Pinging, knocking or detonation are terms for a rattling sound that emanates from the engine when under load and sounds like nuts/bolts rattling around in a hubcap. It is the sound of destructive, abnormal combustion and severely shocks the conrods, pistons and crankshaft. You may or may not be able to hear the noise, which means that damage can occur to your engine without you knowing about it. Detonation is another name for pinging. Higher octane fuels and quality tuning is required to keep pinging under control. Click here to view a report from Metallurgical Testing & Consulting Engineers in relation to a customer's engine failure.