home / work / electronic wastegate
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. I 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 I gave it one.
The controller
I fitted a motorised wastegate actuator and built my own controller for it, running my own firmware and connected to the car's 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 sends it to the controller. 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.
Have a car the usual tools cannot touch?
Tell me the car, the engine, the gearbox and what you want it to do. I reply to every serious enquiry.