OK. That is what I did. One coil for the front housing and one for the rear. Piece of cake. One reluctor, two pickups.

 

I took a look at the "SAG" seminar from Tech Welding's get together, and noticed that both leading and trailing plugs looked to have been badly overheated. The street plugs are very hot and only perform well because of the shielding. Higher numbers in NGK is going colder.

 

Racers use the 11.5 heat range. Very cold, fine wire center and nearly fine wire ground electrode. Gapped at .010" regap back to .010"

when they get to  .015" one time then discard. $25.00 each.

 

Let me dispel some common knowledge. Racing engines must endure

very high stresses induced by high power output, high heat and high revs (9,600 RPM). But they have modest duty cycles. About 75%. They spend much time at high revs and fully closed throttle. As in braking from 146 (our best) driver screaming fogging his visor, both feet on the brake pedal. Other times its just up and down through the gears and much of that will show up as closed throttle. When we look at data after a session we are looking to minimize closed throttle time. Not much racing going on at closed throttle.

 

Airplanes have duty cycles very close to 100%. Wide open throttle for hours on end. A much higher degree of difficulty. Mostly problems with heat rejection as you read about here every day. And the need for a hot street plug to keep the deposits away may not exist. I would go way cold and back off of that only if fowling actually becomes a problem.

 

If the Mazda dealer has it in stock, it is probably too hot.

 

If one of those electrodes is square ended new, it should still be square ended when you throw it away. None of that melted to round stuff.

 

All sorts of things come up when the plugs are too hot a heat range, and they are all bad.

 

Lynn E. Hanover

 

My initial design is essentially a single coil firing
two plugs in the same chamber simultaneously.