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transmission control unit or TCU is the computer which
controls the transmission's operation. These TCU's
have been socketed to accept JDEC standard 28 pin DIP memory
devices to allow updating of the software and come with new
ECUtune shift maps. They are ready to plug in and run
on any SVX with ECUtune engine management software or even
on an SVX with stock engine management if raised rev limits
are not desired. One of the ECUtune adjustments made was
to lower the trigger temperature for the ATF temperature
warning light to come on at 100°C
(212°F). It will shut back off when the ATF
temperature drops below 95°C (203°F). This was done
mainly because the 4EAT transmission used in the SVX
overheats badly when overfilled with fluid--a mistake many
owners make because the dipstick is notoriously hard to
read. A warning light at 212°F should alert such an
owner to his/her mistake in time to save the transmission.
The thresholds for the overheat mode have been reduced to the
same temperatures so that the transmission control unit
begins taking steps to reduce ATF temp (such as locking the
torque converter and changing the shift maps used) at the
same time it warns the driver.
The shift maps dictate
when to up-shift or down-shift from the current gear based
on throttle input and vehicle speed. The ECUtune maps down-shift
to first gear with less throttle and generally hold gears
longer with moderate throttle so it is not necessary to
floor the gas to get it to go (ECUtune
1-2 and 2-1 shift maps). This gives the car a
much sportier feel around town while greatly improving fuel
economy because less throttle is needed to attain desired
performance. The full throttle up-shifts in the
ECUtune shift maps are all set to speeds which are
equivalent to 7800 RPMs (with 3.545 gearing); however, the
actual rpm of the full throttle shift is adjusted through
the rev. limit for each gear. This allows us to
easily customize the full throttle shift points of each gear
to any desired RPM of 7800 or less. If no preference
is specified when ordering the TCU will ship with the O.E.
rev. limits = the O.E. full throttle shift points of about
6500 RPM in all gears. To request custom rev. limits just
enter notes with your order in Paypal. You can specify
any rev. limit up to 7800 RPM for each up-shift. You
can also specify different rev. limits for each upshift in
manual mode.
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