SPARK PLUG GUiDE!
 

(If you’re skeptical about using something else, or do not plan to use something else, nothing is wrong with staying OEM, however this is meant to be informative, not a flame, troll thread).

Hello everyone,

I’ve been researching on spark plugs recently, and bought my NGk 2309 iridium ix plugs, however they didn’t fit and I was SOL. Been chatting with a buddy Ryan of mine, who’s been looking up specs as well, and decided to make up this thread. Some stuff has been covered but I’m trying to compile all in one page so you don’t spend hours researching not knowing what to buy, and so you don’t have to clean off your plugs til you can get to a dealership because it’s sunday and they’re closed, and most autopart stores will not have what you’re looking for.

(I’m no expert, mechanic, or anything of the sort) I love cars and researching stuff, if you are one of those however please give me your professional answers, I love to learn new stuff.

Turns out our cars use
12mm thread x 26.5mm length
the head is a 14mm
Gap is 0.8mm/0.031”
Electrode position at 8.5mm seems pretty important too, this makes me skeptical about interchangability.

Denso
ZXE27HBR8 - this helped me a lot thanks to their pn.
Precious metal Z: 0.55mm diameter iridium
Thread and hex XE: 12x14.0
Heat range: 27
Reach: it’s confusing but you’re looking for 26.5mm total length,
19.0 mm
(Electrode position: 8.5 mm)
26.5 mm
B: triple ground electrode
R: 10k ohm resistor
8: 0.8mm/0.032” gap

Denso Iridium tough (look like an economy version)
VXEBH27

NGK

97537 racing plug
I believe this will have to be gapped, they look extremely close, and their specs online say 0.032mm pregap, these will need a ton.
(I will be installing them this weekend)


NGK 93026 laser platinum iridium (GTR) plug
the heat range is actually hotter than our stock ones, but uses the same gap. HKs has an article about it as well. That being said, it should be safe to go find yourself some economy R35 GTR plugs for those who care about gas milage and are in that vehicle for economical reasons.. ��

C63 AMG use the same specifications as well but are 0.044” gap.

HKS (you want the HL type)
HL Type φ12×26.5mm 14mm NGK #8 SUPER FIRE RACING M40HL 50003-M40HL (one step hotter)
HL Type φ12×26.5mm 14mm NGK #9 SUPER FIRE RACING M45HL 50003-M45HL (OEM heat)
HL Type φ12×26.5mm 14mm NGK #10 SUPER FIRE RACING M50HL 50003-m50HL (one step colder)

Champion spark plugs, couldn’t find any measurements on them, it may be just the gap that is the same as Fa20 requires, so it pops up under many universal part searches.

Champion 7445 double platinum I’ve confirmed will fit.

Hex Size (mm): 14mm
Thread Size: M12
Thread Reach (In): 1.043 Inch
Number Of Ground Electrodes: 1
Preset Gap (In): 0.039 Inch
Preset Gap (mm): 1mm
Resistor Plug: Yes
Center Electrode Tip Material: Platinum
Heat Range: 4
Insulator Height (In): 0.118 Inch

Heat range is equivalent to NGK’s 9 and Denso’s 27.

I hate Bosch plugs had a bad experience with them before, so I won’t be adding anything, feel free to though.

Getting lazy now, so calling it quits. If you’ve confirmed anything else works or tried the gtr ones, etc. chime in! My only options I knew of before this were OEM, NGK racing, or HKS plugs.

Retrofit plugs at your own risk, I’m not responsible if you mess your car up, or use Bosch plugs.

plugs
 

how did the 97537 plugs work out...
notice any differences?

Not really honestly, my plugs were in pretty good shape before I replaced them, felt like it idled smoother though

What year c63 amg?
Have you tried NGK 6043?
Would it be better to have one with lower or higher heat range?

What is the factory OEM plugs? VXEBH27?

ZXE27HBR8

I just bought a set and have they next to me in my desk to verify.

Whats different between the two denso plugs.

Since both are Iridium and the ZXE doesn't show up in Denso's part book, I think maybe the ZXE plug is made specifically for Subaru and the VXE is the Denso direct equivalent.

The only difference I can find are maybe the ground electrode and the resistor.

OEM = Triple ground electrode (not sure of metal), 10ohm resistor

VXEBH27 = Copper ground electrode, 5ohm resistor.

I think it's also very possible the VXE P/N supersedes the ZXE P/N.

I also noticed that NGK racing plug has a 5ohm resistor as well and but a smaller gap (Because racecar). I think if I bought the NGK racing plugs I would not alter the gap as they are made specific for these cars with that gap in mind.

Hks spark plugs
 

So my question is which HKS spark plug is better the 40,45 our the 50?

the only difference between VXEBH27 and ZXE27HBR8 is the resistor. One is 5k Ohm, another is 10k Ohm.

How does the difference in resistance affect the engine?

I don't think it has to do with engine performance, but electrical noise.

IMO, that may very well be the answer but I'm no sparkplug expert. For all I know, resistors are used to reduce noise. However, I cannot speak as to what effects having higher or lower resistance achieves.

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From the NGK website.

FYI, Just bought Denso 3536 from RockAuto. $13/ea. bar code has ZXE27HBR8..

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