I wouldnt rule out taking a second look at the BC anyways. If all of the obvious typical areas seems to check out then it wont hurt taking a look at everything else even if you dont think any of it has changed. I said the same thing when my boost was dropping off, I couldnt find a leak for the life of me... changed the BC that was working fine the day before just for the fun of it... problem solved

 

Sounds like the BC is either bad or the WG arm isn't adjusted properly thus not allowing the WG to close all the way. I had the same problem with my DSM, and I was only getting about 5psi of boost by 6k rpm. I adjusted my WG arm down quite a bit and was hitting 16psi by 4500rpms. Then I changed my BC and got 20 out of it. I know when I was working with my AEM TRUBoost I had to adjust the WG spring in the settings of the EBC for my turbo to spool up a little faster, but it spiked harder. I spent about 20 minutes adjusting that one setting before I got it right. Not sure about yours but that might be somewhat of the same problem if you are able to adjust that with your EBC

 

Either tomorrow or wednesday the evo will go on the dyno for trouble shooting @ cobb and Calvin will work his magic to figure out what exactly is wrong. From all the crap thats being said and done to it, it is most likely the wga flapper thats messed up and its obvious it isnt closing all the way thus letting boost out. Along with that it could be the GM 3port as well but we are bound to find it out in a day or two.

 

I would look into the wga. I would make sure that it didn't come loose or the lock nut didn't unscrew or something stupid like that.

 

The lock up nut on the actuator rod has no effect whether it is loose or tight as long as the the rod is secured onto the flapper valve's pivot arm by the cotter pin.

 

It's actually a C-clip on MAP's WGA rather than a pin.

 

Thanks, Kracka. I thought that we were dealing with a stock turbo. Obviously, I am not familiar with the MAP turbos. I'd like to see one though.

 

I'm aware of that but what I am getting at is if it is loose and forgot to get tightened down it had a chance of being moved as it was getting preload.

 

Yeah, the actuator rod may have been tinkered with and when it was off if the backup nut was not secured against the turnbuckle then the turnbuckle may have rotated. I never thought of that. You make a good point.

 

I learned that the hard way only reason why I brought it up hahaha. I had very little preload on the turbo and it didn't start spooling till 5k.

 

I have learned to live without the backup nut on the actuator rod. It is pretty much superfluous and merely serves as a place keeping device. If you are going to be running serious preload then you have to remove it because after you cut enough threads off the actuator rod then the backup nut doesn't allow enough clockwise free travel for the turnbuckle at preload levels over 22-23 PSI depending on the brand or style of WGA. It is a good safety device though in that it allows for repeatability.

If you are going to run w/o it then you need to be extremely careful to be sure and retest the boost level realtime after making any adjustments to the WGA or the MBC. But, it is always best to test after tinkering anyway even with the backup nut on there. I have actually messed up my boost levels more by being careless with my MBC adjustments.