So, the turbo has been installed in the car for quite some time now. I have been changing and improving things with regards to the electronics and the wastegate actuator over time and the project is almost fully working. The next few posts will detail these.

Firstly, the wastegate actuator.

I had originally make a wastegate actuator which was controlled by a hobby servo, this is described in a previous post. This was controlled by an Arduino in my piggy back engine controller using a PID loop to the manifold pressure. The mechanical side of the actuator worked quite well however I could not get the PID settings correct to maintain control of the boost pressure.

Having a bit of a think I realised my mistake. The engine controller operates to the manifold pressure, this is the pressure after the throttle butterfly which normally operates at a vacuum. Using this pressure to control the wastegate actuator was not going to work. I should have been controlling the wastegate actuator based on the pressure BEFORE the throttle butterfly valve. Otherwise when the throttle is part open, the boost pressure can build up in front of it without the actuator controller knowing. When the throttle is fully opened all of this pressure floods into the inlet manifold causing a large pressure spike. I would have to install another pressure sensor before the butterfly valve.

At the time I needed the car to work to some extent so I ordered a pressure actuated wastegate with an adjustable spring to set the maximum boost pressure. Search 'kingawa adjustable turbo actuator' on ebay. I had to modify the bracket a bit to fit my turbo but it comes with most of the stuff you need. Heres a picture:

This works nicely although it is quite hard to change the spring particularly when the exhaust system next to it is red hot.

I may revisit the electronic actuator at some point in the future.