11/11/2003

Overdriving Your Torque Convertor

Reading Modern Transmission Systems by A.W. Judge - printing by the same
people that printed Dykes and the Motor Manuals before going down to the
general automotive stupidity of the current generation of what wants to
claim to be mechanics.

Dealing with hydro-kinetic converters and gear trains.  

Simple little fact to keep in mind.  The power available to the entire
downstream gear train with the convertor not above stall speed is
limited to a maximum of the power available at converter stall.  Gears
only change the relationship of torque to rpm - they are still limited
to the max power at stall.

So what would happen if you put a gear upstream of the TQ?  In other
words - between the engine and the convertor instead of after it?

Well, if this gear ratio was about 1.6 to 1, it would raise the stall
speed by about 100%.  And, since the TQ was turning a lot slower, it
would effectively weigh a whole lot less and have much less limiting
effect on acceleration.

Assume the 1:1 lock up is 2000 rpm - not particularly unreasonable.
This is the maximum power that the engine can move below this range.
Above this rpm, there is no effect of the TQ except some coupling slip -
a locked tq would be more effective.  No torque multiplication or
anything.  

Now we put in the 1.6 to one.  This effectively increases the stall
speed to about 4000 rpm at the engine.  Anyone not believe there is
seriously more power available at 4 grand than at 2?    Oh and by the
way, the range for torque multiplication is increased by the same
percentage - so the engine does not have to be near as torquey with this
gearing as it would with straight 1:1.

Looking at other data, appears the worse case slippage and loss -
emphasis worst case - for automatic transmissions appears to be around
12.5% at full load under the worst possible situations.  

Would go into the use of differential drives with split direct and
hydraulic coupling - but I am still having fun learning things and I
don't need to be told it wont work yet.  

But on this gear ahead of TQ instead of behind, A two speed unit
provides about the same torque characteristics as a four speed
conventional unit.  Oh well.

And I guess the full description and layout of how a Chevrolet
TurboGlide transmission functions would not be of interest.

Have to find and buy a later edition - hopefully it will cover a
dual-path transmission.   That would be nice.