I have a tial sport wastegate right now with a 9lb spring. I'm running just under 12 psi with a Turbo XS MBC in the vac line going into the side port on the wastegate. I am told when I hook my Greddy Profec B II up I need to run it in another vac line to the top port. Can anyone explain why a manual boost controller is OK in the side port, but when using an electronic one you need to put it to the top? Thanks in advance

 

bump

 

i've always wondered this too.

 

I've been researching, and still don't know much. I don't know why but I would assume both lines would make for a quicker and more precise dump. I ran onto a picture a couple of minutes ago ( http://sportsnimports.com/rotm/ ) where it looks like the bottom vac line dumps back into the charge tubing. Anyone confirm this? or explain? thanks!

 

the bottom portion of the diaphragm housing is used as a vacuum ref.
this port needs to be fed with a direct connection to a vacuum/pressure source. we prefer to use the intake manifold, as this is the same source as the MAP. this allows for a bit quicker spool from what we've seen, as it pulls a vacuum on the bottom of the diaphragm and keeps the valve from opening prematurely when transitioning into pressure.

the top portion of the diaphragm housing requires a pressure source.
this port will be fed from the boost controller valve, placed inline of the same source as the bottom line.
basically the boost control valve will bleed excess pressure to the top of the diaphragm, to aid the spring in keeping the valve closed for a longer period of time. this allows the turbine section to use more of the exhaust gas and continue to spool the compressor section.
hope this clears things up a bit

 

thank you, as I'd expected only with an explanation.