The historic use of leaded petrol and how it affected humanity
Marco Wong
Introduction
There was a problem in the automobile industry in the late 1910s. Rapid technological development meant that engines were in increasing need of power that fuel at the time could not provide. Engineers needed to find a fuel that was not only cheap but could easily be mass produced and could withstand higher pressures without undergoing spontaneous combustion, all the while being effective at a low concentration. Charles Kettering, head of research at General Motors (GM) at the time, delegated Thomas Midgeley Jr to invent an additive to petrol that could fulfil all the requirements, and the solution he came up with was tetraethyl lead (TEL). However, whilst TEL solved all the problems of the 1920s, it only managed to kick the can down the road, creating a whole slew of problems plaguing society throughout the 20 th century.
Engine knocking
In a 4-stroke engine typically used in automobiles, the fuel is compressed in the compression stroke and ignited with a spark plug and detonated during the power stroke.
Figure 1: The complete cycle of a 4 stroke engine 1
However, when high compression engines put the fuel/air mixture inside a cylinder under too much pressure, the fuel within may detonate prematurely and spontaneously combust. When premature combustion occurs inside an engine, it is no longer ignited by the spark plug at the beginning of the power stroke, thus being ‘ out of phase ’ causing a shockwave to be sent through the engine. This
1 Bikes Republic, accessed 4 th August 2023, http://www.bikesrepublic.com/wp- content/uploads/2018/01/4strokesengine.gif.
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