Some observation on Mazda rev C coils. I had read that these were to last longer than previous revisions, and for the sake of experiment, I replaced a set of these installed (to my best knowledge) less than 30k miles ago, by the PO. I just put some Delphi coils in their place. They made a noticeable difference, even with the 30k plugs and wires that they are currently firing through. Better throttle response, better low-end pull, just better in general. So, even without a plug or wire change yet, they made a noticeable difference. Why Delphi? They worked in my wife's BMW, and are approved as an updated coil in that car. Familiar name, perception of quality based on previous experience. They did look to be of fairly good quality.

On my other RX-8, when it was "running" with a186000 mile semi-blown engine (my guess was one apex seal chipped, since compression was suddenly lower across 2 chambers on the rear rotor.) Lumpy idle, looooonnnnnggg starts hot or cold, and hard to keep running at idle with a/c on. That's how I bought the car. As an experiment on that car at the time, I bought fresh plugs and a cheap $50 coil set from Amazon. I noticed an immediate difference again even with a sick engine. Faster starts, kept idle better, and more power, especially noticeable in top gear roll-on acceleration. Again, the coils that were replaced were rev C, of unknown mileage.

So, what have been the experiences of others with the rev C coils?

 

Mine is on the car like 21k km(so 13k miles) ago. So far no issues. I don't have a dyno, though.

There are also the NGK and Hitachi OE style coils. I think the improvement may just be from a new set of coils versus the brand.

 

I’ve had good success with the El Cheapo Intermotor Coils from Advance Auto Parts. @ $35 a coil + the typical 15% off discount code = cheap coil replacement that can be done every 20k miles so you are always running with fresh coils.

I dont even know why some of you think the expensive OEM coils are any better. They are all toast and running weak after 30k miles, so why waste money?