Gasoline engine knock

Antiknocks. Antiknock agents are used to improve the natural knock resistance of gasolines used in Otto-cycle gasoline engines, knock being the power-robbing, po-... 

D. Bradley, Hot Spots and Gasoline Engine Knock, J. Chem. Soc., Faraday Trans. 92 (1996) 2959. 

Product characterization aims at defining their end-use properties by means of conventional standard measurements related as well as possible — and in any case, being the object of a large consensus— to end-use properties. We cite for example that octane numbers are supposed to represent the resistance of gasoline to knocking in ignition engines. 

Uses Standard in testing knock of gasoline engines and for octane rating determinations anesthetic solvent organic synthesis. 

Source Some unleaded gasoline may contain isopropyl ether and other oxygenates as an octane booster and to prevent engine knock. 

In the past, tetraethyl lead was added to gasoline to slow its burning rate in order to prevent engine knock and increase performance. This caused serious and harmful pollution, and lead has since been eliminated as a gasoline additive in most countries. Most exterior (and some interior) house paints once contained high levels of lead as well. Today, the amount of lead in paint is controlled, with not more than 0.05% allowed in the paint material. 

It is known that a small amount of lead tetraethyl is effective as an anti-knock agent in gasoline engines. This effect is due to the inhibition of the gas-phase reaction by the lead or lead oxide derived from the lead tetraethyl.l o.si] The inhibitory action of lead compounds on hydrocarbon combustion is largely exerted in the gaseous phase of the combustion zone. 

Problems related to engine knock can be readily diagnosed by measuring the octane number of gasoline. However, it is also possible to look at the distillation profile of gasoline and anticipate problems linked to engine knock. 

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