The most advanced plug-and-play tuning system for the 2.4L turbo Subaru — up to 50 whp (70 hp crank) on a completely stock car, with no flash and no risk to your factory ECU.
Real Power, No Flash Required
The JB4 is the most advanced plug-and-play tuning system available for the Subaru 2.4L turbo platform. Power gains of up to 50 horsepower to the wheels (70 hp crank) are possible on a completely stock car running pump gas. Add bolt-ons, higher octane, or E85 mixtures and the gains climb even higher.
Unlike a flash tune, the JB4 needs no staged upgrades or supporting mods — install it as your very first upgrade and immediately feel stronger acceleration, faster turbo response, and smoother power delivery. And because it never touches your ECU, you get safe, significant gains while keeping every factory safety system.
JB4 PRO Bluetooth — Included
The all-new JB4 PRO adapter fits fully inside the JB4 enclosure for weather protection and a clean look, and wirelessly connects to your iOS or Android device. Record and analyze data, switch performance maps on the fly, and pull free firmware updates as BMS releases more powerful maps and new features.
The JB4PRO Free app adds an intuitive interface, help buttons, and advanced log-analysis tools that estimate performance and flag any tuning concerns.
Advanced Tuning, Built In
Dyno Results — Stock vs. JB4
2022+ Subaru WRX 2.4L turbo — factory tuning vs. JB4. Click to enlarge.
Easy Plug-and-Play Install
The JB4 harness plugs into accessible engine-bay connectors — fast to install, fast to remove, and completely reversible. Watch the full WRX install, then grab the WRX install guide (PDF).
A Decade of Proven Tuning
The JB4 has been the gold standard in plug-and-play turbocharged tuning for over a decade, sold in 67+ countries. It installs between your car's sensors and the ECU and safely manipulates boost, timing, and fueling for real gains — with full CANbus integration, fuel & spark control, and Bluetooth logging no other piggyback can match. Not VIN-locked, so you can remove it, swap it between cars, or resell it later.
🔧 Vehicle Fitment
2022+ Subaru WRX • 2019+ Subaru Ascent • 2020+ Subaru Legacy XT • 2020+ Subaru Outback XT — all with the 2.4L 4-cylinder turbo.
FAQ
Which Subarus does this fit? 2022+ WRX, 2019+ Ascent, and 2020+ Legacy XT / Outback XT with the 2.4L turbo.
Do I need to flash my ECU? No. The JB4 requires no ECU flash — real gains without unlocking or flagging your ECU.
How much power will I gain? Up to 50 whp (70 hp crank) on a stock car on pump gas, with more available on higher octane, E85, or with bolt-ons.
Does it have Bluetooth? Yes — the included JB4 PRO adapter and free app connect wirelessly for map switching, logging, and firmware updates.
What octane do I need? 91 octane or better is required for the performance gains. E85 blends unlock the more aggressive maps.
Is it reversible? Completely. The JB4 is not VIN-locked — remove it any time, swap it between vehicles, or resell it later.
