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PI converter stall

5K views 31 replies 10 participants last post by  tbolt 
#1 ·
Those of you running a PI converter, what is your stall set at?
 
#4 ·
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.

From: Precision Industries - FAQ's


One thing I noticed is that the TC that BTS installed is either lower stall than stock (not likely), or much more efficient. It feels like the stall is lower simply because it pulls more at idle than the stock one did.
 
#5 ·
Might be a little backwards there. I don't know really, but this is my guess.

Lower stall on a Powerstroke will be more doggy, or slower just casually putting off idle around town, traffic lights, stop signs. Higher stall will let the RPMs raise, more power, more boost, more whatever and the truck will start to move a little later than the lower stall making it not as a "dog" since you're already up in some RPMs.

You obviously wouldn't want a 1,200RPM stall on a 600RWHP 7.3L.
 
#10 ·
Me? Yes i have a 6.0 cooler. I rebuilt my own trans and installed a pi converter and stall seems to be around 1000rpms, thats all i can get out of it. Trans works flawless. Just trying to narrow a few things down.
 
#12 ·
its right around 2000 on mine, at 2100 it starts tryin to pull through the brakes even hooked to the sled
 
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#20 ·
1600 is what BTS uses and I was told that's what DI orders as well.....

You want as tight as possible in most cases because there will be less of a difference between lockup and non lockup. When you hit second gear the "tighter" the converter, the less RPM drop you will see when you lockup the converter.

Now this excludes the guys running big singles that may need more stall speed to spool on the line, but the average guy with smaller turbos doesn't need more stall speed than the default 1600.
 
#32 ·
Stall speed is the rpm at which you get max power transfer through the fluid coupling. Stall speeds are adjusted with design to get the engine in the power band that you want to launch at. Tight = better economy Loose = harder launch & poor economy. A tight conv is better for towing and daily driving and a loose one better for racing and probably sledpulling. All this is dependent on the torque of the engine. A 3500 behind a small block will stall at a lower rpm than a big block. Someone already hit on this but this is the best explanation I can offer.
 
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