The middle two cylinders were transformed into the expansion cylinder. To make the combustion cylinder exhaust ports and the expansion cylinder intake ports on the same side of the engine, the intake valve and exhaust valves should exchange their positions for the expansion cylinder compared with the original 4RB2 engine.However, because the cylinder cover body was not changed, the expansion cylinder intake valve were the same with the combustion cylinder exhaust valves, and the expansion cylinder exhaust were also the same with the combustion cylinder intake valves. The valve lifts of the expansion cylinders were also the same with the combustion cylinder, but the valve timing changed to รูป.4(b)ใ The combustion cylinder exhaust ports and the expansion cylinder intake ports were all connected by a connecting chamber, and the intake and exhaust manifolds were both on the other side of the engine. The combustion cylinders remained the same with the original engine.