STI MY18 — Stage 2 ECU Tune
- 5% power increase to 176kW
- 14% torque increase to 353Nm
- Improved boost control
- Enhanced fuel delivery system
- Drive by wire optimization
- Maintained reliability with bolt-on modifications
This MY18 STI came through on 98 RON with a typical Stage 2 bolt-on package: intake, downpipe, catback, upgraded injectors, high-pressure fuel pump, and boost solenoids. The goal was to extract usable midrange torque without chasing headline figures or stressing the EJ25 platform.
Factory ECU responded well to the hardware. Torque lifted from 309 Nm to 353 Nm at the wheels, with power climbing from 168 kW to 176 kW. The curve is noticeably fatter through third and fourth, which is where these cars live on tighter roads and shorter on-ramps.
Fuel and timing maps were opened up to match the freer-flowing exhaust and improved fuel delivery. No drama, no boost spikes. A sensible step for an STI that still sees regular street use.
Why the modest power gain on a Stage 2 STI?
The EJ25 platform in the MY18 STI is conservative from factory and responds better in torque than peak power without a turbo upgrade. This tune prioritises drivability and reliability over chasing big numbers.
Does this tune require ongoing octane discipline?
Yes. The calibration is written for 98 RON minimum. Anything less will cause the ECU to pull timing and you'll lose the midrange torque gains that make this tune worthwhile.
Can this file be adapted for a similar MY15–17 STI?
Not directly. The MY18 factory ECU has different base maps and hardware calibration. Each model year needs its own base file even with identical bolt-ons.
Workshop & Dealer Access
Protunes supplies ECU calibration files exclusively to approved workshops, tuners, and dealers throughout Australia. Platform: Factory.
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