flash rpm question

[al wisniewski]

Given a specific flash rpm,if torque and hp are increased,what is the typical flash rpm the convertor will see? Thanks.

[Billy Nees]

I'm not sure that I'm understanding your question.
BUT, if you have a combo that has a known "flash RPM" and you increase the torque and HP, your "flash RPM" should increase.

[ss3011]

K=R/square root of T

K is the constant Factor of the converter and will stay the same
T is torque
R is the stall speed

So by combining old torque equation and new torque equation , knowing K is constant

Rnew = Rold x (SqRt Tnew / SqRt Told)

Example
Rold = 5000 rpm
Told = 500 ft.lbs.
Tnew = 550 ft.lbs.

Rnew = 5000 x (sqrt 550 / sqrt 500)
Rnew = 5000 x (23.45 / 22.36)
Rnew = 5000 x (1.0488)
Rnew = 5244

So basically with this converter if you upped the torque by 50 ft.lbs , it would increase the stall from 5000 rpm to 5244 rpm .

[Billy Nees]

^^^^^^^^^^and he would know!^^^^^^^^^^^^

[al wisniewski]

Billy,I know it will increase,just trying to get a feel for what I will have and figuring a new convertor out.

[al wisniewski]

SS3011,thanks for the formula!

[340Cuda]

Do any converter manufactures show a "K" rating for their converters?

I only remember Mopar Performance doing that in the past.

[Ed Wright]

Originally Posted by ss3011

K=R/square root of T

K is the constant Factor of the converter and will stay the same
T is torque
R is the stall speed

So by combining old torque equation and new torque equation , knowing K is constant

Rnew = Rold x (SqRt Tnew / SqRt Told)

Example
Rold = 5000 rpm
Told = 500 ft.lbs.
Tnew = 550 ft.lbs.

Rnew = 5000 x (sqrt 550 / sqrt 500)
Rnew = 5000 x (23.45 / 22.36)
Rnew = 5000 x (1.0488)
Rnew = 5244

So basically with this converter if you upped the torque by 50 ft.lbs , it would increase the stall from 5000 rpm to 5244 rpm .

Very interesting. Thank you!

[FED 387]

If k is the constant factor of the converter is that factor the same for all converters or does each converter have its own specific factor? How is the factor determined? Thanx very informative where did you obtain this formula? FED 387

[ss3011]

The K factor is specific for each converter . We had a converter dyno that we would lock the output shaft (stall) and then input a specific torque , then we would measure the rpm . The formula K = R / sqrt T was developed from those tests . As long as the converter is not cavitating that formula will hold true .


If you have a transbrake and a dyno torque curve on your engine , you can determine the K factor of your converter . You would just engage the transbrake , go WOT (no two step) and measure the rpm your engine goes to . Then you can look up on your torque curve what engine torque you achieved at that RPM . Plug the numbers into the formula , to determine the K factor . This is a great way to determine the relative difference in looseness between different converters .