This paper presents a new concept of the controllable premixed combustion (CPC) for an internal combustion engine fueled with dimethyl ether (DME). The CPC system is composed of an electronic control low pressure injection system, a premix chamber and a main chamber. Between the two chambers, a control valve is set. DME is entirely injected into the premix chamber at the end of the intake stroke after the control valve closed. Then, a homogeneous mixture is formed with the residual gas of the last cycle in the premix chamber. Ignition takes place in the premix chamber after the control valve was opened before TDC, and then, the high pressure and high temperature gas rushes into the main combustion chamber. A test bench was constructed based on a single Diesel engine, and the electronic control low pressure injection system was developed. Preliminary studies demonstrated that ultra-low NO, emissions had been realized without smoke emission. NO, emissions are less than one tenth of those of the base direct injection Diesel engine fueled with DME. (C) 2003 Elsevier Ltd. All rights reserved.