mel3535

Can someone explain to me what a stall converter is and how it works?

alxltd1

Here you go:
If you've read about manual transmissions, you know that an engine is connected to a transmission by way of a clutch. Without this connection, a car would not be able to come to a complete stop without killing the engine. But cars with an automatic transmission have no clutch that disconnects the transmission from the engine. Instead, they use an amazing device called a torque converter. It may not look like much, but there are some very interesting things going on inside.

Stall converter is just like a plain torque converter. it is somewhat of a clutch that controls the automatic transmission. A Stall on the converter does exactly what it says, it stalls (actually I believe it is more of a controlled slippage) the converter to only work above a certain rpm. Example a 1500rpm stall converter will not transmit torque to your transmission untill you get past 1500rpms, thus you start at a higer rpm boosting your speed. Just like someone in a stick launching at higher rpms.

No expert so others will chime in I am sure, but this should give you the basics.


The Basics
Just like manual transmission cars, cars with automatic transmissions need a way to let the engine turn while the wheels and gears in the transmission come to a stop. Manual transmission cars use a clutch, which completely disconnects the engine from the transmission. Automatic transmission cars use a torque converter.


A torque converter is a type of fluid coupling, which allows the engine to spin somewhat independently of the transmission. If the engine is turning slowly, such as when the car is idling at a stoplight, the amount of torque passed through the torque converter is very small, so keeping the car still requires only a light pressure on the brake pedal.

If you were to step on the gas pedal while the car is stopped, you would have to press harder on the brake to keep the car from moving. This is because when you step on the gas, the engine speeds up and pumps more fluid into the torque converter, causing more torque to be transmitted to the wheels.
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mel3535

ok so what kind of stall converter do they have, like what is a difference between a 3600 stall converter and 1600 or something like that, how does it effect day to day driving if you have a high stall converter ?

alxltd1

check the edit I just put in.

Exoray

One engages the tranny at 1600 rpms the other engages the tranny at 3600 rpms, for day to day driving you will find that the higher number make for a much less enjoyable ride in traffic or stop and go... That is unless you like the jump off the line experience everytime...

mel3535

so what kind of stall converter does a stock car have? a very low number i am going to guess

madmatt9471

Dude definetely not a stupid question at all!

Here is YANK Converters (Which I use) Frequently Asked Questions Page. take a look at it and it will help tremendoustly:
http://www.converter.cc/faq/

Believe me you will love having a stall converter in your Vette, it will not mess up daily driving at all - I have a 3200 stall in mine and it drives normal, but when the hammer is smashed it flashes up into the RPM range and launches

Of course this works the best with my slicks on

You can call YANK and talk to Dave he will answer any and all questions you have! You can also give me a ring if you'd like too 661-406-7516

Thanks,Matt

dobewillie

Good post thanks all

Choreo

I believe it is something that changes your barn into a garage?

Silverbullet00

Now that's funny right there, I don't care who you are!








p.s. Not exactly an original line!

95wht6spd

I have never had an auto on any car, this is what I have always wondered, since even at idle they will move forward on a stock car, even if you have a 3600, you will start moving off idle right? I mean it just will really kick in a lot more at 3600 right?

FrankTank

The higher the stall (3600, 3800 etc etc) the more "kick" or jolt you are going to get... the number refers to the engine RPM that the Tranny engages at, as stated in a couple posts above.

Maybe a bad example, but think of a stick shift car, and reving the engine to 3600RPM, and dumping the clutch..what happens In theory this is what a stall is doing...ist a bit different with an auto but again.. the number of the stall refers to engine RPM , and when the tranny fully engages.

mel3535

so if it get a 3600 my car does not move until i hit 3600 RPM?

damilleniumboy

damn, interesting post.

alxltd1

These are not my words but may help:

A torque converter is the direct connection between the engine and transmission. It works much the same way that a stall converter works, but to understand a stall converter, you must first understand how a torque converter works. The torque converter is attached to the flexplate by three bolts and the transmission input shaft slides into the torque converter. It meshes into the converter by a set of splines on the male end of the input shaft and into a hole with splines in the torque converter.
The torque converter has four major components. The first component is the impeller or pump, which is directly attached to the converter. The pump is turning continuously. This produces the hydraulic pressure. The turbine is the next component and is not attached to the converter. It is free floating and attached only to the splined input shaft from the transmission. Its purpose is to supply the torque to move the vehicle. The next is the one way clutch that locks up the converter to the input shaft. The last component is the stator. The stator is designed to multiply the torque or pressure and reduce the speed of the impeller.
The best way to explain the operation is to imagine having two fans facing each other. Turn on just one fan and soon the second fan will begin to spin. If the second fan is held from moving, the first fan that is turned on will of course continue to spin. This is how a car can come to a stop and not stall the engine. Now add a stator in between the two fans. Turn the working fan down to low. The driven fan or the one that is not turned on will have much more pressure although it can still be held. This is similar to an idle or the car sitting still.
Turn the working fan on high, which is similar to stepping on the gas. The driven fan comes to life and can no longer be held. This is basic, but it best explains the way the converter works. The rpm that the torque converter begins to apply torque is dependent on the curvature and type of blades used on the stator and impeller. The normal efficiency of the torque converter is 90 percent of engine speed, hence the lock up clutch. The other 10 percent allows the engine a little flash time for accelerating without lugging the engine. For fuel economy, the lock up will only occur electronically at a cruise or 50 miles per hour and up to a point where no further torque is required. This makes 100 percent 1:1 ratio that lowers the engine rpm and saves fuel.
A stall converter does what a torque converter does, but has a modified stator that requires a higher than normal rpm before it locks up. Lock up is determined by the amount of rpm the engine can achieve with the brakes on. Stall converters can be purchased with a wide range of stall from 1200 rpm to 6000 rpm. Ideally for the best launch or acceleration, the stall should be 80 percent of the rpm necessary for maximum torque. Stall converters are generally used in racing applications or towing applications, but it is not unheard of for a high horsepower street vehicle to be equipped with a stall converter instead of a torque converter.

Every converter has a stall speed and this is the rpm at which the engine will stall against the transmission. If you have ever driven an automatic tranny you have experienced what happens with a converter at idle. If your stock converter has a 1500 rpm stall speed, you don't need to rev it to 1500 rpm to get the car to move, it will creep at idle. If you were to increase the torque of your engine and raise the stall speed of your stock converter to 2500 rpm, it would act the same as it always did, except you could rev the engine to 2500 rpm against the converter before it would stall.

A lockup converter will lock up any time you engage the lockup clutch.

mel3535

ok so my stock 05 coupe right now has a torque converter?

i still am kind of confused, So if i have a 3600 do i need to rev up to 3600 for me to move or can i still drive even if i don't get to 3600 rpm?

alxltd1

Every converter has a stall speed and this is the rpm at which the engine will stall against the transmission. If you have ever driven an automatic tranny you have experienced what happens with a converter at idle. If your stock converter has a 1500 rpm stall speed, you don't need to rev it to 1500 rpm to get the car to move, it will creep at idle. If you were to increase the torque of your engine and raise the stall speed of your stock converter to 2500 rpm, it would act the same as it always did, except you could rev the engine to 2500 rpm against the converter before it would stall.

Exoray

More so like you are riding/feathering the clutch and when you hit 3600 rpm you suddenly release it... The car will still go forward at the lower RPMs but the tranny won't be fully engaged... The stall in essense takes most of the load of the engine so it can spool up to the higher RPM without a fight, then it unleashes...

Example at a stop light, foot on the brake apply gas but keep your foot on the brake lightly, you won't get much fight from the car to move forward (not saying it won't give any fight, it will just be minimal) even with the light brake peddle you will be able to remain still, that is until and the engine RPMs hit the stall number, at that point the tranny will engage solid and you are off to the races...

mel3535

so if it dont put my foot on the break and just give it gas it will just drive like normal, but if i touch the break i can launch it at that RPM like a manual car?

alxltd1

Just to add to the above. A stall converter is a viscous coupling that you could compare to a clutch as far as what it's function is. As the engine rpms come up, it allows less and less slippage until it reaches full lockup at the stall speed - at that point it's like having the clutch all the way out. All automatics have and need them because otherwise you could never get the car going from a stop. The idea behind having a higher rpm stall converter is the same as slipping the clutch off the line to get a better launch - keeps the engine from bogging and allows it to get into the powerband quicker. You just wouldn't want too high of a stall on a street car because if you are trying to cruise with the rpms below full lockup then it is always slipping and you are wasting gas and power and generating excess heat.