what stall converter

[s19243h]

i get different answers from different sorces. some say because the car being 1600 lbs i need a loose converter to from putting the car in nuetral at red lights others say use a stock converter i dont need a stall in a bucket . im getting ready to mount the trans to the motor and wanted to get some opinions before i buy a converter. i have a stock rebuilt chevy 305 268 comp cam 1600-6500 rpm {i was also told to pick a converter 500 rpm over wich would be 2200 stall} 350 tubo trans stock 287 gears and 28" tall rear tires

 

[Lee_in_KC]

Here is a good explanation of converters and stall...

Stall according to TCI

 

[GT63]

i get different answers from different sorces. some say because the car being 1600 lbs i need a loose converter to from putting the car in nuetral at red lights others say use a stock converter i dont need a stall in a bucket . im getting ready to mount the trans to the motor and wanted to get some opinions before i buy a converter. i have a stock rebuilt chevy 305 268 comp cam 1600-6500 rpm {i was also told to pick a converter 500 rpm over wich would be 2200 stall} 350 tubo trans stock 287 gears and 28" tall rear tires

I have a 3200-3500 stall converter in mine (blown SBc and TH350) and it's a blast, but for most I think a 2200-2400 works well. My dad has a B&M 2200-2400 street fighter stall converter in his (327 SBC and TH350) and it drives great.

 

[Mike]

If you really feel you need a looser torque converter, I definitely wouldn't want anything over 500 RPM loose. Even in a 305, that's still a pretty tame camshaft.

 

[s19243h]

If you really feel you need a looser torque converter, I definitely wouldn't want anything over 500 RPM loose. Even in a 305, that's still a pretty tame camshaft.

im thinking 22-2400 would be ideal also , thanks guys

 

[Gerry]

i get different answers from different sorces. some say because the car being 1600 lbs i need a loose converter to from putting the car in nuetral at red lights others say use a stock converter i dont need a stall in a bucket . im getting ready to mount the trans to the motor and wanted to get some opinions before i buy a converter. i have a stock rebuilt chevy 305 268 comp cam 1600-6500 rpm {i was also told to pick a converter 500 rpm over wich would be 2200 stall} 350 tubo trans stock 287 gears and 28" tall rear tires

Stall speed is stall speed whatever the weight of the car. Remember when you are at the llights you are at a stop so the converter should NOT be on stall. To get a converter on stall you normally put your foot on the brake and hit the throttle. The revs you get while holding the car is the stall speed.
There is also a flash stall but let not get in to that now. I use a standard stall converter because I like a soft acting car.

 

[Mike]

Close, but not exactly 100% correct.

Sitting at idle and in gear, the converter is not coupled. It's a terrible over-simplification, but if you set two electric fans face to face and turn one fan on, you will be able to spin the other fan blade with the air coming off the first fan's blades. As you crank up the speed on fan 1, it moves more air and will turn fan 2 a bit faster. Obviously, the magic in a converter is the design of the stator and the strength of the sprag. Window size and angle of the stator can make all the difference in the world in how the car runs.

In the same manner, at low engine RPM levels, the pump is not redirecting fluid efficiently enough for the turbine to overcome the weight of the car with its brakes set. As RPM comes up, the converter starts to fluid couple the pump and the turbine. As the turbine starts moving, then the car starts moving.

A converter's stall speed is the RPM the pump must be turning to create enough fluid flow to spin the turbine.

So an automatic trans car sitting stopped at a light has enough weight (motion resistance or resting inertia) to overcome the converter's fluid coupling ability. The converter is below its stall speed. As RPM increases, the pump begins moving more fluid through the stator onto the turbine, and when the turbine starts moving, the converter is no longer uncoupled.

The trick is sorting where the given engine's torque curve is, gear ratios and weight of the vehicle. You can end up with a really rotten combination where a converter will try coupling at a lower RPM than expected, if the motor doesn't make enough steam. All manner of evil can be covered up in a clutch car, but in an automatic car? The intake, heads, camshaft and converter are all joined at the hip. Roll the cam a couple degrees and suddenly the torque converter doesn't want to play well with others.

Anyone old enough to remember this car -

I bet most of you don't remember who drove the car. :hooray: For those who can, what was it about the torque converter in this car that made it such a giant killer? Bonus points if you can identify the individual that did the converter. Ohhh, the stories I could tell...

EDIT - Don't embarrass yourself by looking at the contingency decals on the car. There's a completely different story behind that.

 

[deckofficer]

Mike,

Anything to do with "Hole Shot" torque converters? That is one of the few high stall speed torque converters I can still remember from the 60's.

Bob

 

[deckofficer]

I think I got it, John Lingenfelter and he campaigned with a Rocky Q-Jet. A carb I have always liked and have used.

 

[Gerry]

Close, but not exactly 100% correct.

Sitting at idle and in gear, the converter is not coupled. It's a terrible over-simplification, but if you set two electric fans face to face and turn one fan on, you will be able to spin the other fan blade with the air coming off the first fan's blades. As you crank up the speed on fan 1, it moves more air and will turn fan 2 a bit faster. Obviously, the magic in a converter is the design of the stator and the strength of the sprag. Window size and angle of the stator can make all the difference in the world in how the car runs.

In the same manner, at low engine RPM levels, the pump is not redirecting fluid efficiently enough for the turbine to overcome the weight of the car with its brakes set. As RPM comes up, the converter starts to fluid couple the pump and the turbine. As the turbine starts moving, then the car starts moving.

A converter's stall speed is the RPM the pump must be turning to create enough fluid flow to spin the turbine.

So an automatic trans car sitting stopped at a light has enough weight (motion resistance or resting inertia) to overcome the converter's fluid coupling ability. The converter is below its stall speed. As RPM increases, the pump begins moving more fluid through the stator onto the turbine, and when the turbine starts moving, the converter is no longer uncoupled.

The trick is sorting where the given engine's torque curve is, gear ratios and weight of the vehicle. You can end up with a really rotten combination where a converter will try coupling at a lower RPM than expected, if the motor doesn't make enough steam. All manner of evil can be covered up in a clutch car, but in an automatic car? The intake, heads, camshaft and converter are all joined at the hip. Roll the cam a couple degrees and suddenly the torque converter doesn't want to play well with others.

Anyone old enough to remember this car -

I bet most of you don't remember who drove the car. :down: For those who can, what was it about the torque converter in this car that made it such a giant killer? Bonus points if you can identify the individual that did the converter. Ohhh, the stories I could tell...

EDIT - Don't embarrass yourself by looking at the contingency decals on the car. There's a completely different story behind that.

Mike
Never going to disagree with you as your expertize and experience far outweighs mine.
Can you clarify something for me.
When a converter is at stall it means that the fluid can not be moved anymore and becomes so to speak 'solid' therefore no slip. It is fully coupled. This happens if the vehicle is not moving and the engine can not overcome the resistance as it has run out of power (bhp and torque). If you put a less viscous fluid in the converter your stall speed would go up. Right?
Where I am confused is where the weight. cam, induction and loads of other things comes in to the stall speed. I realize that at LAUNCH all these thing have a great effect on the initial movement of the car. So are we talking about a different definition of stall or have I got it wrong, because i defiantly don not want to give a fellow Bucketeer the wrong info. To me when we do a stall test its always the max rpm we can get with the car NOT moving.
Your reply would be appreciated.

 

[Gerry]

Mike
Ignore the above post as I did nt get my thoughts right. Please look at this one. Sorry its early and had a bad week with some fighters (cars that is not people)
Never going to disagree with you as your expertize and experience far outweighs mine.
Can you clarify something for me.
When a converter is at stall it means that the fluid can not be moved any faster and becomes so to speak 'solid' (I dont mean solid as in a block of metal as this would be like having the lock up stuck on... engine would stall out) therefore no extra slip. It is fully coupled. This happens if the vehicle is not moving and the engine can not overcome the resistance as it has run out of power (bhp and torque). If you put a less viscous fluid in the converter your stall speed would go up. Right?
Where I am confused is where the weight. cam, induction and loads of other things comes in to the stall speed. I realize that at LAUNCH all these thing have a great effect on the initial movement of the car. So are we talking about a different definition of stall or have I got it wrong, because i defiantly don not want to give a fellow Bucketeer the wrong info. To me when we do a stall test its always the max rpm we can get with the car NOT moving.
Your reply would be appreciated.

 

[ellis8500]

First, some terminology...it's a TORQUE convertor [TC], not a stall convertor. All torque convertors have a stall speed and it does depend on engine torque and vehicle weight. When you read the tech articles they tell you that. What matters is how hard you want to hold the brakes at a stop and how fast the car starts to move, at idle, when you release the brakes. A torque convertor is also a torque multiplier. When the engine side is turning and the trans side isn't, the torque multiplier effect can be two [2] or higher depending on the convertor design. A higher stall speed TC lessens the amount of torque transferred at engine idle meaning less brake pedal pressure at a stop. The TC designed for a 4,000 lb vehicle transferrs enough torque at idle for a smooth take-off from a stop with an engine setup for a low rpm-torque curve. Put that into a 2,000 vehicle and the brake pedal pressure will be higher and the take-off more abrupt. If you want to have a smooth take-off in a light weight car that has a high torque engine then you would want to raise the TC stall speed to a point where the torque transfer at engine idle is lower than stock. The numbers shown above, 2,000 to 2,400 rpm are probably OK since a stock TC is usually in the range of 1,500 to 1,800 rpm. Another way to go, is not worry about the actual number since it really depends on the engine and car it is in. I'm using a Ford engine and tranny so I went to the store and got one that is simply listed as higher RPM than stock which would put it in the 2,000+ range. Call the tech people at the TC company and give them the details regarding engine, car weight and how you plan to drive the car and they will give you a recommendation.

 

[Mike]

Gerry, it looks as if Bill has given you a good explanation.

Trans fluid does change viscosity with heat and that can slightly change the stall speed of a converter. That's on of the reasons you'll notice drivers warming up cars at the race track. Putting heat in the cylinder heads, yes, but also in the trans and the rear end, to thin those fluids down. It's not uncommon to see cars with adhesive-backed heating pads on the trans pans, to help warm the fluid. The warmer fluids move a lot easier, but if you can make engine oil, trans fluid, rear end fluid and water temperatures as close to the same, pass after pass, you are eliminating variables that may screw up something else you are testing.

Another thing to keep in mind is that a standard torque converter will never be 100% efficient. If you go back to my example with two fans, there is no way we can direct 100% of the fluid being moved by the pump side of the converter to the turbine. There will always be losses. And that is where the heat comes in, from those losses. We had magnets in the input shaft of the race car, with a pickup in the front bearing retainer (candlestick). That way I could record engine RPM and input shaft RPM, to see how and where the clutch was slipping. If the clutch didn't have enough counterweight, it might slip in a gear change. If it had too much, it might spin the tires. I'm sure the automatic guys are doing the same thing, so they can watch converter efficiency. It would also let them see how small changes in the stator windows were affecting the car.

 

[40ford]

OK. Inquiring minds want to know.:down: Give us the story on the Vette.

 

[der Spieler]

i get different answers from different sorces. some say because the car being 1600 lbs i need a loose converter to from putting the car in nuetral at red lights others say use a stock converter i dont need a stall in a bucket . im getting ready to mount the trans to the motor and wanted to get some opinions before i buy a converter. i have a stock rebuilt chevy 305 268 comp cam 1600-6500 rpm {i was also told to pick a converter 500 rpm over wich would be 2200 stall} 350 tubo trans stock 287 gears and 28" tall rear tires

I had a 350 with a 272 Comp Cam and a stock converter. Worked fine.

 

[LumenAl]

I had a stock converter on my before I rebuilt the car and I had to stand on the brakes at a light to keep it from creeping forward... it got real old... I went with a 2000 stall... much better... just my experience...

 

[Ted Brown]

I had a stock converter on my before I rebuilt the car and I had to stand on the brakes at a light to keep it from creeping forward... it got real old... I went with a 2000 stall... much better... just my experience...

Al, great to hear from you again you old goat... Mine was chomping at the bit at stop lights, so, out of gear it came, and it also ran a lot cooler out of gear, plus when I clicked it back into gear, we were off and running, real quick like as a matter of fact... Ask all the fellows that tested Her out... and never a tire spin... only at about 75 when she shifted, just a tad ... hehe