Evo X / RA - SST Upshift Patch

Most Big Turbo SST-equipped Evo X's share the same problem, on an upshift, the turbo is still spinning at the pre-shift speed, so the car overboosts by a few PSI post shift. The factory ECU has no fast mechanism to catch this, and the result is a boost spike, a harsh torque hit through the freshly-engaged clutch, and unnecessary strain on the gearbox. This patch adds a proper upshift torque-management strategy to the factory ECU. The moment a shift begins, it smoothly pulls a tunable amount of ignition timing and wastegate duty, holds that reduction through the gear engagement and the critical post-shift window where the overboost lives, then ramps everything back to normal. The result is a flatter boost trace across shifts and a noticeably smoother transition into each gear.

How it works

• The patch detects when the car is upshifting using CAN requests from the gearbox. During the clutch engagement phase, the tunable reductions activate.
• Two tunable tables are provided to set the reduction: one for ignition timing (degrees) and one for wastegate duty (%). The timing reduction acts on the final commanded timing after all factory logic; the wastegate reduction acts on the final solenoid duty after the factory closed-loop correction, so closed loop boost control can't fight the requested reduction.
• The patch knows exactly when the next gear has engaged. From that point it holds full reduction for a tunable time (the overboost window), then ramps the reduction back to zero linearly over a second tunable period. Edge cases like accidental back-to-back shifts are handled — the reduction never drops out between gears.

Everything is tunable in EcuFlash (enable switch, activation thresholds, hold time, ramp time, both tables, and a minimum-timing safety clamp), and a full EvoScan datalog set is included so you can watch the patch state, the live reductions, and the boost trace in real time.

Benifits

• Kills the post-upshift boost spike at the source instead of having to compromise on wastegate targets during tuning.
• Smoother, softer gear transitions — torque is reduced through the clutch handover and reintroduced progressively, not dumped back in
• Less shock load on the SST clutches and drivetrain on every full-throttle shift
• Fully active at wide-open throttle, where factory torque reduction is disabled.
• Completely tunable per setup — from a barely-noticeable trim on a stock car to aggressive reductions on built setups.

Requirements

• A TC-SST Equipped Evo X or Ralliart running TephraXMod V3
• EcuFlash + a Tactrix Openport cable for installation and tuning
• A 3/4port boost solenoid running on the active wastegate wiring - this patch does not support factory boost solenoids.
• EvoScan (or similar) recommended for calibration datalogging

Warnings

• For off-road / motorsport use only. This patch modifies ignition timing and boost control behaviour.
• Requires calibration. The shipped defaults are deliberately conservative, but every car (turbo, clutch calibration, tune) is different. Start with the wastegate table zeroed and a small timing reduction, confirm correct operation in a datalog, then tune up. Do not simply install and send it.
• Tuner-level modification. You should be comfortable reading boost/timing logs and understand what pulling timing and wastegate duty does before changing the tables.
• The timing reduction is applied after the factory safety clips. A tunable minimum-timing clamp is built in (default matches the factory floor) — do not lower it without understanding the exhaust-temperature consequences of large retard under load.