== EGR vacuum switching valve == Despite the rather lengthy name the EGR-VSV (exhaust gas recirculation vacuum switching valve) does little more than allow vacuum to flow through the system depending on engine coolant temperature.
A double bond in chemistry is a chemical bond between two chemical elements involving four bonding electrons instead of the usual two. The most common double bond, that is between two carbon atoms, can be found in alkenes. Many types of double bonds exist between two different elements. For example, in a carbonyl group with a carbon atom and an oxygen atom. Other common double bonds are found in azo compounds (N=N), imines (C=N) and sulfoxides (S=O).
a type of chemical bond involving the sharing of electrons between atoms in a molecule, esp the sharing of a pair of electrons by two adjacent atoms. covalent bond in Medicine Expand. covalent bond n. A chemical bond formed by the sharing of one or more electrons, especially pairs of electrons, between atoms. covalent bond. A chemical bond formed when electrons are shared between two atoms. Usually each atom contributes one electron to form a pair of electrons that are shared by both atoms. See more at coordinate bond, double bond, polar bond.