The stock, individual coil system on the RX-8 is very good and so far we have not found any advantage from changing it. We tested changes in timing for improved power but found no performance benefit! The fact is that Mazda has pushed the limit of ignition advance, and more (or less) timing advance yields no significant improvement.
We have also tested the knock sensor system and found that though it is good, it can cause minor problems. The sensor seems to detect normal engine vibrations as "knock" (pre-ignition), and because if this, the ECU retards the timing. Unbolting the knock sensor from the #2 rotor housing (do not disconnect it electronically - this will cause an ECU fault and retard the timing.) usually adds a small amount of power (often 1+HP) by eliminating the random, unnecessary retarding of ignition. Of course, if the engine should experience knock, your unbolted sensor will never know it- but cars ran for many years without these sensors and survived!
We have tested a variety of spark plugs in the RX-8 engine, and found that the stock plug is well-suited for this application. However, for racing applications, we recommend the NGK R6725-10.5 plug at .025"-.032" gap - they make additional power, but they are a very "cold" plug and will foul easily. These plugs can also be used in turbocharged applications.
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