Torque Converter Lock-Ups

[Roger Heflin]

I have the flowchart for computer control of the TCC for a 93 Z28
posted on my web site.  I was able to determine what most of it was
doing.  The computer seems to start thinking about locking it at 50mph
(any gear possible).  If the throttle is below a certain limit (the
limit is determined by rpm) than it locks it.   It also has a setup to
lock the convertor at 95 mph reguardless of throttle position, gear,
or anything, It will lock the convertor at WOT in 3rd gear.  There is
also some code to unlock the convertor during downshifts, and a
counter to keep it unlocked long enough for the shift to finish.
There is also some code to do some things with the TCC while coasting.

The flowchart is at:

http://www.hit.net/~rah/EDD3_EF37.gif

You will need to ignore alot of the first stuff in the flowchart, it
appears there is some code to lockup the convertor to reduce noise,
but it appears to be disabled in the bin I have.  It seems to want to
lock the convertor for a certain time period and then unlock it.

			Roger

On Wed, 30 Dec 1998, Greg Hermann wrote:

> >There are no iron clad strategies, for TCC.  What some one says is usually
> >about their experience.
> 
> 
> Just some food for thought:
> 
> Allison has been using lock-up torque converters for decades--since well
> before the invention of the integrated circuit, probably since before the
> invention of the transistor. And, obviously in some VERY heavy duty stuff.
> 
> Most of their hydraulically controlled units (virtually anything prior to
> 1990) engage the converter lock-up clutch when a certain (rather low) road
> speed is reached in either the first or second gear used when starting from
> rest, and then only "tap" the lock-up clutch during actual shifts (in
> hydraulic control models, the valve which does this is actuated by the flow
> of fluid involved in applying the clutch for the next gear.)
> 
> No brake light circuit interlocks, or anything else like that were used on
> the hydraulic control models..
> 
> And their converters can be disassembled. Interchange of parts usually
> allows setting up the converter to give a torque multiple ratio anywhere
> from 1.8 on up to 3.5:1. (By Factory Design)
> 
> I haven't really looked at it in detail, but I doubt that the line pressure
> in any automatic transmission at idle  speed and throttle position (or
> vacuum level) is high enough to achieve a "launch" into an intersection
> anyway. (And I think that all would agree that a Cummins 855 would put a
> bit more impetus into any such launch than a Chevy!!)
> 
> Not to say that there is anything wrong with wearing a belt AND suspenders!
> 
> Regards, Greg
> 
> 
>