Thanks to HAJI, the rate of combustion is still very fast
running ultra-lean V¼ 0.43. As soon as the fuel-to-air
equivalence ratio further reduces, the speed of combustion
reduces as well as the energy available for pressure build up.
The crank angle for peak pressure can be kept to values
about 15–20 crank angle after top dead center with
V¼ 0.43–0.28. With V¼ 0.43, peak pressure may exceed
120 bar. When the fuel-to-air equivalence ratio drops to
V¼ 0.18–0.21, either the combustion rate is not fast enough
and the energy available is not large enough to build up
a proper pressure profile, and the peak pressure is shifted
towards top dead center. Peak pressures may drop up to
40 bar with V¼ 0.18.