I just found out that NGK recently discontinued the Racing grade spark plugs for our cars (part number: R2556B-9). The NGK Racing spark plugs have been well received by our community (http://preview.tinyurl.com/n37kmg4). I also checked NGK's official site and it also no longer lists the Racing product for our cars.

What are some alternatives to the NGK Racing for our cars that can support great performance and are made with great quality?

 

So, the way I read that page is that the R2556B-9 has been discontinued and replaced with R2556G-9

They are available on eBay
1x NGK RACING SPARK PLUG R2556G-9 (Old PN R2556B-9)
If you contact Nengun (from your pic) I bet they could get 'em

 

Standard replacement NGK's work fine...

 

Here is my running list:

OEM
NGK ILKR8E6 (earlier)
NGK DILKR8B6 (later)

“Upgrades"
NGK Racing R2556B-10 (heat range 10)
Now R2556G-10
NGK Racing R2556B-9 (heat range 9)
Now R2556G-9
NGK Racing R2556B-8 (heat range 8)
Now R2556G-8
HKS M45XL (heat range 9)
HKS M40XL (heat range 8)

 

Thanks everyone here for the spectacular insight!!

If I understand correctly, the upgraded OE replacement spark plug DILKR8B6 has a heat range of 8. What is the ideal heat range to use for, say, a bolt-on and protuned Evo X (~340 whp)? Is heat range 9 necessary? Or is heat range 8 more than sufficient for that application?

A quick search shows there is simply not much discussion of this on the forum to make it conclusive, but historically most pros(?) seem to recommend sticking to heat range 8:

Again, Bryan, I appreciate your awesomeness of posting this list here, which makes the community awesome.

 

Haven't had an issue running OEM replacements in 600+ whp cars.

 

I ended up getting NGK Laser Iridium spark plugs (updated version, heat range 8, p/n DILKR8B6) for about C$150 per set.

I also quoted HKS M-Series Super Fire (heat range 8, p/n 50003-M40XL), which is ~C$220 per set. NGK Racing (heat range 8, p/n R2556G-8), which is ~C$210 per set. As the Laser Iridium is the cheapest and supposed to work very well with a stock engine, I went for it.

 

As an FYI, you can get them for WAY cheaper (about $80 USD) if you look.

 

I know, right? But here in Canuckistan, trade protectionism is a real thing. It made me kind of regret that I should have ordered them in the States when I travel there next time.



^^^^Speaking of the plugs, I just removed the old ones that came with the car (also DILKR8B6). They've had about 40k miles with stock tune, but look quite worn. Nevertheless, according to the quick guide picture below, they are at least operating normally. The engine now runs SOOOOOOOOO much smoother with the new plugs, it's like how you cast a spell, polymorphing a 20-year old Corolla to a new Cadillac.



^Source: https://mechanics.stackexchange.com/...-my-spark-plug