OK a torque converter converter converts the flywheel power to my auto trans right? WHAT IS THE DIFFERENCE BETWEEN TORQUE CONVERTERS? What is "Stall speed" and why is it important? How does different stall speeds affect your vehicle and how do you choose?
Knowledgable people need only reply. Thanks in advance.


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a torque converter has two "fans" in asealed container, one "fan" is attached to the trans, the other to the crank of the motor. Inside the converter is liquid, as the crank turns one fan the fan attached to the tranks is forced to move, well not forced but almost. Im not quite sure what the stall number means but i know it has something to do with how much grip it has or something like that

I've been meaning to ask about torque converters also, since I have an auto and have read on different forums that a tall torque converter will help an auto get into the 12s. The part that confused me was that I think I read somewhere that if you get the TCI 3000 it means that you have to rev the car to 3K RPMs for the car to start moving or something to that effect. Doesn't that mean that you're going to have to accelerate the car a whole lot more just to move an inch, like when you're stuck in traffic. I might just be mistaken so I would really appreciate it if someone could clarify that for me.

I don't think that's the case... I think stall means where it firmly starts to engage... under normal conditions I believe it still drives the same. When you bury the pedal, and hold the brake, a 3000 stall would mean it revs to 3000 rpm...


I'm not sure, I have a manual... I know a few guys with older muscle cars that are autos


George

two second search reveals:

http://auto.howstuffworks.com/torque-converter.htm

great link, but it didnt explain stall speed, and the question about it above. anyone else know?

Lets see if the Professor can help.... Stall Speed is simple, yet confusing...


Stall is the speed at which the converter will hold the engine speed and not allow any further gain in RPM. (i.e., the engine "stalls"). That is to say, if you go WOT with your wheels locked, the engine would not go any further in RPM then the stall speed at which point it would either stall/die or just lug out at that RPM, unti you release the brakes. The Stall speed rating on your converter is the RPM at which the power transfer is most efficient. Below the Stall Speed - lots of slip - at and above the stall speed - near lock transfer.

The simple answer - you want a converter with a stall speed just below your “Sweet Spot” of Horsepower output RPM for maximum performance, however that wouldn't work very well for everyday driving as your engine would overrev every time you want to take off..

The more complicated answer involves as much the engine then the Torque Converter. The speed at which stall occurs with a given converter is a function of engine peak torque. 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, but it will give you a general idea.

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 speed 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. 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.

Stall speed should be matched to engine performance, the car weight, tire size and gear ratio. Proper selection of stall spec will make for quicker launch, better 60 ft. time and better ET. It is very important that these parameters be specified when ordering a converter to assure satisfaction.

While stall speed is very important it is by no means the only consideration when selecting a converter. Torque multiplication at launch and high-end efficiency are equally important. Stall speed can be attained in many ways that cripple the converter in other ways. Stall speed can be obtained at the expense of looseness at low speeds and loss of performance at higher speeds after launch. You want a converter that produces the right stall without sacrificing performance down the street or down the strip.

Stall speed is also affected by the torque converters efficiency ratios. Some brands are very efficient, and will stall the engine earlier in the RPM curve, while others are not as efficient, so there is always slip requiring a lower stall speed to get the HP to the wheels. Finding the correct stall speed will require a bit of experimenting depending on make/model of converter as well as engine performance statistics.

Stall speed= stock are cars have 2450 stalls. That means that if you hold your foot on the brake and your other foot on the gas it will rev to 2450 without spinning the tires. By coming off the line at a higer rpm supposing you get traction you will cut much better 60 ft times and it will get you a lower e.t. If you just take off normally it will not rev up to the top stall speed before it goes. Usually the number is a little higher than what it will actually do. Like the one in mine is the stock 2450, mine starts to turn the tires over after 2300 rpm. Coming off the line higher in the rpms puts you in the power band even quicker. Usually to get the good times with the stall you need drag radials, you come off the line that high on street tires and usually nothing but spinning will happen. Hope this helps. If not pm me and I will try to explain it better.

EDIT- Professor Wizard, you beat me to the punch:D, you explenation is much better than mine.

More info can be found here (http://www.summitracing.com/landing/mustang/ln_02feature.htm?ID=%7B82417BC5-2BB2-4CBA-88AC-2C8F6A37BBC8%7D&Type=5)

I was going to answer his question but thank goodness I read through the other posts first and saw wizard's response. It is not possible to explain any better than that. Well put, professor!!:)

On a side note, it is a good idea to use 2 tunes with seperate settings on your converter. One for street and one for the track on drags or slicks. Obviously as pointed out by 757GT.

757....

NA... mine wasn't better... just more detailed... you put it well with your description too!

Should we get into the difference between locking converter systems - that is another world in and of itself!

damn!! thanks Professor and 757! I'm all set now, no wonder I visit these forums pretty much everyday!
[sm=thanx.gif]

want to know how much difference there is with the proper converter?
stock converter my 60' all time best 1.994 and e.t. 13.36
TCI custom 3800rpm stall converter first pass without a reflash 60'= 1.842 and e.t. 13.08
that run was made under less than ideal conditions with spare onboard and full tank of fuel. approx. 75 extra lbs. had all things been equal weather and car that pass would have been 1.80 and 12.95
on the dyno(mustang dyno) before being reflashed for the converter my car made about 267hp and 273tq. after some magic tuning by jj@ woodbine performance we laid down 282rwhp and 322tq.
my peak tq is now at 3300rpm vs. 4400rpm previously. this is the torque multiplication effect the prof. reffered to. at 3300 rpm we were able to increase torque by 73ft.lbs.!!!! and my peak was raised by 49ft.lbs due to sctxcal2's ability to adjust converter lock-up %'s. the difference in my car now and from stock is like having a s/c or 100shot of n20. street driving is affected very little due to the l;ockup function. i do have 2 tunes one for race and one thats no so aggressive for street.
anyone with an auto should seriously consider this mod.

I ordered a Kenne Bell SC 8psi a couple of weeks ago (still waiting) and part of the build up is that they build a custom tune based on what you have installed. About the time that I ordered the SC, I also ordered a TCI Street Fighter TC with a 3000 stall. I told them that this will be installed by the time the SC is done. The next day they called and told me that they did not recommend the TC because they felt it would come on too strong. That was the only explanation I could get so for the time being, I held off on the TC (still in the box in my garage). I was thinking that their concern was with the cars drivabilty around town but was wondering if anyone else had any thoughts or suggestions?

the roots style SC makes good low end power consider increasing stall speed. i also want TCI 3000 however no SC is in the near future only N/A mods to this point. CAI/3.73 GEAR/LT HEADERS/X PIPE/STEEDA UD PULLY'S etc.

would a TC do a v6 any good?

simple explanation -

a torque converter is to an automatic what a clutch is to a manual

stall speed is the rpm at which the converter "locks", applying full power to the transmission

a torque converter has two opposing hubs that spin and "lock up" or "stall" at a given rpm

at rpm below "stall speed", the converter is slipping, like a clutch that is not fully disengaged

I like the proffessor's thorough explanation, just thought this might be simpler

I cant find a torque converter for our Stangs anywhere... anyone have a link to some place that sells them?

I don't want to spoil your fun, but the reality is you don't need one. unless your car is a track only car, it's not worth the driveability you will lose. There are plenty of mods with much more bang for the buck. If you want to raise your launch rpm, trade your car in for one like mine - where the torque is applied with your left foot lol. Unless youre planning on goin low 11's or faster it's really not worth it. There are plenty of mustangs out there haulin ass with the stock converters.

summitracing sells some with a 3000 rpm stall speed

ORIGINAL: RodeoFlyer

I don't want to spoil your fun, but the reality is you don't need one. unless your car is a track only car, it's not worth the driveability you will lose. There are plenty of mods with much more bang for the buck. If you want to raise your launch rpm, trade your car in for one like mine - where the torque is applied with your left foot lol. Unless youre planning on goin low 11's or faster it's really not worth it. There are plenty of mustangs out there haulin ass with the stock converters.


Agreed. I have an auto (bought it so my wife can drive the car). should not have done that. Anyhow, better off with a 4.10 rear end and ratchet or dual gate shifter. I found out that B&M is about to release a ratchet style shifter for the 2005+ autos. Gets you quick and you could auto x with the ratchet shifter. Otherwise take the depreciation hit and buy a manual.

Oh by the way, if you are bracket racing an auto is more consistent and as such you should prefer the auto over the manual.

A Torque Converter transefers engine rotation to transmission rotation by spinning the fluid at a high rate of speed. The higher the stall the more RPM needed to get full power to the wheels, for example a 3,000 Stall will not transfer 100% of the power until 3,000RPM until then its almost like slipping the clutch on a manual. Torque converters a crucial to automatic tranny's. My friend put in a performance converter in his Marauder and it made a night and day difference in acceleration.

ORIGINAL: RodeoFlyer

I don't want to spoil your fun, but the reality is you don't need one. unless your car is a track only car, it's not worth the driveability you will lose. There are plenty of mods with much more bang for the buck. If you want to raise your launch rpm, trade your car in for one like mine - where the torque is applied with your left foot lol. Unless youre planning on goin low 11's or faster it's really not worth it. There are plenty of mustangs out there haulin ass with the stock converters.


I don't agree. Like I said My friend put in a converter on his 2003 Mercury Marauder and it was worth every penny. There are converters out there that do NOT affect driveability as far as everyday driving in a negative way.

Excellent information all around....

Something else that I didn't see clearly pointed out is that you should match your torque converter to the type of camshaft you are using. This is where I believe the Professor touched on matching your stall just under the "sweet spot" of where your HP and torque curves cross. Aftermarket parts and camshaft changes will alter where that crossover occurs. And a higher stall will end up costing you more in gas. I run a 3000 stall on a 355 V8 and get 12 MPG on the highway.

Either a V6 or V8 can benefit from a different stall, as long as it's correctly matched up. HP is no good, if you don't have enough torque to jump off the line.

Hoose84

Other than allow you to rev up to certain rmp before launching, what other benefits does a torque coverter provide?

torque converters actually multiply the ammount of torque your engine produces. The presence of a stator allows the fluid in motion to remain in motion, this provides an "assist" in regards to the engine's ability to spin the turbine. Think of this principle as a "redneck pool" affect. You ever run around a small, above ground pool until the water begins to push against your back? Then you can just lift your feet and float in a circle around the pool? Something similar happens in a converter but on a much more complicated scale. Now this will not double or triple the ammount of power your engine makes, but it allows it to produce the same crankshaft speed under load than a converter without a stator (which does not exist). Sometimes when the stator breaks (allowing it to freewheel in either direction) you will notice that your car just revs and barely moves out of it's own way from a stop but will cruise like normal. This is the engine working extra hard to obtain the same amount of driving force than it used to.
The right torque converter is one that allows moderate amounts slippage until the engine produces peak power. A 302 with an f series cam will benefit from a 3000 stall because the engine does not produce a lot of torque below 3000rpm (f cam is made for high-end power). You want to be able to rev the engine to it's power band and, upon release of the brake, have a near direct link between the engine and the tires. This allows for the fastest acceleration (engine at full steam directly linked to wheels = wheels equal engine's speed quicker than allowing slippage of t/c from a normal accel). This and the lack of a third pedal to push is, in my opinion, the only benefit of an automatic. Unless you are a teenage girl or a flat-out drag racer, I believe the manual trans offers more control and reliability. I prefer a stick to an auto ANY day of the week.