How Does a Rev Limter Work?
Many cars these days incorporate a device called a rev limiter to limit how fast the engine is able to go. This is usually a safety device meant to keep the engine from tearing itself apart by spinning too fast. However, it can also be used to limit the top speed of the vehicle. In most newer cars, rev limitation is a function of the engine control unit. When engine RPM or vehicle speed reach a preset threshold, the computer begins to interrupt the electrical signal to the ignition coil, limiting the number of times the coil can fire. Thus, slowing the engine down.
For more info, see How VTEC Works