this converter is already on my car and have lost mph in the 1/4 but the shop that built it swears it's waaay more efficient than the stock converter. is there any way for me to tell or am i at thier mercy when it comes to this? They also say it has an STR of 2.4 but it doesn't feel like it to me since it is supposedly a 2400 converter which i can brake stall to 2600.
so is there any way to figure these things out while the converter is on the car? possibly with a dyno? i dont have dyno numbers from the stock converter so i wont be able to measure how much hp i lost . if anybody knows anything feel free to chime in
-Joe

I dont think that there is anyway to figure out the efficeincy.... What kind of converter is it? Do you know what its made of? If you cant answer those two questions Id advise you to change it. It might last 80,000 miles or it might last till next week... Good luck

First off, STR can only be measured with a test bench - ie. an engine with a 100% known torque curve, and output shaft dyno to measure what's coming out. It's also going to vary a bit based on your input torque, just like stall speed will.. Efficiency -- at what RPM? At what torque level? This one REALLY won't be a constant number, with a ton of variables. What's the best way to pick the right converter? See what works in real-world cars

I've seen the efficiency comparo on Yank's site
where a good many of their converters are shown
as better-than-OEM efficiency. But, it baffles me
why GM would have both low stall and inefficient
operation, especially since of all the converter
vendors (theirs comes bundled with a car) GM is
the only one on the hook for CAFE.

No hype exists in the automotive aftermarket.
Say it with me, now.

I expect that only an independent test,
untainted by marketing interests, would be
entirely believable. And of course we all have
the time and dough for that.

This may not be at all what you're looking for but hey...

You can very easily compute the ideal relationship between vehicle speed and engine speed, making some assumptions about tire sizes, gear ratios, and no loss through drivetrain components. (You can verify your model by looking at ODB-II data collected under TCC lockup conditions.) You can then easily collect OBD-II data under other conditions (varying rate of acceleration, vehicle weight, ...) and compare this to the ideal. If you did this before and after your swap you could definitely tell which is closer to ideal and how that varied as a function of RPM, TPS, etc. This does lump all the sources of loss into the same bucket though and won't isolate the converter.

None of this probably helps you identify your converter which is what I think you're really after.

Real world efficency can be measured 2 ways:

1) After couple-up (not lock-up) by the ratio of input shaft speed (same as engine rpm) to output shaft speed (available in ATAP). This will give you the rpm slip and you can calculate a percentage.

2) Dyno the car with the converter locked and unlocked. This will show your torque multiplication at low rpms and converter HP loss at the top end.

On a converter dyno, generally a standard torque input is used to allow comparison accross converters.

thats what i was looking for

Keep in mind this includes any source of loss between input and output, not just the converter. Close enough for government work though. ISS is always proportional to OSS as far as the PCM is concerned, I think Joel is suggesting something like this:

"efficiency" = 100 * (engine speed - TCC slip speed) / (engine speed)

Of course on decel, that's greater than 1, so maybe it should be absolute value of slip.

I'm chicken and hate dynoing with the TCC locked. Might also be useful to command specific gear for this (for low RPM stuff)?