Torque converter stall speed question...

[shone190]

Hi guys,

   I read so many articles regarding torque converter stall speed but I still have some concerns.

My main question is, what is the difference between, for the example, 1200rmp and 2800rpm stall speed converters?

As I understood, first converter will be fully engaged after 1200rpm, and the other after 2800rpm. So, if I never have a need to race with the car with left foot on brake pedal and right on the gas pedal, I will only see difference in fuel consumption between two of them?

Also, if I started from stop light "normally" with using only right foot (depress brake pedal and press gas pedal), the car will be quicker with 1200rpm stall converter because it will be sooner fully engaged?

Am I right or I missed something?

Thanks to all in advance.

[Brass]

Hopefully someone who can explain it better than I can will jump in, but I'll take a shot at a response.  The stall speed of a converter does not mean the engine has to reach that rpm for the converter to engage.  A stall converter will let an engine's revs enter its power band sooner, which is typically at higher RPM in performance engines with long HP/TQ curves.  

The two converters you mention, with stalls of 1200 and 2800, will both behave normally under normal driving conditions.  If they are quality converters, most of the time you wouldn't even notice the difference.  But under WOT, the 2800 stall converter will allow the engine to "flash" into peak power before the 1200 one would.  Theoretically, the engine with the 2800 converter behind it would be faster because the other engine would be fighting against a converter that is limiting it to 1200 and delaying the engine from entering its power band.  For comparison, if you think of a converter like a clutch, the 2800 converter is like revving the engine before dumping the clutch.  The 1200 would act as if you dumped the clutch without revving the engine.  It would just lug and take a lot longer to start making power.    

I don't know how gas mileage would compare.  There may be a little loss of efficiency with the higher stall converter but whatever it is, it is probably negligible.  

Cam, gear, and tire diameter all factor into choosing the right converter.  I think there is also a distinction between loose and tight.

Here is a good link for more info:

http://www.badasscars.com/index.cfm/page/ptype=product/product_id=78/prd78.htm

[Nacho-RT74]

I allways describe the stall speed like the speed you make a full release of the clutch pedal  on a manual tranny car. While you are releasing the clutch, the car moves with more or less torque, according the engine revs, car weight, static inertia, etc...

Or kinda of LOL

[shone190]

Thanks for the answers, so if I have 2800 stall converter and driving through the city where rpm will never reach 2500rpm, that will be like I always have pushed clutch pedal a little or more?

[justcruisin]

Not really, under lighter loads you shouldn't tell any difference if the converter is built right.

[shone190]

Anyway, much better option is TKO600, but also much more expensive too

[John_Kunkel]

In reality there is no such thing as a "1200 converter" or a "2800 converter"....the stall speed of any converter depends on the power input and the holding ability of the brakes. IOW, a given converter might stall at 1400 behind a /6 and the exact same converter might stall at 2800 behind a Hemi. The factory stall speed charts are an example of this, the exact same converter stalls at different speeds depending on the motor it's bolted to.

In addition, a converter with an advertised stall speed of, say,  2500 can be built either "loose" or "tight" so that the part-throttle slippage will be less or more....so a definite difference in fuel consumption could be seen depending on the vehicle it's installed in.

Stall speed is a convenient way for manufacturers to advertise their converters but stall speed is deceptive...there's a lot more to it.

[c00nhunterjoe]

In reality there is no such thing as a "1200 converter" or a "2800 converter"....the stall speed of any converter depends on the power input and the holding ability of the brakes. IOW, a given converter might stall at 1400 behind a /6 and the exact same converter might stall at 2800 behind a Hemi. The factory stall speed charts are an example of this, the exact same converter stalls at different speeds depending on the motor it's bolted to.

In addition, a converter with an advertised stall speed of, say,  2500 can be built either "loose" or "tight" so that the part-throttle slippage will be less or more....so a definite difference in fuel consumption could be seen depending on the vehicle it's installed in.

Stall speed is a convenient way for manufacturers to advertise their converters but stall speed is deceptive...there's a lot more to it.

Beautifully put. This is exactly why you will hear alot of us reccomend a 9, 10 or 11" converter instead of saying a 2500, 3000, or 3500.
For example, the converter i had in my 383 car would flash at about 2900, pulled it out and put it behind my 440 car and it flashed at 3500.....

[Nacho-RT74]

magic world inside a TC