I'm putting on an EWG to help with boost spikes (and of course for other various reasons) but I'm perplexed by the plumbing recommendation from COBB (and probably others) on how to run the vacuum lines and how that works.
Here's the picture from COBB:
So in an IWG setup, port 1 goes to boost source (compressor outlet), port 3 is the bleed off back to intake and port 2 is the Wastegate.
When you add Wastegate duty cycles in the map, it effectively bleeds off some pressure back into the intake to prevent the WG arm from opening as much as it would without.
An EWG is reversed no? With the T in the diagram splitting off the boost source, the lower port (under the diaphragm) receives full boost all the time but the upper port only receives what's left after some pressure is bled off. That doesn't make sense to me, because wouldn't this make it run on spring pressure?
I can understand how the lower pressure area during boost that goes to the top port creates a sort of soft resistance to the spring but at the same time the lower port is getting even more pressure added and has the same spring force pushing right back.
Spring + boost < Negative spring + partial boost!?!? Maybe I'm just not visualizing the physics here. Maybe someone can chime in and fry my noodle.