Many index and methods for knock intensity evaluation and knock onset determination have been proposed by means of in-cylinder pressure analysis.
Knock intensity, onset location and timing have been studied through a new methodology based on high temporal resolution optical diagnostics.
Figure 19 displays the dependency of knock intensity
on ethanol content.
Whilst discussing spark-ignition knock, Heywood  points out that due to the highly variable nature of engine knock, fundamental definitions of knock intensity
is extremely difficult to make.
The system also has the ability to compute, in real-time, additional individual cycle combustion parameters such: as IMEP, PMEP and NMEP; misfires; peak pressure, maximum rate of pressure rise and locations; polytropic coefficients of expansion and compression; upper, lower and average pressure envelopes; injector start and duration, both crank angle and time; mass burn fraction and rate; engine averages of IMEP, NMEP, peak pressure, maximum rate of pressure rise and their location; and knock intensity
Analyses were made of end-gas autoignition and its development process during engine knock operation at different levels of knock intensity
The faster the flame speed, the less the end gas involved in the knock combustion, and the weaker the knock intensity
Consistently with the theoretical expectations, the knock intensity
increases advancing the spark timing and reducing the water amount.
In both tests the compression ratio at a standard knock intensity
for the test fuel is compared to results for a set of primary reference fuels (PRFs).
5 CAD delay, as soon as the predicted knock intensity
overcome a certain threshold, fixed to 1.
Therefore, an empirical indicator has been devised to attempt to quantify knock intensity
by means of determining the pressure rise which may be caused due to the spontaneous ignition of the unburned charge using the relation,
The used methods, knock intensity
and number of pressure waves, do not show significant differences in knock behavior for the natural gas - gasoline blends compared to the gasoline type fuels.