When I got the Forge WGA installed my tuner was having problems tuning the boost for some reason and recommended installing the forge MBC. Once that was installed, the boost was stable enough for him to tune the car. Now I'm going to start self tuning soon and would like to control the boost through the ECU. I don't want to run into the same problems my tuner had by switching back to the stock solenoid. So my question is would running the Perrin 3 port solenoid help keep the boost stable enough for me tune through the ECU or should I just keep it the way it is?

 

What exactly was the problem he was having? The Forge WGA doesn't come pre-set from the factory, so if overboosting was the problem he should taken out some preload, an MBC isn't necessary. And running the Perrin 3-port shouldn't be a problem as long as you can tune for it.

 

According to him there was too much boost and he wasn't able to control it through the ecu. Also they had taken out all of the preload from the spring and he still had issues. They ended up putting the forge mbc and the boost was still high, so they set it to it's lowest setting but I still boost to 25. So he tuned the car for 25 psi of boost.

 

Just a side note. My boost pill is a subaru wrx sti boost pill that he was able to provide because I had taken out my boost pill since I heard it would yield gains when I first got the car. I have a feeling that had to be a contributing factor.

 

Lower minimum boost <----------------> Higher minimum boost
Stronger signal <-----------------------> Weaker signal
Less boost spike <---------------------> More boost spike
Low WGA preload <-------------------> High WGA preload
Smaller bleed hole <------------------> Larger bleed hole
No restricter pill <---------------------> Large restricter pill

Some of these combinations can cancel each other out. Currently on my GT30 turbo with a large internal wastegate flapper I'm using this setup:
High WGA preload = +7 turns
Higher minimum boost = 25 psi (using the MBC to move up from there)

This would normally give a higher boost spike but I'm also doing these things to counter that:

Stronger Signal/No restricter pill = full vacuum line from boost source to MBC to WGA. Boost rockets up to set point with very little overshoot.
Smaller bleed hole = only needs to be small since my MBC isn't raising it much above what the WGA is set for.

I may still try a restrictor before the MBC or after the MBC depending if I feel the MBC ball and spring is getting TOO much pressure and then reduce my WGA preload to get minimum boost back to 24-25 psi.

It's all a balancing act and if you want to reduce the minimum boost levels even when your WGA is only at 1 turn preload, reducing the restrictor size or removing it completly as a test would be your next step. Likely your perfect setup is somewhere in between!

 

To the OP: your minimum boost is defined by the spring inside the wga (should be the red one in your case) and the preload. I don't see how the mbc would be any different from the 3 port solenoid, given that you know how and which tables to tune. If you want to run less than 25 psi, you should either change the spring or decrease the preload. My opinion is that 25 psi is a very nice number to run (good power and still very safe), i would never want to run less than that. O'wise, get a subaru

GL