Science behind building a converter

[Chris Hill]

Mark,


Are there any general converter fundamental governing equations?


Folks always talk about flash rpm and lock-up, but what happens to torque multiplication when flash rpm is "adjusted"?


Also, what happens if fluid viscosity changes?

[Mark Yacavone]

Chris ,There are some formulas but they are very complex.I certainly can't understand them but you just might.
I found something that might be easier to comprehend for most here:

http://www.sonnax.com/articles/90-Hi...ction-and-More

On the second part, the best non answer I can give is it might get better or it might get worse.
Generally when you soften one up by machining stators away from factory engineered profiles, you do lose a few % points of torque multiplication . But if it gets you up where there is more torque to multiply at a certain rpm, then you still will have a net gain in ET.

Personally,I haven't seen any big swing in brake stall within what one would call normal drag racing temperature ranges. Once we get to the point where the fluid starts to boil and vaporize, then we will see a loss in 60' times for sure.
I'm assuming you were asking about temperatures, seeing that most folks use one form of 10w ATF or another.
If you're asking about synthenics in converters, I have no experience.
Some else will have to field that one.

[Chris Hill]

Mark,


Thank you! Now trying to wrap my head around the info.


With factory designs, if stall torque ratio (STR) increases, does converter lock-up efficiency increase, decrease, or stay the same?


Do they have converter dynos?


And the guide listed to determine correct converter does not work well for engines that have a wide spread for peak torque rpm and peak hp rpm.

[ss3011]

A good formula to know is K=R/(square root T) R is RPM T is Torque The way this formula works is each converter has a "K" factor, which classifies the converter. This number is usually figured at stall, or no output . So if K is a constant, you can figure the stall speed at various Torques. As long as a converter is not cavitating the K is constant.

example: if the converter has a K of 250 and T = 400 ft lbs then R will = 5000 rpm change the T to 500 ft lbs and R will be 5590 rpm.

K factors are usually figured out by testing on a converter dyno, but if you have a very accurate engine torque curve you can figure it out by doing a WOT stall using a transbrake to figure out the WOT rpm, then plugging the numbers into the above formula.

[Ultimate Converter Concepts]

http://www.ultimateconverter.com/tor...or-drag-racing

Kind of a long read, but helpful

[HP HUNTER]

I can only speak for foot brake type converters, the type of core (case) is very important as well as the weight, and then testing testing and testing, I don't really care about slip, but I do care about the time slip. 1320 divided by MPH is a good start.

[west coast]

This is all good, starting to understand some of the stuff that effects other stuff on my car and others. Keep it coming. Thanks for pointing to some of this info.