== 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).
covalent bond, a chemical bond that forms by the sharing of two electrons between atoms. A double bond is formed when four electrons are shared between two atoms; a triple bond is formed when six electrons are shared between two atoms. chemical bond that involves sharing of electrons between atoms of the same element to give a molecule of that element (e.g., nitrogen) or atoms of two or more elements to give a molecule of a compound (e.g., carbon dioxide); the predominant type of bonding in organic chemistry.