Rev limiter

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A Rev limiter is a device fitted to an internal combustion engine to restrict its maximum rotational speed. This is usually carried out to prevent damage to the engine, however sometimes these devices are fitted to prevent an engine reaching the point at which it develops maximum power. This may be useful in a driving school car or similar, or utilised in systems preventing Valet parking operatives from joy-riding in high performance vehicles placed in their charge. When fitted to racing or modified street cars these adjustable devices provide more precise control than the original components built in by the manufacturer. Limiters can be used in conjunction with a shift light, which illuminates when the desired RPM is reached, indicating to the driver that a gear change is required. This allows the driver to keep his eye on the road and not have to glance repeatedly at the tachometer to monitor the engine speed.

Limiters prevent damage to an engine by interrupting the power that is distributed to the spark plugs, this prevents the engine from operating above a pre-determined RPM level known as the red-line. The RPM level that results with the spark being arrested can be a constant level, or, with the proper ignition control modules, variable. Variable rate ignition modules can be adjusted quickly and easily to achieve the appropriate RPM limit for different situations, such as street racing, drag racing, road course racing, highway driving, and lawn turfing.

Multiple stage ignition modules offer greater RPM limit control. The first stage can be used to limit RPM levels when launching a vehicle from a stationary position, providing maximum power and traction. The second stage is activated after launch to set a higher RPM limit for wide-open-throttle acceleration.

Limiters are used as a means of increasing the fuel efficiency of commercial motor vehicles. Limiters can be individually adjusted by fleet owners to meet the performance requirements of many different driving conditions. Adjustments to limiter specifications can be achieved by mechanical or electronic means. Mechanical adjustments can be performed at any time by drivers of vehicles, with the use of simple hand tools. Electronic adjustments require special diagnostic equipment to access control settings, and are limited to authorized personnel, such as a fleet manager or mechanic.

Limiters are manufactured by numerous companies and are available for most vehicle and engine combinations.