Hey guys need your help!!!!!
Thread Starter
1st Gear
Joined: Oct 2010
Posts: 1
Likes: 0
Hey guys need your help!!!!!
Hey guys new-b here. I have a problem with my 01 Vette with the A4 trans. I recently had the transmission rebuilt and went with a 3500 stall torque converter from PDQ. I also removed the 273's and went with 342's. My problem is that I cannot stall my car more than 2500 RPM. I switched my car to competitive driving and I get the same results. What's going on? Is there some sort of programming I need to do or did they just send me the wrong torque converter? The car has been programmed to run with the 342's. Any help would be greatly appreciated. Thanks.
Race Director
Joined: May 2005
Posts: 15,960
Likes: 21
From: West Norriton PA
St. Jude Donor '08
That's a pretty large stall for a street car.
My bet is that you spec'd the wrong converter for your car. There is a lot of factors that effect the stall speed of the converter.
Article on Car Craft
The Hows And Whys of Stall
Converters are rated to stall within a certain rpm range. That’s not because the converter companies don’t know their product; it’s just that your individual engine characteristics and vehicle specs influence stall speed and make a precise number nearly impossible to predict. Even the term “stall speed” itself isn’t perfectly defined. Here are the three distinctions you’re likely to encounter.
True Stall: The rpm the engine cannot exceed when the driveline is locked. The most accurate way to determine true stall is by locking First gear and Reverse with a transbrake and observing engine rpm at wide open throttle (WOT).
Flash Stall: The rpm the engine “flashes” to when launched from rest at WOT. A converter will often briefly flash to a higher rpm than its true stall speed.
Brake Stall: The rpm the engine cannot exceed with the brakes locked and the driveshaft not spinning. Brake stall isn’t usually an accurate measuring tool since the engine often overpowers the wheels before the true stall speed is reached.
When a converter company quotes you a stall speed, verify whether it’s flash stall or true stall. Most converter companies quoted us flash stall figures. Many factors determine where the converter will flash stall once it’s installed in your car. Heavy cars with tall (numerically low) gears and large-diameter tires offer more resistance to forward motion, so the converter will stall at a higher rpm than it would in a light car with steep gears and short tires. The easier the motor can accelerate the vehicle, the lower the converter will need to stall to get the car moving.
Of course, the power and torque curves of your motor will have a huge effect on stall speed. Generally speaking, engines that produce more low-end torque will bump the stall speed to a higher rpm. Conversely, the same converter will stall to a lower rpm behind a less torquey, higher-winding engine. Converter companies often designate the former as “big-block” and the latter “small-block.” When you buy a typical converter that’s rated at 2,000-2,500-rpm stall, that rating is meant to span a variety of motors with different power curves. Scott Miller of TCI points out his company’s 12-inch Saturday Night Special converters typically stall at 1,600-1,800 rpm behind a 325-375 lb-ft “small-block” and up to 2,000 rpm behind a 400-450 lb-ft “big-block.” Sure, they’ll stall even higher behind a torquier motor, but they’re intended for mild, conservatively cammed motors.
Miller explains that any converter’s size limits the amount of torque it can safely handle. Although larger-diameter converters have bigger parts, that’s not always a good thing. Larger fins mean the fluid can exert more bending forces and result in failure. In stock form, bigger converters also allow more torque multiplication and lower potential stall speed, but the internals can handle only so much torque before parts start breaking. Reducing the diameter of the converter reduces its ability to multiply torque, puts less stress on the fins, and raises the stall speed, so small converters are generally better suited to peaky high-performance engines with higher-winding powerbands.
Other internal tweaks, such as fin angle and stator design, can have enormous effects on the converter’s fluid coupling, which changes stall speed and torque multiplication. So it’s possible to build a “tight” 2,600-stall converter or a “loose” 4,000-stall converter in identical 10-inch housings, just by varying the internal design. Most internal mods are proprietary, but building a converter to achieve the right flash stall while maintaining around-town driveability takes a combination of proper stator design and fin angle in the correctly sized case. While it may be possible to build a 7,000-rpm 11-inch converter, it’d be horrendously inefficient—starting with an 8-inch converter housing would be a smarter choice.
My bet is that you spec'd the wrong converter for your car. There is a lot of factors that effect the stall speed of the converter.
Article on Car Craft
The Hows And Whys of Stall
Converters are rated to stall within a certain rpm range. That’s not because the converter companies don’t know their product; it’s just that your individual engine characteristics and vehicle specs influence stall speed and make a precise number nearly impossible to predict. Even the term “stall speed” itself isn’t perfectly defined. Here are the three distinctions you’re likely to encounter.
True Stall: The rpm the engine cannot exceed when the driveline is locked. The most accurate way to determine true stall is by locking First gear and Reverse with a transbrake and observing engine rpm at wide open throttle (WOT).
Flash Stall: The rpm the engine “flashes” to when launched from rest at WOT. A converter will often briefly flash to a higher rpm than its true stall speed.
Brake Stall: The rpm the engine cannot exceed with the brakes locked and the driveshaft not spinning. Brake stall isn’t usually an accurate measuring tool since the engine often overpowers the wheels before the true stall speed is reached.
When a converter company quotes you a stall speed, verify whether it’s flash stall or true stall. Most converter companies quoted us flash stall figures. Many factors determine where the converter will flash stall once it’s installed in your car. Heavy cars with tall (numerically low) gears and large-diameter tires offer more resistance to forward motion, so the converter will stall at a higher rpm than it would in a light car with steep gears and short tires. The easier the motor can accelerate the vehicle, the lower the converter will need to stall to get the car moving.
Of course, the power and torque curves of your motor will have a huge effect on stall speed. Generally speaking, engines that produce more low-end torque will bump the stall speed to a higher rpm. Conversely, the same converter will stall to a lower rpm behind a less torquey, higher-winding engine. Converter companies often designate the former as “big-block” and the latter “small-block.” When you buy a typical converter that’s rated at 2,000-2,500-rpm stall, that rating is meant to span a variety of motors with different power curves. Scott Miller of TCI points out his company’s 12-inch Saturday Night Special converters typically stall at 1,600-1,800 rpm behind a 325-375 lb-ft “small-block” and up to 2,000 rpm behind a 400-450 lb-ft “big-block.” Sure, they’ll stall even higher behind a torquier motor, but they’re intended for mild, conservatively cammed motors.
Miller explains that any converter’s size limits the amount of torque it can safely handle. Although larger-diameter converters have bigger parts, that’s not always a good thing. Larger fins mean the fluid can exert more bending forces and result in failure. In stock form, bigger converters also allow more torque multiplication and lower potential stall speed, but the internals can handle only so much torque before parts start breaking. Reducing the diameter of the converter reduces its ability to multiply torque, puts less stress on the fins, and raises the stall speed, so small converters are generally better suited to peaky high-performance engines with higher-winding powerbands.
Other internal tweaks, such as fin angle and stator design, can have enormous effects on the converter’s fluid coupling, which changes stall speed and torque multiplication. So it’s possible to build a “tight” 2,600-stall converter or a “loose” 4,000-stall converter in identical 10-inch housings, just by varying the internal design. Most internal mods are proprietary, but building a converter to achieve the right flash stall while maintaining around-town driveability takes a combination of proper stator design and fin angle in the correctly sized case. While it may be possible to build a 7,000-rpm 11-inch converter, it’d be horrendously inefficient—starting with an 8-inch converter housing would be a smarter choice.
