== 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 simple view of double covalent bonds A double covalent bond is where two pairs of electrons are shared between the atoms rather than just one pair. Some simple molecules containing double bonds Oxygen, O2 Two oxygen atoms can both achieve stable structures by sharing two pairs of electrons as in the diagram.The double bond is shown conventionally by two lines joining the atoms. Each line represents one pair of shared electrons.ome simple molecules containing double bonds Oxygen, O2 Two oxygen atoms can both achieve stable structures by sharing two pairs of electrons as in the diagram. The double bond is shown conventionally by two lines joining the atoms.