I have a Vigilante 10.5" 3 disc lockup converter stalled at 3200Rpm's and am curious what rpm it flashes at? Is there a way to calculate this? I'm assuming 3200 is the brake stall speed. The car isn't running right now so I can't just get in it and find out.
How do I determine my converter flash rpm?
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From TCI website:
Stall speed is a measurement of how high a converter will flash in a specific application due to engine torque and load. The "flash" point, simply put, is the rpm at which a car moves from a dead stop under full load. The torque converter's diameter, fin angles, internal parts clearances, and stator design are some factors that determine stall speed. Matching stall speed to a given application is critical for optimum performance, but the advertised stall speed of a torque converter is just a ballpark figure. "Stall speed varies depending on the load placed upon the converter from the engine and the vehicle weight," explains Stan. "If you have two vehicles with identical motors and rear gear ratios, and the only difference between them is vehicle weight, the same converter will stall more in the heavier car, because it sees more load. Likewise, if you have two identical vehicles with the exception that one produces an extra 100 lb-ft of torque, the vehicle with more torque will flash its converter 200 or 300 rpm higher, so this should all be taken into consideration when choosing a converter.
Stall speed is a measurement of how high a converter will flash in a specific application due to engine torque and load. The "flash" point, simply put, is the rpm at which a car moves from a dead stop under full load. The torque converter's diameter, fin angles, internal parts clearances, and stator design are some factors that determine stall speed. Matching stall speed to a given application is critical for optimum performance, but the advertised stall speed of a torque converter is just a ballpark figure. "Stall speed varies depending on the load placed upon the converter from the engine and the vehicle weight," explains Stan. "If you have two vehicles with identical motors and rear gear ratios, and the only difference between them is vehicle weight, the same converter will stall more in the heavier car, because it sees more load. Likewise, if you have two identical vehicles with the exception that one produces an extra 100 lb-ft of torque, the vehicle with more torque will flash its converter 200 or 300 rpm higher, so this should all be taken into consideration when choosing a converter.
Turbo6Smackdown
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And that's not affected by how well your back brakes work?
Dusty Bradford
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The true flash stall of the converter is the rpm which the engine flashes to when launched. On a data log you will see the rpm climb quickly then roll over. The point where the converter rolls the engine rpm over is the flash stall. This rpm is also the point where the converter tends to drop back to on the gear change.
If your car drops back to 4800 rpm on each gear change you can say your converter flashes to 4800 rpm. If the car is launched at 4000 rpm you should see the rpm on the data log roll over around 4800 rpm as well.
This is because turbo cars build torque as they build boost, which in turn builds more rpm by pushing against the converter........which in turn builds even more boost (torque), which pushes even harder on the converter driving the stall speed even higher......and it just goes on and on.
Some will call the flash stall the rpm at which the engine initially jumps to before it builds any boost. This is easy to notice with a trans brake by engaging the brake at idle and stomping the gas. Most 10" converter will jump to around 3000 rpm.
If your car drops back to 4800 rpm on each gear change you can say your converter flashes to 4800 rpm. If the car is launched at 4000 rpm you should see the rpm on the data log roll over around 4800 rpm as well.
This is because turbo cars build torque as they build boost, which in turn builds more rpm by pushing against the converter........which in turn builds even more boost (torque), which pushes even harder on the converter driving the stall speed even higher......and it just goes on and on.
Some will call the flash stall the rpm at which the engine initially jumps to before it builds any boost. This is easy to notice with a trans brake by engaging the brake at idle and stomping the gas. Most 10" converter will jump to around 3000 rpm.
vacuum 6
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Do I understand this correctly, my guess is no. If an engine drops back to 4800 on shifts then the flash is 4800. Now regarding the 10" at 3000, so the engine will drop back to 3000 between shifts?
How's that going to tell any useable information?? What if he has really good rear brakes? What if he has really crappy rear brakes?
Just a Six??
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This seems the easiest way to get a good aproximate idea of flash point.
Useable?
Well if you need to know down to the singular RPM do as others have recommended.
You want a general idea, the method I have described has been used for years.
There's a point where the engine revs then flattens out - I would assume that is your general stall.
If you are placing bets on it....don't use my method.
Well if you need to know down to the singular RPM do as others have recommended.
You want a general idea, the method I have described has been used for years.
There's a point where the engine revs then flattens out - I would assume that is your general stall.
If you are placing bets on it....don't use my method.
Just a Six??
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If you have good rear brakes Pump them up & see what it takes until boost comes in at when you floor it. Or E-Brake. Easy that way to get an idea.
I just called Precision and the stall you specify is flash stall. I was pretty sure my converter would footbrake at a pretty low RPM and hit 3200 when i launched it. Combine that with a couple pre-turbo exhaust leaks and it made getting initial spool to happen a bit tough. i started reading about what converters flash at vs. foot brake stall and began to wonder if mine was too loose for my TE-44. I'm now starting to wonder if it is too tight. What does a stock converter flash at on average??
Car is in pieces for a couple more months.
Dusty Bradford
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That's what most converter builders will call a flash stall. The rpm which the engine flashes to when launched....which is generally the same rpm the engine drops to on the gear changes.
Turbo stall talk can be very hard to understand. But... no a 3000 stall will not drop back to 3000 rpm on the gear change. 3000 will be the rpm at which you begin seeing boost.
I can make a 2800 stall 10" stall anywhere from 2800 to 4400....it all depends on how good the brakes can hold. At 2800 you have 0-1# of boost. 4400 you may see 12#.
Footbraking the car until the tire spins don't tell me anything from a converter standpoint. It will stall different in a slick garage vs a sticky track. I go by the rpm at which you begin seeing boost and the rpm at 5psi if I need it.
vacuum 6
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Thank you.
TurboTnZ06
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You're saying the same converter would stall higher at 0psi boost with a fully ported and cammed stroker with a 67mm turbo compared to a bone stock engine and turbo at 0psi boost?
Dusty Bradford
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The turbo throws this situation off.
The same converter will stall higher on the stroker motor than it will on the stock motor........IF both have the 67mm turbo.
The stock turbo is very small so it comes into boost more quickly than the 67mm. So on a stock motor, stock turbo combo you could see a very similiar stall with the same converter as you would on a stroker 67mm combo.
TurboTnZ06
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That makes sense, but I keep thinking 0 boost on a 9 sec engine would have considerably more horsepower than a stocker at 0 boost, which would be able to spin the converter to a higher rpm, if that difference was considerable, maybe its only 20hp. After all, this is a pretty much unrealistic comparison anyways, as the goal is not to launch at 0 psi, but as high as possible and the rpm is whatever it is. I run a 3000 stall 9/11 pts with a TE45a and gain 27-28 mph on the big end 1/8-1/4 with it unlocked on the old 231 inch iron head setup, however it could only do 1.65 60 foots off the footbrake as it wouldn't build more boost at the line. I probably need more converter, but with the new stroker I think I'll see how it does and then reconsider a new flash when the trans comes out for a freshening. Thanks for your info.
