15
G. TRANSMISSION SHIFT POINT MPH & RPM
(AUTOMATICS ONLY)
Be sure to read and understand this entire section before
attempting to reprogram your shift points.
The shift point option allows you to change the RPM at which
your transmission shifts at wide-open throttle, to find the very best
shift points for maximum acceleration. You can
try
optimizing
the shift points using the seat-of-your-pants technique, but how
will you know if your e.t.’s improved? The only accurate method
for this optimization is at the track with timing slips as the
measuring device.
In order to optimize the performance of any vehicle, consistent
test results are necessary.
If a vehicle varies plus or minus
1/10th of a second in the quarter-mile, run to run, with
no
changes, it is impossible to test any product (shift point, starting
line RPM, etc.) that has the potential to gain 1/10th or 2/10ths of
a second, because the gains or losses on any one (1) run could be
due to inconsistency rather than the variable being tested.
Therefore, before testing
anything,
make the vehicle consistent.
Wheel-spin, if present, is the overwhelming cause of incon-
sistency
. You
must
develop a starting-line technique that gives
you the best repeatable elapsed times. Tires are the most impor-
tant product you need to cure wheel-spin. For street-driven
vehicles, we recommend D.O.T. approved street slicks as large
as you can fit under the wheel wells of your vehicle. In any case,
before testing shift points, arrive at the starting line technique that
gives you the best repeatable results, with or without slicks.
Throw out
any
run with excessive wheel-spin, and try to get
at least three (3) runs that repeat within 4 or 5 hundredths of a
second. Then average them and
use this average value (not just
your best run) for all testing comparisons
. Your best e.t.’s will
occur when you leave as hard as you can without wheel-spin.
Confirm this by practicing and observing the results.
And finally, a very important point for any and all high-
performance testing: always test only one (1) variable at a
time until it is optimized.
For shift point optimization, this
means test only one (1) shift point at a time until the best RPM is
found, leaving all other shift points alone. Once the best 1-2 shift
point is found, program it in and leave it. Then repeat the same
optimization procedure for the 2-3 shift point.