Howdy!

I was wondering about the so called "stall speed" of torque converters. Isn't that directly related to how much power is going into the torque converter? In other words, if a 300 HP engine stalls a torque converter at 2000 rpm, wouldn't a 400 HP engine be able to turn the same torque converter at a higher stall rpm? Or is stall speed at a standard HP level?

Thanks,
Tad

 

stall speed is relative to torque NOT HP along with weight, gear ratio and tire size.

bill

 

If a TC is attached to an immovable object, the the stall speed is only going to be related to power, since it's RPM related. Torque * RPM = power. Tire size, gear ratios and the like have nothing to do with the absolute stall speed of a TC, they only affect the amount of resistance against the engine at a given speed and load, which is what I think bill is saying.

I'm talking about a TC attached to a shaft that cannot move. To say that the absolute stall speed is X rpm, I would think that would have to be at a given power level.

Tad

 

I think the stall speed is related to the "efficiency" of the converter. It will also take a certain amount of HP to drive the converter, but the stall point is when does the design efficiency prevent "slip" in the TC.

 

Mostly correct, if the trans is in drive and the brakes are held to prevent the wheels from turning and the engine rpm is increased the resistance load is increased. When the engine gets to the rated stall speed of the converter and the rated power output the converter is said to have "stalled" and regardless of the amount of throttle given the RPM's will not increase. Stall speed is related to both efficiency and stator pitch. But yes if the engine is putting out more power than the rating of the converter then yes you can push the "stalled" RPM's past the rated stall speed.

 

I'm talking about a TC attached to a shaft that cannot move. To say that the absolute stall speed is X rpm, I would think that would have to be at a given power level.

the stall will still change RPM's if you change torque input so if you want to compair coverters that would be one way ie constant torque input and a non movable shaft. being as every truck ( or car ) is diffrent you cant give an absolute stall. the converter builders can only give an approxamation of stall if givin the info for your truck. example, we use to use a vega converter as a cheap high stall for a hot rod. in the stock vega the stall was approx. 1800-2000 rpm but once it was put in a 3500 lbs car with a strong small block the stall went to 3500 + so as from this I hope that you see it cannot be sold as an absolute stall #

bill

 

Right. So, there is no standard power input level for a torque converter stall speed, just numbers that are approximations for a given TC used in a typical environment for that torque converter.

The only way numbers could truly be comparable, then, would be if manufacturers would publish the power level a torque converter was rated at.

Tad

 

the latest way to show approx stall is what is called K factor. do a google on that and have fun doing a lot of reading .

bill

 

with the TC u have two sides...one is driven by the engine and then that one drives the other which drives the transmission. If someone attached a boat in the jersey harbor to ur truck...u would rev up to the "stall speed" aftre which there would be no more revving...either at that rpm u get the load moving or there is no more increase in rpm.....u will rarely see that...but anyway if u hook up something heavy then ur engine will revv up to say 2200rpms after which it will stay there for a bit until it gets the other side of the TC moving and then the truck starts to move and u will rev further. until that 2200 rpm there is torque multiplication going on with the way the stator is shaped and splashes the oil around to create momentum within the TC.....normally in a diesel u would think that a TC that stalls right at the torque peak would be best but then u gonna think about having the rpms high enough to build boost....although boost is controlled by fuel not rpms but thats another story...most guys get something around 1800-1900rpm stall and like 2200-2300 for racing

 

yes a higher hp engine or a greater load will stall the TC at a higher rpm but really shouldn't by very much if the TC is built tight and is efficient