Response comes first
The move to a smaller turbo put the driving experience ahead of chasing a bigger peak number. Response and usable power were central to the direction of this build.
FEATURED BUILD / LUCAS / 2018 SUBARU STI
The ultimate
GT STI.
My description of Lucas’s STI: a standout grand-touring build, with a documented development history leading to Emtron engine management and separate pump-gas and ethanol calibrations.
Plan your build ↗2018 STILucas’s Subaru
EmtronJanuary 2025 tuning stage
564.5 hpE80 report · January 6, 2025
PROJECT PHOTO GALLERY
Lucas’s 2018 STI
The car on the rollers, its engine bay and a workshop view from AWD Tuning’s September 2023 archive. These photos predate the later Emtron development chapter.
Original photos: AWD Tuning · September 2023. Select a photo to open the larger image.
More project galleries →THE COMPLETE CAR
More than a peak-power number.
I think of Lucas’s STI as my “ultimate GT STI”. That is my personal assessment of the overall build: a car that belongs in my history alongside the competition cars, while representing a different goal for the finished package.
The dyno archive identifies the vehicle as a 2018 Subaru STI and Lucas as the owner. Its later reports document Emtron flex-fuel tuning. We moved to a smaller turbo to improve response and the overall driving experience.
Documented build details
- Vehicle: 2018 Subaru STI
- Owner: Lucas
- Tuning: Keith Fields, during his AWD Tuning work
- Engine: AWD 770 / Rallispec long-block
- Camshafts: Kelford 264s
- 2025 turbo: ETS rotated kit with BorgWarner EFR 7670
- Fuel system: AWD fuel system
- Driver control: three SI-Drive power modes
- Later ECU platform: Emtron
- 2025 fuel labels: 93 octane and E80
- Dyno: Mustang Dynamometer
The 2025 hardware is documented in AWD’s January 15 Instagram feature, which I confirm shows Lucas’s car. Exact ECU model, boost pressure and complete internal specifications are not stated.
WATCH THE BUILD / JANUARY 15, 2025
560-plus at the wheels.
Three ways to drive it.
AWD’s video documents the Rallispec long-block, Kelford cams and rotated EFR 7670 combination. Its caption explains that the SI-Drive selector controls three distinct power experiences, with smooth drivability remaining a priority. That is the detail behind my GT description: the calibration considers how the driver uses the car, as well as what it produces on the dyno.
The tuning brief
Preserve a smooth driving experience while giving the owner distinct levels of performance through the factory selector.
The post reports more than 560 horsepower at the wheels. The dated E80 report supplies the more precise 564.5 hp / 550.2 lb-ft result. These sources document the same build chapter, while the original report remains the reference for its test date and maxima.
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The owner’s road report.
On February 1, 2025, Lucas shared the car after AWD Tuning’s finishing work. He identified the new Rallispec engine and Emtron ECU, reported a trouble-free 700-mile drive home, and praised the smooth ride. It is a useful owner account of the finished car’s road manners alongside the dyno record.
Read Lucas’s original build update ↗
JANUARY 2025 / EMTRON STAGE
Two fuels. Two documented sessions.
The individual reports record the following maximum power and torque figures. Fuel and ECU descriptions come from their archive filenames; the dates and maxima come from the report text.
| Run date | Fuel label | Power | Torque |
|---|---|---|---|
| January 5, 2025 | 93 octane | 475.6 hp @ 6,590 rpm | 452.7 lb-ft @ 4,562 rpm |
| January 6, 2025 | E80 | 564.5 hp @ 6,336 rpm | 550.2 lb-ft @ 4,492 rpm |
Both reports were printed January 10, 2025 and indicate weather correction (WCF). These are historical results for Lucas’s car, not guaranteed outputs for another STI. Separate sessions should not be treated as a controlled fuel-only comparison.
THE DEVELOPMENT RECORD
A build with history.
2022 runs · Reprinted in 2023
Other reports preserve a July 10 run at 418.6 hp / 381.1 lb-ft and a July 19 run at 548.5 hp / 460.5 lb-ft. Their filenames identify 93 octane and E85 respectively. Both were printed in May 2023, illustrating why export dates are not tuning dates.
2025 · Emtron chapter
The January reports document the Emtron stage on 93 octane and E80. This is the stage behind my description of the finished STI as a grand-touring build.
How this history is documented
This feature uses my firsthand account and Lucas’s original reports from the AWD dyno archive. The reports identify Lucas by name and the car by year, make and model. Customer registration details are omitted from this page.
Dyno report references
- lucas 2018 STI AP EMtron FF 93 oct ActiveReports Document.pdf — tested January 5, 2025; printed January 10, 2025.
- lucas 2018 STI AP EMtron FF e80 ActiveReports Document.pdf — tested January 6, 2025; printed January 10, 2025.
- Lucas 2018 STI AP 93oct ActiveReports Document.pdf — tested July 10, 2022; printed May 24, 2023.
- Lucas 2018 STI AP e85 ActiveReports Document.pdf — tested July 19, 2022; printed May 24, 2023.
Build your STI around how you drive.
Discuss the complete combination with me: available fuel, hardware, engine management and what you want from the car. My work spans factory-ECU tuning and standalone systems, backed by standard and advanced Emtron training through EFI University.