combustion chamber goes up. Because air is an insulator the gap needs to decrease so that the spark can be generated with the same amount of voltage but with denser air. I hope that explanation makes sense.

Heat range is all about the center electrode temperature. If you look at a hot plug verses a cold plug you will see the hot plug has a longer center electrode ceramic part. This longer heat path to the cylinder head allows the tip to remain at a hotter temperature (less heat loss back to the head). A cold plug is just the opposite, it has a short ceramic part that transfers the heat to the head quicker which keeps it cooler.

A hot plug is typically used on a low compression engine that sees light loading (grocery getter) where the cold plug is for high compression high load use. The cold plug will keep the tip from getting so hot that it will ignite the fuel air mixture before the plug fires. That will cause detonation. At least that is what I have been taught.