Isobutanol was injected with the intake port at premixed energy ratios (PER) of 10%, 20% and 30%. Diesel, B20 and B100 are direct injection fuel. DFC reduces nitrogen oxide (NOx) emissions at moderate loads compared to CCM. Compared with CCM, the flue gas emissions of diesel DFC under rated load are reduced by 10.15%, 22.12% and 7.40%, respectively. At 30% PER, the exergy efficiency of the D FC for B20 increases by 0.91, 5.23, 3.65, 1.22, and 6.14% from 20% to 100% load, respectively.