I've always driven manual's. I really have no clue how it works. I understand it makes you take off quicker but that's about the extent of my knowledge on that. :) What are the drawbacks? How does it affect idle?

 

How the Converter Works



Automatic Hydraulic Clutch
In Reverse, low and second gears, the converter operates in hydraulic or soft drive conditions. In hydraulic drive, the converter functions as an automatic clutch (when the car is stopped) and as a torque multiplier (when engine load requires more torque).

The engine drives the impeller mechanically.
The turbine is driven hydraulically by the impeller.
The turbine drives the tube input shaft for input to the gear train.
Impeller Pumps Fluid
The purpose of the impeller is to put the fluid in motion. Inside the impeller housing many curved vanes, along with an inner ring, form passages for the fluid to flow through. The rotating impeller acts as a centrifugal pump. Fluid is supplied by the hydraulic control system and flows into the passages between the vanes . When the impeller turns, the vanes accelerate the fluid and centrifugal force pushes the fluid outward so that it is discharged from openings around the inner ring . The curvature of the impeller vanes directs the fluid toward the turbine, and in the same direction as impeller rotation

Rotary Force on the Turbine
As shown in View B (above), the turbine vanes in the turbine are curved opposite to the impeller. The impact of the moving fluid on the turbine vanes exerts a force that tends to turn the turbine in the same direction as the impeller rotation. When this force creates a great enough torque on the transmission turbine output shaft to overcome the resistance of motion, the turbine begins to rotate.

Now the impeller and turbine are acting as a simple fluid coupling, but we have no torque multiplication yet. To get torque multiplication, we must return the fluid from the turbine to the impeller and accelerate the fluid again to increase its force on the turbine.

Vanes Reverse the Flow
To get maximum force on the turbine vanes when the moving fluid strikes them, the vanes are curved to reverse the direction of flow . Less force would be obtained if the turbine deflected the fluid instead of reversing it. At any stall condition, with the transmission in gear and the engine running but the turbine standing still, the fluid is reversed by the turbine vanes and pointed back to the impeller. Without the stator, any momentum left in the fluid after it leaves the turbine would resist the rotation of the impeller.

At this point, we have a simple fluid coupling that will cause the turbine to drive the input shaft with no torque multiplication. To gain multiplication, we must add the reaction member or stator.

Enjoy!!!
:cheers:

 

why do you have samual l jackson from the great white hype in your sig?

 

LOL! funny movie isn't it!! :)

 

did you read all that great info ;)

 

Yeah i did, twice... but i'm still confused... that is just the normal converter.. how do you make the stall "higher" and how does that impact idle? I'm a little confused on that part. It doesn't work technically that you idle normally but when you press the pedal to the metal, the rpm's rise to say 3000 rpm before the 'clutch' per se is released? :confused:

And as far as the great white hype... i've probably seen that movie 15 times... i can't get enough of it. I mean Jeff Goldblum, Sammy Jackson, Jamie Foxx :jester can't be beat.

 

a stall converter will help the car idle better when you have larger cam installed..a bigger duration cam..say you have 3000 stall its not gone to sit there till 3000 then take off ..when you slamm gas down it will get to your power range faster then having a stock converter if you drove it normal around town it would act normal albeit a little slippage..youll need to runa tranny cooler with it also because of the slippage it generates more heat hope that helps.

 

oh ok makes much more sense now. So effectively there is very little resistance until whatever "X" stall is... ?

 

:yesnod:

 

Does this mean that if your stall is 2500rpms you will get slippage until you get to 2500rpm at which time the trans locks up?And if your cam does not start working well until 2500rpms that this slippage will keep the car/cam from bogging down until you get into the cams operating range????Do I have this right??????

 

Hey Jenny nice car I like the color. :D

You have touched on a subject on the face seems like you should get a simple answer but it is quite a complex topic.

Stall convetters are actually torque converters. Some people expect that when they put a high stall converter in their car they will be able to put the car in low gear, apply their foot on the brake and bring the engine up to 5000 rpm, and then let it go as the light turns green. This is not how a high stall conventional torque converter works. They actually work on a torque applied basis.

For example if you put a random converter in a small block 350 it would produce a stall speed in low gear, with a good set of brakes and adequate
weight on the rear wheels of approximately 2500 rpm. If you were to nail the throttle to the floor when the light turns green on the Christmas tree, you would get approximately 3700-4500 rpm flash stall speed.

Now if you put a 427 big block engine in front of this same converter and with the car in low gear, a good set of brakes and adequate weight on the rear wheels the stall speed would be approximately 3000-3800 rpm.
Nailing it from the Christmas tree, approximately 4800-5200 rpm flash stall. The difference here is because of the Torque!

So you really can't say I'm going to put a 3000 stall converter in unless you know what your torque is, also a the higher stall the greater the slippage in high gear which could mean lower ET.

Like I said it is very complex subjectand there's more but I don't want to put you to sleep.

Anyway don't you have a 4 speed in your '80



[Modified by MotorHead, 11:17 PM 11/3/2001]

 

what does Flash Stall mean??? :confused:

 

Thanks for asking this Jenny.
I was going to ask almost the same question, but you beat me to it.

:cheers:

 

WIth you car at idle hammer the gas and as soon as it starts to move look at the tach, that's the flash stall.

 

No, actually it is automatic.. My first. all prior cars were 5 spd. But i'm getting used to it.

 

Ok here it is nice and simple for ya. I have just upgraded my standard converter to a 2000 rpm stall speed.
Ok..if u put your foot on the gas and hold the brake then engine will only rev to a set rpm then stop. This is your converters 'stall' speed. If you try it in your stock vet u should get around 1200-1400 rpm. Dont let the wheels spin.
Now if u put a 3000 rpm hi stall torque converter in you will be able to rev the engine to around 3000 before the engine will hit its 'stall' speed.
Slippage--> Our th350 and 400 converters have an amount of 'slip'. The higher the rpm stall the higher the slip. So even when cruisin at 80mph in top the hi stall will still be 'slipping' more than a conventional converter. I am talking about hundreds of revs here, nothing major.

Uses of High Stall and Slippage--> If the cam is extremely large (5000 to 8500rpm solid cam) it will be very hard to idle at sub 1000 rpm with any load on it at all. So now the converter serves 2 purposes...it shows very minimal load on the engine while it is at low revs. This load increases as the revs increase..allowing a smooth increase during partial throttle opening. So hit the gas slowly and it will rev up to the 5000rpm stall point while smoothly transfering the power from the engine to the trans. By the time the converter is fully 'spooled up' the engine has enough power to keep from stalling. Imaging it like letting out a clutch pedal extremely slowly. Now if u floor the gas in a quick jab causing the engine to accelerate in revs very quickly the tourque converter will 'spool up' very quickly, lauching the car. This is like stepping off the clutch pedal at 5000 rpm. This is where 'flash' comes in. If the converters stall is 5000 it may flash to 5500 when u accelerate at full throttle. U spin the converter faster than it can keep up. This flash is only on initial launch, its stops very quickly. hence 'flash' term. Think of this as clutch slip after stepping off the clutch pedal.
Drag racers use hi stalls for the reasons outlined above and the all important lauch. They sit at the lights with the brakes on hard and the throttle down as far as to pull the engine to its stall speed. Any more throttle and the wheels may spin. (this is where a trans brake is used instead). Light goes green. U step off the brake and go WOT on the gas. The engine is already sitting at its peak tourque revs and will launch like a rocket--if u have the traction!
My vette has 275/60 on the rear so i couldnt do burn outs. I put in a 2000rpm hi stall and now if i step off the brake at 2000 i lay 2 fat tracks of rubber. :) :) :)
Choosing a stall converter depends on many things..engoine power band, gearing, weight, etc..But lets look at basic ones. 2500 rpm is a good starter for a stock to mild 350. This will also allow u to run a lovely hot cam, and be great for burnouts.


[Modified by xrated, 6:04 AM 11/4/2001]

 

thanks x, that helps a LOT! :cool:

 

I have a little piece of info. to add here. My friend has an 85 Corvette, 700-R4 automatic. Engine is a SuperRamed 350 with custom ground cam. While we were out one day with the DiaCom hooked up trying to get some baselines to work with we decided to see if his Hughes 2500 stall lived up to it's name. So we setup up graphs for speed and rpm and went for a few runs. What the graph showed was the maximum rpm the engine saw before the speed sensor saw any mph. I can't remember exactly but I think it was 2650 or something. I guess the converter works!!

 

A very timely topic for me :)
I just had my TH400 rebuilt last week and now I will be shopping for a new torque converter. (My mechanic does not recommend using my 27 year old original equipment converter)
I've done some mods to my 350 so what converter am I going to need.
Here's what I did to the engine.
Bored .30 over
Hyperteutectic (sp?) pistons
9.5:1 compression ratio
Performer intake
Ported and polished heads
Comp Cams 268H cam..218 duration@.050" 454" lift

I am so freekin confused I dont know what to do :confused: :confused:

HELP

Stew

 

If I were u I'd get around a 2200-2500rpm stall. No bigger than a 3000 unless you plan to drag race that thing often.