Complete wetout of the dry fiber reinforcement by the liquid resin depends strongly on the fiber volume fraction and the resin viscosity of the part being manufactured by rein injection pultrusion. High fiber volume fractions and high resin viscosity values yield high pressures in the tapered resin injection chamber; this work investigates the use of a an injection chamber detached from the pultrusion die in order to lower the resin pressures inside the injection chamber caused by the injection chamber tapering. A 3D finite volume technique was developed to simulate the flow of resin through the glass rovings for a variety of resin viscosities and fiber volume fractions. The results illustrate the impact of the tapering of the injection chamber walls on the minimum injection pressure necessary to achieve complete fiber matrix wetout and the resin pressure induced inside the tapered injection chamber. The results provide important injection chamber design information.