Richard,
I didn't realize the 67 did not have the pop-off valve.
However, the pop-off valve does not replace the variable controller. They serve very different functions. The controller adjusts the position of the waste gate to maintain a constant "delta" in the upper deck pressure, while the pop-off valve is for overboost protection.
If the 67 doesn't have a pop-off valve, how is it protected from overboost?
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