I thought I would share the solution to my boost control problem which included a runaway over boost at takeoff and a wondering non-controlled boost in  level, climb and descent cruise flight.

 

I found through testing the wastegate did not have the capacity to bypass enough exhaust and the turbos were therefore uncontrollable. Gary at Main Turbo out of California was a huge help and found a different wastegate with the same footprint but a larger ID.  The new part arrived today, was high speed taxi tested and then flown.  The two hour flight was perfect and the problem seems to be solved.

 

I must point out I have changed several parts in the turbo system including custom intercoolers, custom tailpipes, removal of the tailpipe restrictor and my own sonic nozzles.  However, the sonic nozzles are made to the Piper Mirage inside dimensions.  I also have the large Mirage compressors, 8.5 to 1 CR and an experimental camshaft.  I am now adding a larger ID wastegate to the list.

 

Craig Berland

N7VG