Our ability to reprogram the ECU (engine management
computer) for the SVX let's us retune the car for
performance and for performance enhancements. The memory
adaptor we've developed holds two versions of software and
is able to switch between them on the fly. This was
designed into the hardware
to allow tuning for multiple fuels or a large shot of nitrous oxide.
The Stage One SVX package offers the Stage 1 performance
code in the first location and a variant of that code to run
87 octane or nitrous oxide in the second memory location. A simple spst switch
can be used to switch between the two versions at fill up.
When a nitrous oxide system is installed the memory adaptor
can be wired to the nitrous oxide system and will switch
automatically when the solenoids are activated. We've been developing the software for Stage One specifically to meet
the desires of SVX owners as voiced in the forums at
The SVX World
Network. Particular concerns addressed were
acceleration, power, fuel economy, and with the increasing
popularity of manual transmission swaps the rev limiter.
With the Stage 1 software serious improvements have been
made in all of these areas.
We've determined
the US market Subaru SVX runs a relatively lean air to
fuel ratio. Measurements with a wide band
gas analyzer on a dynometer showed the AFR on our test
vehicle to be between 15.0 to 1 and 13.5 to 1 with the
leanest areas being at low rpm's. Since best performance is
generally obtained from an AFR between 12.5 and 12.9 to 1, the logical
conclusion seems to be that Subaru detuned the US
market SVX with a leaner AFR in order to meet the
extremely stringent emissions requirements put on original
equipment manufacturers. A particular problem
with this lean of an air to fuel ratio is that it makes the 10.0 to 1 compression
engine prone to knock--the precursor to detonation.
The tendency to knock is worsened when compounded with
atmospheric conditions which result in a throttle enrichment
that further leans the air to fuel ratio under heavy
acceleration from a stop or low RPMs. While the dual knock
sensors and ignition timing retard system are able to
prevent knock by retarding ignition timing advance the
resulting reduction in ignition timing reduces performance.
In the Stage One code adjustments were made to the fuel map
to keep the air to fuel ratio between 12.5 and 12.9 to 1
when accelerating . This removed the intermittent hesitation found
during heavy throttle from a stop or low RPMs and greatly
improved part throttle, every day driving performance .
With this fuel map we were also able to utilize more
ignition advance for further torque gains.
Once we removed the knock causing lean
condition we were able to create a second set of code with
an ignition advance table which runs well with 87 octane
regular unleaded. The code optimized for 87 octane
regular unleaded is loaded into the second memory location
of the memory adaptor for Stage One. At fill up the
user can switch to the appropriate version of code to match
the fuel used via a simple "spst" switch. If
the user wishes to install a nitrous oxide system for drag
racing the memory adaptor can be wired to the nitrous oxide
system and the second version of software will help prevent
detonation.
With it becoming more and more common to swap a manual
gearbox into an SVX it is obvious that it would be
advantageous to have a higher rev limit than the factory
6600-6700 rpm limit. We raised the rev limit in all
our software versions to 7400 RPMs; adjustments were also
made to the lower RPM portions of the ignition table to
improve performance with a manual transmission.
Subaru SVX Stage One FAQ
Subaru SVX Stage One Photos
Subaru SVX Stage I installation Instructions
SVX Stage One is
only available for the OBDI Subaru SVX; 1992 through
1995 model years are OBDI. SVX's with OBDII ECU's,
model years 96 & 97, will not accept the memory
adaptor used for SVX Stage One. SVX Stage One
ships with the wire to connect to a spst switch, a grommet
for running the wire out of the ecu, fender badges, and an 8 page
instruction manual. |
