Re: Torque converter questions
Precision Industries - FAQ's
Torque converter stall is a commonly used term and is commonly misunderstood. Stall is the speed at which the converter will hold the engine speed and not allow further gain (i.e., the engine "stalls"). The key word here is engine. The speed at which stall occurs with a given converter is a function of engine peak torque. It is clear that the stall speed on a given converter will not be the same coupled to a tame small block engine when compared to a big block with all of the muscle features added. When comparing stall speeds it is important to account for the engine that drives it. True converter stall can best be determined when a Transbrake is used. Testing for stall value by locking the wheel brakes generally does not produce a true stall value because the engine power can often cause wheel turn by overpowering the brakes. Stall speed determined by this method should be identified as such when discussing stall speed determination. Flash stall is determined by launching at full throttle and observing the peak speed attained at launch. Selection of the right stall speed for your vehicle should be matched to the engine peak torque, engine torque curve shape and vehicle weight. In general, the stall speed selected for your converter would be 500 to 700 rpm below the peak torque. This speed allows the margin for application of the torque reserve on takeoff. When selecting stall speed without having prior experience to go by, it is better to conservatively estimate the engine torque than it is to over estimate it. If you over estimate the torque output you will have a converter with a stall speed too low, making your car slow off the line and have slow ET. A properly selected stall speed will give you better launch and better ET. You can see why it is important to consult with professionals prior to making a stall speed selection. Within the converter, stall speed is balanced off against inefficiency after launch. Getting desired stall at the expense of performance after launch is just as costly as improper stall speed to begin. The optimum converter has careful selection and design of changes to the impeller, turbine and stator.
01 Excursion 7.3L Powerstroke. Gauges with AIH Delete, AIS, CCV Mod, 4' MBRP, BTS Trans, 6.0L Trans Cooler and Intercooler, DP-Tuner F5 chip, ITP In Tank Mod and Boost Annihilator, Diesel Innovation's Regulated Fuel kit, BTS Big Oil system, GTP38R Turbo with 1.15 A/R housing and BPD Stage II AC injectors. Bilstein Shocks with U front and A Rear.