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Case study ยท Boost control hardware and firmware
An electronic wastegate the factory Honda ECU commands
A spring wastegate gives you one boost level and no say in it. We wanted the ECU to choose the boost for every gear, pedal position and engine speed. The 9th-gen Civic ECU has no wastegate output, so we gave it one.
Learning from Honda's own turbo engine
Honda already solved this problem on the 1.5 turbo engine in the 10th-generation Civic, which uses a motorised wastegate. Before designing anything, we read that engine's factory software to see how Honda does it:
- how its 3-bar pressure sensor is read, and the limits at which the ECU declares the sensor faulty;
- how the wastegate motor is positioned, how the closed stop is learned, and how the gate is forced open when something fails;
- how a boost request becomes a wastegate position before any feedback correction is applied.
That study became the specification for what we then wrote ourselves.
The controller
The actuator is the Honda 1.5 turbo part. We built a small controller around an STM32 microcontroller and a motor driver, with our own firmware, and connected it to the car's CAN data network. Full stroke takes about a fifth of a second.
The division of labour is deliberate. The factory ECU already knows the gear, the pedal, the engine speed, the knock state and the fuelling, so it does the thinking: it calculates the gate position and broadcasts it in two new messages we added to its firmware. The controller only moves the gate and reports what it sees.
What happens when something fails
The gate opens. An open wastegate means no boost, and the car drives like a standard Civic. That is the resting state for a lost message, a jammed actuator or an implausible sensor.
The driver is also told. Controller faults are reported back to the factory ECU, which stores them as standard trouble codes and lights the check-engine lamp: lost communication, actuator fault, boost sensor fault and overboost each have their own code. A workshop with an ordinary scan tool can read them.
Tested before fitting
The controller's firmware is tested off the car before every update, including the failure cases, so a mistake shows up on a desk and not on the road.
On the car, the controller first spent 150 km connected to the network with the gate parked open and logging, without a single fault, before the ECU was allowed to command it. The ECU took control on 16 October 2026.
Where it stands
The system has been on the car and driven since October 2026 and is what holds the current 13.5 psi target. It is still being developed: the latest controller firmware is awaiting on-car confirmation, and one of the new trouble codes currently sets a second factory code alongside it. The fix for that is built and queued for the next flash.
The full car is described in the turbo Civic case study.
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