How do they work? What exaclty is stall speed? How does having a higher stall speed for performance engine applications better than a lower stall?

 

A torque converter is basically a fluid coupler between the engine and transmission. At low rpms they do not transfer the torque of the engine to the transmission acting like a clutch in a manual application. At some point with rpm the converter applies enough force to the input of the tranny that it will begin to move. Up to this point it is stalled. Having a higher stall speed acts in the same way as side stepping the clutch in manual car. It allows the engine to get into its power band and accelerating quicker.

 

So that means that it has to rev more befroe moving. So if I go from stock(whatever that is) to a 3000 stall, then I have to get on the gas more to move.

 

It will move probably right off idle or just letting off the brake. It won't have full torque available. Will feel like a slipping clutch kind of when you give it part throttles. To accelerate at the same rate as the stocker at part throttle just driving around will require more throttle.

Have a read here. They do pretty good job explaining things here. Much better than I can.

TC Faqs

 

All torque converters have a "stall rpm". Stock ones are typically low due to driveability issues, heat, and mileage concerns. Just because an aftermarket converter has a higher stall speed than stock does not mean the vehicle will not move until that rpm. All it means is that until the stall speed rpm the wheels will not see 100% (theoretically) engine power. The power input to the wheels is exponential and by using a higher stall conveter you just move that curve to the right (more rpm) The outside of the converter is attached to the flywheel and the inside is attached to the input shaft of the transmission. They are not directly hooked by any means. The only medium between them is the transmission fluid Inside is a series of fins (i.e. mini airplane wings) which are directed in opposite directions. Due to the angle of the fins the stall speed can be changed. Its the same principal of an airfoil (spoiler, airplane wing, etc) At a certain angle (depending on size, area, wind speed, etc) the airfoil will no longer create lift and the technical term for that is "stall", hence the reason for "stall" converter. For example with a 3000 stall torque conveter (unlocked), at 1000 rpm it may be only allowing 10% of engine power to reach the wheels, and 1500 it may only allow 30% and so on and so forth until around 3000 where, in theory, it will allow 100% of the engines power to transmit through the transmission.

 

So you would not want all engine power at a lower RPM. It sort of seems if your engine is weak you would want a high stall speed and a powerful engine would want a low stall speed.
And are all converters lock up at a certain RPM or are there special lock up converters and what are the advantages.

 

not necssary a weak engine.but when you do a cam swap the new cam will probably move your low end tq to a higher rpm so to get all of the advantage you want the verter to flash to get all the tq of the line.If not if you put a bigger cam and stay with stock verter then the best way i know you can tell the verter is to small if you take off from a dead stop r a slow roll and nail it the truck will feel like it is taking off twice the track is really the best place to feel this and some dr tires.
sometimes you can get by with alot of gear instead of stall but alittle of both is better.all depends on the duration and lobe center line on what size stall to get some may agree and some may disagree but imo the best all around stall is around 2800 to 3000.10.r 10in if you don't tow and a 12in if u do tow

 

Most if not all TC's manufactured today are lockup. An actual clutch within the the TC that mechanically locks the engine to to the trans. Done for gas mileage and they usually lockup at cruise conditions. Most are electronically controlled and the speed and conditions at which they lockup are programmable.

 

I put my first stall in a few months ago. At first you wonder if something is wrong because it feels so different. When I put the truck in gear and let off the brake it didn't move, at all. Usually your truck will creep forward. Mine now does creep, the converter has tightened up a bit I guess. Basically, whatever your stall speed is where the rpm will shoot up (flash) to if you stomp it off the line. Mine is 2600. So at a red light, if I stomp it when it goes green, the rpm's flash up to 2600 and then I start moving. (actually the tires start spinning ) Instead of easing into your torque curve you are slammed into it by the rpm's that built up. You will receive a corresponding reduction in MPG, but its not really that bad. Also, a bigger stall allows less rpm drop between gear shifts which keeps you in your power band. Rumor is a good stall is good for a .5 second drop in your 1/4 mile et.

 

ANy one in here have any Suggesttions for brands of TQ-converters? And what prices they are for a 3000 stall.