Torque Converter

(2) Four element torque converter
(a) The four element torque converter contains a driving member, or impeller, a driven member or turbine, plus a primary stator and a secondary stator. Each of these stators is mounted on an overrunning type clutch shown in Figure 17. When the torque converter is first started, the impeller is rotation much faster than the turbine. The two stators are held stationary and they redirect the oil as it leaves the turbine. This is shown by the arrows in Figure 18. In other words, as the oil comes off the turbine vanes, it strikes the stationary stator vanes and has its direction changed. This enables I to enter the impeller in a direction that does not hinder the impeller rotation.
(b) The turbine speed increases until it nears the speed of the impeller. The oil leaving the turbine vanes gradually changes direction until it begins to strike the back faces of the primary stator vanes. This will cause the primary stator to begin to rotate. The secondary stator still is stationary and will continue to change the direction of oil.
(c) When the speed of the turbine is near equal to that of the impeller the oil will now strike the back of the secondary stator vanes. Now the secondary stator also begins to rotate. Neither stator enters into the action now, and the converter acts as a fluid coupling.
(3) Five element torque converter
(a) The five element torque converter is similar to the four element converter, the main difference is the addition of a secondary impeller. The secondary impeller is not used during heavy load or hard acceleration operation. It is mounted on an overrunning clutch (Figure 17) which allows it to spin faster than the primary impeller, however, the secondary impeller locks when it attempts to rotate slower than the primary impeller. This locking forces both impellers to turn at the same speed.
(b) The force that causes the secondary impeller to spin faster than the primary impeller comes from the oil striking the back faces of its vanes.
h. Torque Multiplication Factors
Since torque converters vary considerably in design, the amount of torque multiplication they can achieve also varies with the practical limit being 5:1. The torque multiplications would normally depend on the size of the converter, the number of elements and the piece of equipment the torque converter was designed for.