I wanted to be able to control the wastegate via a servo driven via my engine controller. Normally the wastegate is operated via a pneumatic diaphragm directly from the inlet pressure. This doesn’t give you much scope to easily change the pressure setpoint however. After market 'boost controllers' are available which use a solenoid valve to bleed off some of the pressure sent to the actuator. This only give you the facility to raise the pressure setpoint over stock. I wanted the ability to lower the pressure setpoint during initial testing/tuning.

I brought a Turnigy TGY-1501MG servo rated at 15Kg/cm to do some testing. I chopped up a sab 9-3 wastegate actuator for the spring, spring seats and shaft and welded up a new bracket. My old meccano set came to the rescue providing a roller for the top of the spring seat.

The actuator worked quite well although I think this application is at the limits of the servo's torque capacity. The holding current is quite high which may cause overheating. The servo is controlled via a PWM signal from an arduino in my engine controller. Will test when I have the turbo installed on the car.