Automobile Wankel rotary engines are capable of high-speed operation. However, it was shown that an early opening of the intake port, longer intake ducts, and a greater rotor eccentricity can increase torque at lower rpm. The shape and positioning of the recess in the rotor, which forms most of the combustion chamber, influences emissions and fuel economy. The results in terms of fuel economy and exhaust emissions varies depending on the shape of the combustion recess which is determined by the placement of spark plugs per chamber of an individual engine.