From newer skymasters to old?

[Richard]

How difficult is it to change something on a older skymaster to a newer idea? For instance. I have a 67 Turbo. That year has a rate of change controller. Starting from 69 on they eliminated all that crap and went with a "pop off" valve in the induction.

[stackj]

It really depends on the people in your local FSDO. A good number of the inspectors will accept a change (Field Approval) that the manufacturer considers an improvement.

Some inspectors may require that you have a DER go over the requested change and bless it off.

Some inspectors won't approve any changes. I think your best bet is to arm yourself with documentation on the old system and the new system and go talk to the inspector about it... find out what their requirements are.

Good luck.

[Kevin McDole]

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?

[Richard]

A variable controller and wastegate controller are two differant things. The variable controller serves as a pop off valve in the 67-68 skymasters. They didn't work that well, and they require 4 lines to it. From 69 on they eliminated the variable controller and went with a pop off. Modern day turbos have the wastegate controller built into the turbo housing.