maybe a boost leak that the crack, or whatever it may be, opens up when you hit about 18 if none of the above works.

 

Interesting.

So the stock system is a bleed based system. That is to say if both solenoids are unplugged from the harness you probably won't get much more than wastegate pressure (it should be a bit higher than wastegate due to the restrictor pill in the factory lines i believe).

For the folks still having issues....

An easy way to test the solenoids is to unplug them one at a time and see if either causes the boost to drop MORE when unplugged.. Lets say for example you unplug the secondary and your boost goes from 20psi to 18psi... then the secondary IS working fine. Now you unplug the primary and the boost stays the same... well either the primary is not functioning or the lines are plugged or something of the like.

An easy way to test the wastegate actuator is to remove the lines from the pressure source on the compressor outlet pipe and also from the port on the wastegate actuator. Run a NEW line directly from the pressure source to the actuator port. Check the boost response. Adjust the actuator preload to get a nice stable boost curve. You may be able to get a couple psi more base boost pressure by adding more preload but if it starts to creep you have gone too far and need to back it off a bit.

 

many, many thanks!

 

fixing this with a mbc seems like the wrong thing to do (tm)

 

That definitely isn't a "fix". The AP is designed to adjust things such as the boost plots, timing curves, fueling, etc, when you go to a manual boost controller that is all out the window. The car no longer controls boost, now that manual controller does.

 

That may be true, but if he is able to get the boost back to the desired level with an MBC it proves there was likely was / is something wrong with the stock boost control system.

If you got one laying around it's an effective way to rule some things in or out and buy some time while you sort out the issue.

 

question for you all, is it possible that the stock diverter valve could be limiting me to 13ish psi? i was driving with my windows down yesterday and it dawned on me that what i always thought was hearing the turbo spool (which was more audible with one piece UICP) could infact be boost leaking out instead. I've heard the stocker was leaky (hence the need to crush it in some cases), but i've never heard of any case severe enough to limit peak to only 13. just curious what others that were more knowledgeable thought.

 

I had the same exact problem with the stage 1 93 octane on the AP. I was about 17-19 psi max and felt slower. I'm stage 2 now with the pill out and i get a little over 20psi most of the time. I do believe it is the boost control system that isn't functioning correctly.

I wouldn't think the stock DV would be limiting to 13 psi. I think it leaks at around 25 psi.. there is a good video of the test out there somewhere