R7437-9 vs R7438-9. Which NGK Plug is better suited?

[Porra46]

Hi guys.

Well found that guys use either the NGK R7437-9 or the NGK R7438-9 plug.

Both must be gapped to 0.024"

Any particular difference between the 2 and which would be best for my Unitronic tune?

Sent from my SM-G975F using Tapatalk

[o1turbo30v]

If running stage 1, 1+, or 2. Use the stock OE plugs. NGK 91006, (SILFER8C7ES)

[tegxsi]

R7437-9 has been the recommendation and these have a projected center electrode. The ceramic portion extends out.
R7438-9 is a non-projected design and the ceramic doesn't extend past threaded portion. I'm not sure if the gap can be adjusted on this particular plug due to the ground strap design. Maybe someone can chime in on this...

Projected design runs hotter and should be better for ignitability. The OEM plugs are projected.

Brisk Racing ER10S has become popular option because of the cost. This is a non-projected plug.

I don't think anyone has had issues with R7437-9 so just stick with that. OEM plugs can work fine but If you drive your car hard or track it regularly then I would run a colder plug.