Yeah. This is kinda where I am headed with the OP's issues. We should start from scratch and narrow down the possibilities.

I mean assuming there are absolutely no boost leaks. Assuming that the lines are routed and hooked up properly and tightly secured, and etc.

Assuming that the WGA was actually provided with the spring that was requested by the buyer.

Assuming the above as well as a properly functioning MBC. We are left with two general possibilities. Either the WGA is at fault. Or the MBC is at fault. Although there is also the slight chance that the DV may be influencing the issue.

The first thing that I always do in these situations is try to narrow down the possibilities and eliminate possible causes.

It is easiest, at least for me it is, to hook the actuator up directly to the boost reference source leaving the MBC out of the equation for the time being.

 

Well if there isn't enough preload on the wg and it is opening way to early if he has turned the mbc to x level and it is only reading 20 psi then it all makes since.

 

I am not sure which Forge actuator type we are dealing with in this case(piston, or diaphragm). And I am not exactly sure how they determine the spring rate either.

But, the way I see it it is misleading to label spring rate as a range between 19-24 PSI. I mean the rate is either 19 pounds, or it is 24 pounds....not both. It either opens at 19 pounds or it doesn't. Not either/or.

Most likely my confusion is due to a lack of knowledge about the particular Forge unit in question. Sorry guys.

 

Could be adjustable between 19, 20, 21, 22, 23, 24. But yeah need more info I guess to help with your confusion. Unless it is a external wg. Maybe the O.P. can verify this to help.

 

Yeah, just because Forge, or FP for that matter states that a particular actuator opens at a certain PSI doesn't always mean that it actually does under all circumstances.

I have had FP 18 PSI units that actually open at 14 PSI. And when they say 18 PSI, does that mean that it just starts to crack, or lift off its seat at 18 PSI, or that it is full open at 18 PSI?

It's best as you note to eliminate the MBC from the equation(disconnect it temporarily). Run a hose directly from the nipple on the compressor discharge tube to the nipple on the WGA. Loosen and adjust the turnbuckle on the end of the threaded actuator rod until it slides on and off the peg on the flapper valve's pivot arm. This determines true base waste gate pressure. Then incrementally rotate the turnbuckle inward clockwise which shortens the overall length of the actuator rod to a level that is just about 3-4 PSI below your target boost level. Then adjust the boost up the rest of the way via the knob on the MBC after reconnecting it.

 

The Forge units that I have had experience with were the diaphragm type for an VIII turbo. But, it did not work just the way I wanted it to right out of the box. I had to cut off a few of the threads on the actuator rod as it was too long for my particular application.

Being that it was too long it didn't allow me to preload the wastegate nearly as much as I wanted to. Being too long might in this case create early opening of the flapper valve. Because even though the actuator may have an 18 PSI(or whatever) PSI spring, if the rod is too long you'll never get it setup and preloaded to 18 PSI.

 

Yeah it is suppose to fully open at 18 psi

 

Let me give you an idea. Do as I outlined above and cursedsm suggested in an earlier post. Disconnect your MBC. In the process be sure to plug off any open hose ends or nipples that are unused.

Run a length of hose from the WGA to the J pipe nipple. Now adjust the turnbuckle to its loosest setting where it freely slides on and off the peg on the pivot arm. Take it out for a test spin and see how high it boosts at base WG pressure.

Now shorten the overall length of the rod by rotating the turnbuckle inward clockwise a few turns and retest the boost level. Then do it one turn at a time until you get it up to about 19-20 PSI. Finally reconnect your MBC and using its adjustment knob, crank the boost up the rest of the way to your target level of 25 PSI.

EDIT: If the above method doesn't work for you then I would go back to your old MBC and old WGA. Or in other words....whatever works. I have been tinkering and fiddling with adjustable actuators since before 1987 when we messed around with my first Buick Turbo Regal and a series of Garrett turbochargers on it.

Way before that I had a 1975 2002 BMW factory turbo with a KKK on it which we later swapped for an IHI RHB6 which had an adjustable actuator in addition to the factory compressor bypass valve. Yeah, a compressor bypass valve is how the BMW factory controlled boost on the KKK turbo back in those days w/o a waste gate of any sort. Needless to say I ended up disabling the compressor bypass valve.

A compressor bypass valve per se can limit manifold pressure but it doesn't slow the turbo from spinning faster. So, shaft speeds can get way high. But, this is another story altogether. Sorry for the digression.