Camshaft modification for conversion of four-stroke engines to six-stroke engines

In this study, camshaft modification was carried out to convert a four-stroke engine into a six-stroke engine. For this purpose, six-stroke engine strategies in the literature were examined in detail. As a result of the examination, a free-stroke strategy without exhaust heat recovery was preferred. In order to carry out engine experiments, a power generator using this engine was provided. For the conversion to a six-stroke engine, first the original camshaft dimensions of the engine used in the experiments were determined. Cam profiles were designed for a six-stroke engine by defining the measured cam profiles within a certain mathematical model. Since the experimental engine has a flat faced follower, a double arc cam model was used in the design of the cam profiles. The camshaft is basically designed in three basic parts. Since there are many sensitive parts in the production of the cam gear, it was produced using PAHT CF filament using 3D printer technology and then the assembly was completed using miniature bearings and steel shafts. The cam lobes are cut and hardened from 4140 tempered steel using the wire erosion method. M12 standard thread screw shaft was used to combine the cam lobes and cam gear and to make angular adjustment of the cam lobes. The experiments were carried out on a monophase power generator with a rated power of 5 kVA. A resistive load cell with a power of 4000 W was created to load the generator. Fuel consumption, oil temperature and exhaust temperature were measured in the generator, to which electrical load was applied at 400 W intervals, and thermal efficiency and specific fuel consumption were calculated. As a result of the experimental study, a 13.4% improvement in fuel consumption was observed. Additionally, thermal efficiency is increased by 15.8%. This study experimentally demonstrated that four-stroke engines could be converted to six-stroke engines, and that such a conversion could achieve fuel economy at the expense of power. This suggests that six-stroke engines could serve as an alternative to Atkinson cycle engines currently used in hybrid electric vehicles.