So... I may be way off here, but I'm curious if I'm not...
First, my setup...
'90 1.6 shitbox
Greddy manifold & Turbo
With this setup, the car would hit 5.5 psi and hold it fairly decently to redline. (Vacuum
I just added a front mount, nothing too huge but decent size... Its an ABD made for a MK4 1.8t.. 2" inlets, 20" or so core, blah blah blah.
After the install, the car would hit 6psi (I tightened the wastegate arm a little more than before the intercooler), then would taper off, fighting to hold 4.5 psi by redline... No big deal, I figured as much.
I had an AVCR laying around in my shed, so I figured I would throw it in and use it to up the boost and help control it better... So I installed it, running the vacuum lines from the compressor outlet to the solenoid, then to the wastegate. I tee'd into the FPR vacuum line for the AVCR boost sensor. Even with the solenoid electrical connector unplugged from the solenoid, it would spike to 14psi (To which I obviously stopped instantly)... I tried all vacuum line configurations, etc etc.
I did a bunch of research, and I read that sometimes with a small turbo, that the inner diameter of vacuum lines, as well as the length of vacuum lines can greatly affect boost. I also decided to change my boost source from the compressor outlet to one of the nipples on the throttle body. This allowed me to hold at about 10psi, and it holds very solidly with the AVCR.
My questions are this... Is there any validity to the inner diameter of vacuum line & length theory? I have different size vacuum lines on the MS, the BOV, and the AVCR... I used the crap I had laying around. I am planning on purchasing a long length of one size vacuum line, and shortening / cleaning up everything, but I'm curious about what I should setup and how.
I apologize if I'm rambling, and making no sense... But coffee hasn't kicked in yet.
Oh yeah one more thing... The vacuum ports on top of the throttle body. Are those pre-post the butterfly? Curious if I need to drill a hole in my charge pipe and use that for a boost source right before the throttle body. They look like they are post butterfly, but I don't know if they flow through the casting or something to the front side...