So ive just spent the last two hours reading through threads regarding spark plugs as im in the middle of a 400whp build. The common consensus seems to be either B10EGV or the Ngk R6725 - Both of which are conventional spark plug designs with the single strap which has been known to fly off and chew up motors (and fairly commonly from what ive read) Yet they still seem to be the go to spark plugs.

Can anyone confirm if this is actually a concern to be taken seriously and if there is a rotary spark plug that can also provide adequate performance.

 

I used to use the 2 stroke snowmobile? NGK BR10EIX.

I am now using a plug Mazdaspeed/Mazda Motorsports recommends for the application.

Mazda part#
Of course other heat ranges are available-
11 is pretty cold. The 11s do foul on prolonged idle and driving around town under 2,500rpm. When a leading plug fouls out it feels like you lost all the side seals on the rotor- boost comes up super easy but no power till it clears.

They are about $18ea through regular retailers, some discount with Mazda Motorsports account.

 

The single ground NGK racing plugs are the best but expensive. But they run soooo much better. The NGK other plugs can be used but with a shorter plug reach do not fire as well.

 

NGK R6725-105 is what I prefer over a bar of boost. It is a 10.5 heat rang plug. Over 25lbs I use the -110 which is a 11 heat range. There is also a -115 which is an 11.5. The higher boost you run, the colder plug you need. I personally am not a fan of the snowmobile plugs as you need a special thin walled socked and I found that while they do work, they foul quickly. Keep in mind that the colder the plug, the poorer the car will run and the quicker they will foul. With the 11s and 11.5s I recommend warming the car up on 9s then switching. Not very convenient so I don't use them except at the track

 

So mazda recommends a single strap plug?

 

I don't know if Mazda Motorsports recommends a single strap plug for other applications.

The NGK R6601-11 I have listed that they recommend for Street and Peripheral Port RX-7 and RX-7 Twin Turbo is surface discharge plug like a stock spark plug.

 

Hey BLUE TII - what made you change to the NGK R6601-11 instead of the NGK R6601-10?

I am currently running the BR10 EIX, but after reading your comments (and my hatered of using a thin walled socket) I was thinking to change to the NGK R6601-10, this should work right?

Thanks!

 

Simply because I was erring on the safe side with racing my new crate motor and new set-up maxing out the stock injectors. I also was running it on 104 unleaded.
Once I had some miles on it I did some 4th gear full load pulls and sure enough it was creeping to 17psi, running mid 12s AFRs and hit max duty cycle when it was cool out in the evening.

I tried out a couple exhausts and got rid of the boost creep and now running 14psi and AFRs in the 10s.
I might go to R6601-10 if the fouling gets so bad it doesn't clear-up easily like it has been- but this is just a race car that I drive to events.

NGK R6601-10 should be a great replacement that gives you a little more peace of mind over the BR10EIX.
I can't telly you how long they last compared since they are plain Nickel thick electrode VS the Iridium fine wire electrode. But on my BR10EIX it was the ground strap gap that wore fairly fast anyways.

 

Awesome - thank you! Just ordered a bunch!