Redline

The maximum recommended engine speed (measured in revolutions per minute ) at which an engine is designed to operate without causing damage to the components or other parts of the engine.

The redline is determined by the manufacturer through stress-testing, and can vary from a few thousand revolutions per minute (in large engines) to nearly ten thousand rpm in smaller, usually high-performance engines such as sports cars with rotary engines.

Petrol engines have a typical redline at around 5.600 - 6,500 rpm, although the Renesis engine in the Mazda RX-8 has a redline of 9,000 RPM. In general, diesel engines have lower redlines than comparatively-sized petrol engines.

The redline is usually indicated by a red line or coloured sector marked on the vehicle's tachometer. Although straying into this area usually does not mean instant engine failure, it can increase the chances of damaging the engine. However, the majority of modern cars prevent the engine from straying too far into the redline by disabling the ignition system until the engine drops to a safer operating speed or by cutting fuel flow to the fuel injectors or carburettor.

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