Having had to correct this type of issue on so many occasions we’ve been able to narrow down the primary causes.
The first thing that should be mentioned is a pinging, knocking or detonation sound (all of which are the same thing). This is essentially, unintentional fuel ignition inside of the combustion chambers and is, in short, usually caused by running the engine on fuel of too low an octane rating. You can normally get to the bottom of this by using a better quality fuel, such as Shell vPower Nitro+ (recommended by Rotary Revs) and seeing how this impacts your engine and driving experience. Many customers have reported positive benefits of changing their petrol of choice to that of a higher octane containing fuel in their feedback to us.
The second issue we see which makes a similar sound, is that of a failing Stationary Gear Bearing. Essentially the wear on the bearing allows excess movement of the E-shaft which causes the clattering sound. Ultimately this will result in complete engine failure and can only be cured by preempting the failure and replacing the bearings (or waiting for it to fail altogether and then stripping the engine down for a rebuild).
If you feel your car is showing or displaying any of the above symptoms, noises or sounds we cannot stress or recommend enough that you call us to discuss the problem with one of our RX-8 specialist mechanics as soon as possible.