valve cut-out

Definition

Cars & Driving

  • noun on some four-valve engines at low speed the main rocker arms open only two valves per combustion chamber in order to keep the energy of the gases at a high level; with increasing rpm, the energy of the gases becomes sufficiently strong for the remaining two valves to be opened via hydraulic locking bolts
http://www.dictionarycentral.com/definition/valve-cut-out.html