Many an auto owner has been vexed by engine knock. Now, researchers at the University of Southern California have discovered the chemical basis for this rat-a-tat--and they hope to vanquish it.
USC chemistry professor Sidney W. Benson found that hydrogen peroxide forms during combustion of gasoline and air. As the gas-air mixture in an engine cylinder heats up, the hydrogen peroxide breaks down into a hydroxyl group--a combination of hydrogen and oxygen--which reacts with gasoline and ultimately causes a rapid, premature burning of the fuel. The resulting small explosions cause the "ping" of engine knock. Benson and fellow researchers also found that lead controls knock by preventing hydrogen peroxide from forming.
Adding environmentally toxic lead back to gasoline isn't an option. And other knock-inhibiting additives are both expensive and polluting. So, Benson is now looking for a knockbuster that won't foul the air.