Outwater base and engine bracket for Nissan car were manufactured by using double-directional convergent runner. It is found that the gas-pore defects present in the die castings

and the permeability rate is more than 90%. The easily presented position of the defects was observed by computer simulation. The above problems can be eliminated by thickening ingate

setting two overflow slots

increasing the diameters of stationary mould core and adjusting processing parameters.