What is the stall on the Torque Converter?

[cyled]

Wednesday night in the Chat session we where discussing the stall of the torque converter. Two numbers came up 2500 and 3500. I believe it is around 3500 just by the way the car acts at 1/2 to 3/4 throttle.
When you hit around 3000 -3500 it doesn't have that "slipping" feeling. I know it is not actually slipping, it is actually doing its job by not applying all of the torque, hence the name torque converter...

Just curious what the brochure means when it says "a high-stall-speed torque converter". Plus just for doing future mods it would be nice to know.

[LincMercLover]

That's not how you measure the stall speed...

[Billatpro]

Then how do you measure it?

[LincMercLover]

Dead stop (perferably no cops in sight), punch it, WOT. The RPM's will jump real quick, then slowly climb as the car accelerates. Where the needle starts it's SLOW climb is where the stall is. I think it was said to be about 2500-2700RPM.

[joflewbyu2]

2550-3011 rpm according to the computer based on several variables such as load, throttle position and so on.

[mensrea]

From PrecisionINdustries LET ME SAY IT AGAIN - YOU NEED TO BUY THIS CONVERTER, OVER 25 HORSE AT THE REAR WHEEL, AND AN INCREASE IN GAS MILEAGE. BUY IT, INSTALL IT, LOVE IT,

Frequently Asked Questions:

HOW CAN I DETERMINE THE STALL SPEED OF MY CONVERTER?
Stall speed is very difficult to determine unless your car is equipped with a Transbrake to lock your drive train. Testing stall speed by holding the wheel brakes and running the engine against the locked brakes will usually result in wheel rotation before true stall speed is reached. The engine simply overpowers the ability of the brakes to hold the car. When rotation starts you are no longer at stall. For this reason people talk about brake stall which is not a true stall at all. An alternative method of measurement is to launch at wide open throttle and observe engine RPM reached at launch. This is flash stall.

WHAT ARE FLASH STALL, BRAKE STALL AND TRUE STALL?
The truest definition of stall speed can only reliably be determined in conjunction with a Transbrake. Wheel brake stall is determined by locking wheel brakes and running the engine against the locked brakes. As discussed above, the engine will usually overpower the brakes and wheel rotation will begin before the true stall speed is encountered. Flash stall is observed by launch at full throttle and observation of peak RPM at launch.

STALL SPEED
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.

[TAF]

on this converter. Is this installed in your vehicle? I'm interested in looking at this, tell me where...

[Billatpro]

Good info Mensrea,
To expand on that a little and answer the the gear vs the stall question: The only real advantage of a high stall converter is at the launch, where the "flash" stall allows you to put the engine higher into it's torque/power band and thus provide more "grunt" at the line. once underway most if not all advantage is gone, lost to inefficiency, heat build and slippage. This is why a "stick shift" car will out perform an Automatic car.

as for the 4:10 gear comp over the high stall converter, the 4:10 gear will provide benifit for the full tour of the 1/4 mile due to the fact that not only will the gear multiply engine out put at the launce but at all intervals down the track, while holding the engine higher in the torque and power band.

[RF Overlord]

Originally posted by Billatpro

To expand on that a little and answer the the gear vs the stall question: The only real advantage of a high stall converter is at the launch, where the "flash" stall allows you to put the engine higher into it's torque/power band and thus provide more "grunt" at the line. once underway most if not all advantage is gone, lost to inefficiency, heat build and slippage.

I think you said it all right there, Billatpro...

I've driven cars (not mine) with very high stall-speed converters on the street, and once the initial novelty wears off, they're no fun...especially when trying to accelerate from a stop light with a cop car right behind you...! Vroooom! Screeeech! "License and registration, please"

[mensrea]

I beg to differ.... the 3000 converter in my car does not slam at all, is not harsh, you don't even notice its there. And there is a noticeable increase in gas mileage with no other mod. The converter is much more efficient than the stock one. Remeber you can program the converter to lock up at WOT.

This thing added almost 30 horse to the rear wheels, I think that says a lot about its efficiency.

[SergntMac]

Mensrea, how about a part number on that Torque converter, web site's not clear on some points. Did you need to change out anything else but the TC at install? Did you have to get inside the tranny at all? Do you think it would perform to the same degree with a N/A MM?

If I can buy 20 or so RW HP and likewise torque for 750., who do I call?

Thanks for the info.

[mensrea]

I would suggest that you give them a call directly, they are really nice people... I met them at PRI this year. I know they build each one custom for the app, so you will hae to talk to them and figure out what specs you want, kind of like ordering DynoTech's driveshaft The one that fits ours is the stallion.

The converter will work as well on a NA car, it is that much more efficient than the stock one.

You may need to ask them if you need to reprogram your chip to controll WOT lockup, or if that is something that they can do with the converter.

Another neat thing about them is that if you want the converter modified, lower stall, etc there is no charge for the mod after you buy it,.,, kinda cool.

[Billatpro]

Mensrea, with regards to the results you experienced, I have no doubt you are totally right on and it is a resonable result, considering the fact that the converter can be programed. My statements were directed at the drag strip senario. Most drag cars do not have the ability to program stall at WOT or anywhere else for that matter. this capability would produce a converter for the best of both worlds. The question was I believe, "results at the drags" and there is more then enough information that shows a 6:14 will out "result" a 5000 stall converter, hands down.

[cyclone03]

Billatpro,
My fault for spliting this thread.
You bring up a good point.
If we optimized the rear gear for drag only I'm sure we would only use the first 3 gears no OD.
Then we would "tune" the launch with the converter,exit RPM with the rear gear.Thats how/why the auto stock elm. cars cars run so well.Lots of gear and converter.
It was mentioned about useing the FMS converter in the 5.0 stangs,that is not the same trans as our 4w70.(well it sorta is)In the old AOD 3rd gear locked up with no torque multiplication from the converter,thats what that little shaft was for in the trans.Our trans locks up the clutch in the converter.It allows the converter to,well,convert in 1st,2nd,and 3rd. and also in OD too. It also locks up in all but 1rst too.I think,I'm still trying to get an answer on that one.
My point in the other thread was,and still is,with one change which would ET better?
I know the answer is TEST,TEST, TEST.

[SergntMac]

It's confusing to have 2.5 threads running on basically the same questions and answers, but at least we're all still in the garage.