Engines combustion is designed to occur as a propagating flame front in the cylinder initiated by the spark plug. Great efforts are made to ensure that this is

Engines combustion is designed to occur as a propagating flame front in the cylinder initiated by the spark plug. Great efforts are made to ensure that this is precisely what happens. The alternative is a detonation, i.e. engine knocking. This causes a spike in cylinder pressure and will quickly destroy an engine. It is for this reason that engines are absolutely not trying to burn fuel as quickly as possible. This is a difference of detonation vs. deflagration. Whether you consider both of these to be forms of explosions is a semantic issue.