STI GD — Stage 2 ECU Tune
- 52% increase in power output
- 26% increase in torque delivery
- Improved fuel efficiency
- Enhanced boost control via Haltech management
- Optimized fuel mapping for E85 compatibility
- Better engine responsiveness and drivability
This 2004 GD STI runs a 2.1 closed deck stroker with Haltech management, built for off-road and closed-circuit competition. The platform supports E85 on 1.38 bar through a Blouch 1.5 turbo, equal length headers, water to air intercooler, and mild cams. Peak output sits at 164 kW at the wheels, up 56 kW from the factory 108, with torque lifting from 239 to 301 Nm.
The closed deck block and high pressure pump provide headroom for E85 delivery under sustained load. Haltech calibration allows direct management of the wastegate solenoid and fuelling strategy, keeping the EJ20 safe at this boost level. The file balances response and top-end while respecting the stroker's thermal limits on track.
Why Haltech for this build instead of reflashing the factory ECU?
At this level—stroker motor, E85, 1.38 bar boost—a standalone gives proper control over fuelling, ignition mapping, and boost management. The factory ECU can't handle the larger displacement or fuel type safely.
Is 164 kW conservative for a 2.1 stroker on E85?
Yes, but longevity matters on a closed deck track build. The tune prioritises safe AFRs and timing under sustained load rather than chasing peak numbers that won't hold over a session.
What's the advantage of equal length headers on this setup?
Equal length headers smooth out exhaust pulses, reducing the classic EJ rumble but improving spool consistency and making boost control more predictable at the wastegate.
Workshop & Dealer Access
Protunes supplies ECU calibration files exclusively to approved workshops, tuners, and dealers throughout Australia. Platform: Haltech.
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