Yeah, 22-23 PSI spring pressure should get you up above the inherent spike in the 18 pound actuator. Also, 22 PSI of spring pressure should be just about ideal for running 25+ PSI peak boost level.

We'll just have to wait and see what happens to the 3 PSI of creep that you were experiencing once you raise the level of preload. I doubt that the FP actuator is causing the boost creep anyway. It usually can be traced to some other cause such as, for example: dump tube diameter being too small, opening in dump flange too small, waste gate bypass port in the turbine housing needs porting.

 

Ok so I removed the locking nut and screwed the eyelid down the whole way. It is now making 18psi at the manifold and coming on much harder. The creep seems to be resolved. So pending checking boost curves on the dyno with 28psi wound into it things should hopefully be sweet now!

 

This is good news for it sounds as though things have improved. However, since you are going to be running 28 PSI peak then I would preload the gate up to somewhere in the 21-23 PSI range. At least I would try it. I think that the sweet spot will be right about 21.5-23.5 PSI of spring pressure.

To achieve those levels of gate pressure you are going to have to cut two to three threads off the tip of the actuator rod though. Two to three threads equates to 3/8 of an inch linear measurement. Don't cut off any more than that though. 3/8 inch should be just about right.

I realize that it seems spooky to cut length off the tip of the actuator rod, but it is not that radical at all. If you think about it, you are currently at 18 PSI with the eyelet turned all the way down(no back-up nut). So, your current 18 PSI adjustment would still be achievable even after shortening the rod. In fact, the lowest achievable spring pressure level would still be about 14 PSI. It is just that the actuator rod's original length is just too long for your particular application as delivered from FP.

Your current level of 18 PSI would just be closer to the center of the adjustment range than it is now. At present, 18 PSI the highest preload level available to you. If you cut 3/8 inch off the tip you would still be able to return preload level all the way back down to 14 PSI if so desired. Cutting the rod increases upward adjustment that's all. You would be gaining upward adjustability while still being able to lower the level of spring pressure back down to stock levels.

EDIT: You may be asking yourself why FP would design and deliver that 18 PSI HD IX actuator fitted to your turbo and not have it setup with the proper adjustment as to actuator rod length etc.

This is simple. These actuators are designed as adjustable units to cover a wide range of housing combinations on the IX turbo platform. Your turbo can be configured with either the stock MHI IX compressor housing or the proprietary surge ported FP compressor housing. Depending on which compressor housing is fitted then the specific location of the mounting holes tapped into the casting are different. Also this actuator has to adjust to several(3) turbine housing sizes(9.0, 9.8, 10.5cm). So, differing combinations of the relative mounting points between the turbine and compressor housings require adjustably as to actuator rod length. So, actuator adjustability is a good thing. Also, some peeps like to run either more or less preload on the gate than other peeps do. So, by adjusting the spring level you can achieve quicker or slower turbo spool up.

As a related historical side note, the actuator rod on the original Garrett turbos fitted to the 86-87 Buick Turbo Regal and Grand National cars built by GM was not threaded. So they were fitted with fixed, or non-adjustable waste gate actuators. So, the first thing that the performance minded owners did was to cut the turnbuckle head off the actuator. Then they installed an internal threaded turnbuckle and ran a thread cutting die onto the actuator rod. Voila....adjustable waste gate actuator!

 

This is good news for it sounds as though things have improved. If you are going to be running 28 PSI peak then I would preload the gate up to somewhere in the 21-23 PSI range. At least I would try it. I think that the sweet spot will be right about 22-23 PSI of spring pressure.

To achieve that level of gate pressure you are probably going to have to cut two to three threads off the tip of the actuator rod though. Two to three threads equates to 3/8 of an inch linear measurement. Don't cut off any more than that though. 3/8 inch should be just right.

It seems spooky to cut length off the tip of the actuator rod, but it is not that radical at all. If you think about it you are now at 18 PSI with the eyelet turned all the way down(no back-up nut). So, your current 18 PSI adjustment would still be achievable. In fact the lowest achievable spring pressure level would still be about 14 PSI. It is just that the actuator rod in its original length is just too long for your particular application as delivered from FP.

Your current level of 18 PSI would just be closer to the center of the adjustment range than it is now. At present it is the highest preload level available to you. If you cut 3/8 inch off the tip you would still be able to return preload level back down to 14 PSI if so desired. Cutting the rod just gives you more adjustability that's all. You would just gain upward adjustability while still being able to lower the level of spring pressure back down to stock levels.