Stall converters

[Drache]

Ok this may be a VERY stupid question but since I have never used once and don't know anyone personally that has I need to ask these stupid questions about them.

I know that they are mad to bring your RPMs up to a certain amount and then kick your automatic tranny into first gear... used for racing.

I've heard that people driving Roadrunners around and they told me they had a stall converter.

Are these things legal on roads? I mean do you just sit at a stop light and your engine reves to lets say 3500 RPM before letting you go at that green light or can you ease off without it kicking in?

[RD]

firefighter (ron) and chryco (neil) will give you a great scientific definition of what a stall converter is.  There are two types too, to make it more difficult, loose and tight converters.  They are used to allow the engine to be brought up to its powerband without actually putting too much load on the drivetrain (i.e. lurching you forward). This, in turn, allows the driver to achieve the lower part of the power range of their setup in order to go quicker.  ex.  say your car starts making good torque at 2800 rpm thru 6000 rpms, you will want a torque converter with a stall at 2800-3000 to maximize your launch potential in order to get a quicker time.

Stall converters are necessary on street cars when the camshafts that are being used have such a "lope" to them that without a stall converter the vehicle is an annoyance to operate.  Bad idle situations cause for a annoyed driver (that is if you do not like that stuff).  Some people fix that by increasing their idle speed but that is a temporary fix to a long term problem.

The rpm range of the stall converter needs to be based upon the desired launch rpm of the vehicle, the vehicle's capabilities, and the power range of the motor (based on cam, heads, c/r, rearend gears, etc.).  A high stall converter in a street car (daily driven is not good due to the extreme slipping of the converter during driving causing a higher temperature within the transmission itself.  Usually, street cars go for stall converters in between 2200-2800.  This is mainly due to the duration of many street cars camshafts being in between 270 and 310.

hope this helps, and if anyone else wants to chime in on something i may have missed, please go ahead.

[MYTMOPR]

Well said RD.

One common misconception is the stall will not move the car until its set rpm. This is false. Depending on the size of the stall, the car will take off in the lower 1500 rpm range(and I don't mean at wide open throttle, just a general take off from a stop.)

[MoparYoungGun]

Ok, quick question. Lets say I have a 493 stroker in a Charger. Peak hp at about 5600-5800, peak tq at about 4200-4400. I would need around a 4000 stall give or take but would this hurt drivability on a street driven/highway driven car? Thanks guys!

[RD]

Ok, quick question. Lets say I have a 493 stroker in a Charger. Peak hp at about 5600-5800, peak tq at about 4200-4400. I would need around a 4000 stall give or take but would this hurt drivability on a street driven/highway driven car? Thanks guys!

its not necessarily about the peak hp/tq rating, it is based on the weight of the vehicle, the range of the cam in relation to ancillary components and chassis setup of the car.

[John_Kunkel]

In no way an endorsement of the brand but this page has some good converter info:

http://www.tciauto.com/tech_info/torque_converters_explained.htm

[firefighter3931]

Jamey pretty well covered it and John's TCI   link provides a good technical explanation on the specific compenents within the converter...and their function. The only thing i would add is when sizing the converter, the best performance will be achieved when the converter's stall speed matches the engines torque peak. This helps with the launch and on the 1-2 and 2-3 upshifts by keeping the engine in the meat of it's powerband during the shift recovery process. A high quality converter with looser stall speeds is completely streetable with additional fluid capacity and cooling. I'll be running a 4500 stall (Dynamic 9.5) in my street car with a deep pan and stacked plate tranny cooler. It pays to buy quality when purchasing a converter.  

Ron

[Ghoste]

And call one of the converter makers with a good rep like Dynamic and they can provide you with exactly what you need.  It's definitely an area where you get what you pay for.

[Duey]

Phone Paul at TurboAction...904-741-4850.  Had a good chat with him, also recommended by Ron (FF3931).

I got the 10" tight...17805ST...can't wait to put it in and try it with 4.10's...   

Cheers
Duey

[Chryco Psycho]

using a 4000 stall on the street will be a problem , it will slip most of the time & cause a lot of excessive heat , basically you want enough stall to get into the cam powerband but as low as possible to keep the stall locked most of the time when you are driving it so gear ratio & normal use of the engine become a consideration , for example if you are running 3500 at 70 mph on the highway you really want 3200 max stall   

[firefighter3931]

using a 4000 stall on the street will be a problem , it will slip most of the time & cause a lot of excessive heat , basically you want enough stall to get into the cam powerband but as low as possible to keep the stall locked most of the time when you are driving it so gear ratio & normal use of the engine become a consideration , for example if you are running 3500 at 70 mph on the highway you really want 3200 max stall     

I have to respectfully disagree with Chryco on this one....sorry bud.   I know lots of people who run big stall converters on the street w/o incident. They key is to purchase a converter that has minimal slippage....commonly referred to as "tight" converter. Those units cost more money than your typical "off the shelf unit". ATI, Coan, Turbo Action, Dynamic, PTC all make very streetable high stall converters. A high quality tight converter will have approx 200rpm slippage below the rated stall speed. The reality is that all converters (oem included) have some slippage and will generate heat. How you manage that heat will determine how well the transmission performs and lives under normal driving conditions. A deep pan and big aux cooler are "essentials" for this type of application. The right converter makes all the difference in the world too. I've been in cars with 4500+ converters that behaved just like a stocker for all intents and purposes....until you dropped the hammer !

Everyone has their own "comfort zone" when it comes to these types of setups, so the correct answer is do what's best for you. I have no qualms about running a high stall speed on the street.   It's way too much fun to pass up  

Ron

[Chryco Psycho]

NO problem , it really depends on the person , some like th efeel of loose & high stall converters , some don`t , it definatly has an affct on milage though
Personally I`m not a fan of any converter the clutch gives a way more positive feel + allows the stall speed to vary everytime