RESTRICTORPLATE
Restrictor plate
A restrictor plate or air restrictor is a device installed at the intake of an engine to limit its power. This kind of system is occasionally used in road vehicles for insurance purposes, but mainly in automobile racing, to limit top speed and thus increase safety, to provide equal level of competition, and to lower costs; insurance purposes have also factored in for motorsports.The above text is a snippet from Wikipedia: Restrictor plate
and as such is available under the Creative Commons Attribution/Share-Alike License.