[Tervuren]

One more attempt in case that doesn't stick.

In the conventional engine the spark creates a higher temperature as the source of ignition, heat radiation is how the reaction spreads through the combustion chamber.

In this Mazda engine a small reaction in the combustion chamber creates an increase in pressure, and compression is how the remaining fuel/air mixture burns.

So in the conventional engine it is heat radiation for ignition at a given compression.

In this Mazda engine it is heat radiation with a small part of the chamber in fuel air mixture ratio 1 that is ignited. This combustion expansion changes the compression ratio for fuel air ratio 2 that fills the remaining area of the chamber. This change in compression ignites fuel air ratio 2.

So the part of the chamber at fuel air 1 ignites by heat at compression level A, the part of the chamber at fuel air 2 ignites by increased compression to compression level B.

The compression ratio for ignition of fuel air 2 is higher than that of fuel air 1.

Fuel air mixture 1's combustion is used to control the compression of fuel air mixture 2.

If you spray food coloring into water, there is time for it to dissipate to median levels.
The second injection of fuel does not have time to mix with the remaining part of the chamber.
This results in two different fuel/air ratios in the chamber at the same time, one of which is used to raise the compression of the other.