hheynow
Señor Aceite de Soja
Please explain "stall speed" in layman's terms. 
Please explain "stall speed"
- Thread starter hheynow
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W4RLR
High Tech Hillbilly
In what sense?
In the aeronautical sense, it would be the airspeed where the wings of the aircraft fail to produce sufficient lift to keep the aircraft in flight.
In the automotive sense, I believe it is the function of an automatic transmission's torque converter and engine RPM. Together, engine speed below a certain RPM will fail to transmit sufficent torque from the engine to the transmission. However, I will let sharper mechanical minds answer the finer details of that point.
In the aeronautical sense, it would be the airspeed where the wings of the aircraft fail to produce sufficient lift to keep the aircraft in flight.
In the automotive sense, I believe it is the function of an automatic transmission's torque converter and engine RPM. Together, engine speed below a certain RPM will fail to transmit sufficent torque from the engine to the transmission. However, I will let sharper mechanical minds answer the finer details of that point.
hheynow
Señor Aceite de Soja
In automotive terms as it relates to a torque converter.
jvencius
Full Access Member
rray32539 said:
As a corrolary to that, when you hit the stall speed of a Cessna 172 whilst still ~6-8 feet off of the runway, plan for a change of underwear in your VERY near future (personal experience speaking here...).
Ford_Forgotton
Full Access Member
The more torque your engine makes, the lower your stall speed can be.
Stall speed is the RPM the ENGINE side of the TC much reach in order for the tranny side to begin turning. But thats the OH SO SIMPLE version.
Truth of the matter is, its a combination of engine power, torque curve of the engine, weight of the vehicle being moved, gear ratio of the rear end, and tire height.
Say I get a 1200 stall convertor for my superduty. The THEORY is, that my engine should have to reach 1200 rpm before the TC can begin moving my truck. If I add more weight to the truck, it will actually be even higher RPM, and if I lower my weight, it may take less than 1200 RPM.
Say your car makes absolutely NO low end power. Your going to want a higher stall speed so that the engine RPM is higher in its powerband before the TC begins to transfer that power to the tranny.
Stall really only matters at low RPM anymore because of the LOCKUP TC's. Once a TC locks up, stall means NOTHING! Its direct transfer instead of fluid transfer.
Stall speed is the RPM the ENGINE side of the TC much reach in order for the tranny side to begin turning. But thats the OH SO SIMPLE version.
Truth of the matter is, its a combination of engine power, torque curve of the engine, weight of the vehicle being moved, gear ratio of the rear end, and tire height.
Say I get a 1200 stall convertor for my superduty. The THEORY is, that my engine should have to reach 1200 rpm before the TC can begin moving my truck. If I add more weight to the truck, it will actually be even higher RPM, and if I lower my weight, it may take less than 1200 RPM.
Say your car makes absolutely NO low end power. Your going to want a higher stall speed so that the engine RPM is higher in its powerband before the TC begins to transfer that power to the tranny.
Stall really only matters at low RPM anymore because of the LOCKUP TC's. Once a TC locks up, stall means NOTHING! Its direct transfer instead of fluid transfer.
RickGmi
Full Access Member
I maybe wrong, but as in aircraft and as in automotive, I was under the impression that stall on a vehicle is when the engine can not keep up with the demand and stalls out, like if you could take a car and imobilize it then put it in gear it would increase till the engine could not produce anymore and would just die. like say at 3500 rpm's it just dies, (while not being able to give anywhere,though being imobilized)which i believe is the same as aircraft, the engines can not meet demand and the engines cut off,
Rick your talking specifically about the stall of an engine, hheynow is speaking specifically about the stall speed of a torque converter, the explaination Ford-Forgotton gave is right on.RickGmi said:
whatabudro
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As Daryl stated above
I have a 3500 stall convertor in my Chevy II. The main reason for this is a quicker launch. My car makes plenty of power below 2000 rpm for the average joe, but it real power does not show up until 2500+ rpm. On gassers another important variable is thrown into the equasion, then cam shaft. The cam and the torque convertor must be matched for optimum low end power. I had a 2500-2800 convertor in the car at first but it was not large enough for the cam and tried to engage will sitting still in gear. This resulted in the car lurching at stop lights. I then moved to a 2800-3100 convertor which stopped the lurching but was still unsatisfied with the lowend launches. Finally I hit my mark with a 3300-3500 convertor. Now when I am locked in first gear and flash the go pedal, without hesitation the car hits 3300 rpm loads the rear suspension, raises the front suspension to its full limit and I'm GONE. With my tire/suspension setup this works equally as well on the street as it does at the track.
Bryan
I have a 3500 stall convertor in my Chevy II. The main reason for this is a quicker launch. My car makes plenty of power below 2000 rpm for the average joe, but it real power does not show up until 2500+ rpm. On gassers another important variable is thrown into the equasion, then cam shaft. The cam and the torque convertor must be matched for optimum low end power. I had a 2500-2800 convertor in the car at first but it was not large enough for the cam and tried to engage will sitting still in gear. This resulted in the car lurching at stop lights. I then moved to a 2800-3100 convertor which stopped the lurching but was still unsatisfied with the lowend launches. Finally I hit my mark with a 3300-3500 convertor. Now when I am locked in first gear and flash the go pedal, without hesitation the car hits 3300 rpm loads the rear suspension, raises the front suspension to its full limit and I'm GONE. With my tire/suspension setup this works equally as well on the street as it does at the track.
Bryan
hheynow
Señor Aceite de Soja
Ford_Forgotton said:
Daryl, You're da man!
The reason I asked this question is my tranny is being rebuilt and my upgraded TQ has a stall speed of 2200-2500 rpm. I wasn't given an option as to what stall speed I wanted. IYO, is that the optimal range for my truck?
Ford_Forgotton
Full Access Member
hheynow said:Daryl, You're da man!
The reason I asked this question is my tranny is being rebuilt and my upgraded TQ has a stall speed of 2200-2500 rpm. I wasn't given an option as to what stall speed I wanted. IYO, is that the optimal range for my truck?
2200-2500 seams way to high to me for a diesel engine that redlines at 3250.
I dont know what is considered optimum RPM for our trucks, but I think its alot lower than that.
