I sorted the issue with my piggy back controller missing crank pulses. Turned out the UART port was sending using interrupts instead of DMA and messing things up. Now everything works well.

I installed a stronger spring in the wastegate, now set to just below .5 Bar. The car is much more powerful now and much more fun to drive. No idea what kind of HP the engine is pushing out now but it must be close to 200.

I took things easily at first as I had added some approximate values into the fuel map. Eventually I was able to get somebody to drive the car with me sitting in the passenger seat logging the boost pressure, RPM and air fuel ratio. Initially at low RPM the air fuel mixture was running a bit too lean for comfort (around 0.95 lambda). I was able to modify the fuel map to get a lambda between 0.8 to 0.85 at all RPMs (12 to 1). This only took a few runs up and down the road.

The map is set to retard the ignition timing by 1° per PSI starting around 0.15Bar. I could lower this value and potentially get more power for the same boost pressure but i would be risking detonation and destroying the engine.

I am very happy with how the project has turned out. There were times when I almost gave up with the engine controller and brought one. Bit of an emotional roller-coaster towards the end!

I have started to upload diagrams and software etc.

Tasks remaining are to tidy up the engine bay a bit and to sort out the dump valve. At the moment it doesn’t vent the inlet pressure quickly enough causing compressor surge which is noisy and becoming quite annoying.

I have booked a track day at Brands Hatch race circuit in mid December. We will see how long the engine lasts!