The YSZ–TBC had higher (a) peak cylinder pressure at 2000 RPM and a correspondingly higher (b) rate of heat release due to advanced combustion phasing. Pintake = 104 kPa, 10.3 mg fuel/cycle, 90 °C Tintake, 95 °C Tcoolant, Toil, 20.9–21.1 AFR, 47.7–48.9% RGF, 0% external EGR.