For a variety of reasons, race engines can experience either or
both these conditions involving uncontrolled combustion. And, we
all know either or both can cause power losses and potentially
damaged parts, depending upon the frequency and severity of the
events. Experience has shown that there is sometimes a
misunderstanding about how these two events are created, what
actually takes place in the combustion space when they do occur,
and ways to avoid both problems. First, let’s examine each of
the events to determine how they transpire. During normal
combustion and following spark ignition, the flame front travels
through the combustion space, burning air/fuel charges while
compressing and raising the temperature in the remaining,
unburned air and fuel. Tests have shown that during this
process, the pressure in the burning and unburned charges are
relatively equal. If we focus our attention on what is occurring
with and within the remaining unburned air/fuel charge, we find
that as the flame front is approac