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Civic Si ECU flash tune
Your Civic Si
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+20–35 whp (est.)
Easy$600–$80030–60 min
Why do it
The biggest gain for the money on this car. Hondata says its Sport mode map alone adds about 27 hp and 40 lb-ft on a stock Si.
Tools you'll need
- Tuning device
- Battery charger to keep voltage steady
Parts to buy
- Hondata FlashPro (2017–2021 Civic Si) Full tuning and datalogging. Sold for competition use.Fits 2017–2020
- Hondata CARB FlashPro 50-state emissions legal version with fewer tuning features.Fits 2017–2020
Doesn't fit your car (0)
Always double-check fitment for your exact year, trim and transmission before buying. Prices change. ModBuddy doesn't earn money from these links.
Steps
- Connect a battery charger.
- Plug the tuning device into the OBD-II port.
- Save your stock ECU file first.
- Flash the tune that matches your parts and fuel, without interrupting it.
- Drive gently at first and follow the tuner's instructions.
Safety first
- Park on flat, solid ground, set the parking brake and chock the wheels.
- Use jack stands rated for your car. Never get under a car held up only by a jack.
- Let the engine and exhaust cool completely before touching them.
- Disconnect the negative battery terminal before unplugging sensors or electrical parts.
- Wear safety glasses, and gloves around sharp heat shields and hot fluids.
- Tighten bolts to the torque spec in your factory service manual.
- If a step doesn't match your car or you're unsure, stop and ask a shop.
These are overview steps written to help you plan the job. Always follow the instructions that come with your part and the procedures and torque specs in your factory service manual. Horsepower is an estimate; results vary.