1. The burning gases can ignite the lean mixture.

2. Suprastoichiometric combustion, i.e. using a fuel-lean mixture to dilute combustion heat;

3. The Achates OPGCI injects fuel early in the compression cycle for a lean mixture, with incoming air and residual exhaust that is purposefully left in the cylinder

4. On the other hand, the fuel consumption of the quasi-homogenous mixture lean combustion decreased by about 5% compared with homogenous lean mixture combustion during all the A/F.