Technical > Dan Dishon's Transmission Den

Effects of Loosening the Converter Stall

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jspell:
Does loosening the converter take away top end mph? 

ricardo1967:
Not... IF the extra converter stall speed is accompanied by engine revving strong at proportionally higher RPM.

Example: if you currently have too much cam/head for a given converter, a looser converter will help.

The win-win is a lockup converter (which acts like a third gear on a glide), but that's so expensive.

dusterdave173:
Interesting..OK..Question
My combo is 350,domes, small heads 195cc runner, small roller 255/260 .590 lift
I do not have a tach --have a mystery 8 inch converter that seems crazy loose but seems to work perfect
Car does not drop much rpm at all on gear change 
based on my et 5.62 in 1/8th is my MPH of 122 good or bad? 60 ft average 1.21
I feel like combo is working good but wonder what to change to get car faster.
I have another shortblock same compression with bigger roller 275/280 .650 lift and plan better heads
but will be using same Hilborn that is 2 3/16ths not the bigger 2 7/16ths so many use
Thanks

jspell:
My converter is from a nationally known manufacturer but when u speak with them they are half listening to your combination.  No matter what combo I have I feel like they give you the same part number off the shelf.

bikeguy307:
Good question,

Converters are a simple but yet complex piece of a race cars combination, and getting it right is important to having a consistent race car.

There is a difference between "loosening" a converter and raising the stall speed, you can build 2 converters that will stall the same behind the same motor, but have different slip ratio's. The fin angle is the main factor in a converters efficiency. So by changing the fin angle in a negative direction to raise stall speed you also loosen the converter, and raise the slip ratio. You can over come some of the higher slip ratio by reving the engine higher as Ricardo stated. but you will never get what you had before the fin angle change.

Now we get to the stator, changing the stator can move stall speed as much a 800rpm in either direction depending where you are at now. The angle and number of window in the stator can change stall without changing the fin angle there for having much less effect on the slip ratio. The stator is key to torque multiplication.

So depending on how the converter is "loosened" depends how it will effect you top end speed.

 
So what combination is right for your car? That's the million dollar question. Having a good converter guy is very important in the processes, buying off the shelf from a parts store (Jegs, Summit) will get you close. Having a converter spec built is the best way, but you really need good data to give them to get it right. So it's always better to deal with the converter companies directly.

Dave,

That is pretty good mph for that ET, I run low 70s high 60s with my Roadster at 118mph. I run a soft loose converter for a reason, some of the tracks we race on are not the best prepped, so having a soft converter helps keep the 60 ft consistent on a loose track, this is one of many factors to consider when getting a converter. 


Hope this helps, and feel free to call me if you would like to talk further in detail, promise I won't try to sell you a converter, just give you a little more insight in to what to ask for with your current guy.

Dan 574-722-5915.

   

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