In this study, port premixed methanol compression ignition combustion was performed on a heavy-duty diesel engine. The effects of methanol to diesel ratio (R-MD) and DIT (diesel injection timing) on combustion, performance and emissions were comprehensively investigated. The experimental results demonstrated that R-MD and DIT played important roles in combustion and emission control. With the increasing R-MD, the ignition delay was prolonged and the combustion duration was shortened. And as DIT retarded, the ignition delay was also prolonged and the combustion duration basically remained unchanged at the beginning, and then followed by a slight decrease. The maximum in-cylinder mean temperature decreased with the retarding DIT and it was largely affected by the combine of R-MD and DIT. The brake thermal efficiency remained stable at low R-MD, but showed a slight decrease at high R-MD, NOx and soot emissions and the RI (ringing intensity) were all decreased as RMD increase, while HC and CO emissions increased significantly. With the retarding DIT, HC emission firstly increased and then decreased, while CO emission always increased. It was more important that the trade-off relationship between NOx and soot was significantly improved with the increasing R-MD and almost disappeared at R-MD 1.54. (C) 2015 Elsevier Ltd. All rights reserved.