Thanks for the post Jakob! After I read it, I went "ooooh" and immediately ordered a 4 port MAC; waiting on it to arrive. Happy to see I picked the same parts you just recommended
See, I'm hopeful that applying boost pressure to the top port will fix my current boost control issue.
Currently running boost control via a 3 port MAC, plumbed in the conventional way. It all worked on the dyno, and I started tuning the part throttle and other maps. But has since become obvious that the system doesn't seem to operate as expected under boost, and I'm confused....
Testing AUX output on the ECU (Motec), valve seems to open/close fine. Logged duty cycle shows as expected (10%) until it activates @ 130 kPa, then goes to maximum configured duty cycle (70%) and just stays there - as it is having no effect on boost). Valve is set for 25Hz, per Motec drawing.
So on the road, boost hits spring rate and just sits there with the valve running @ 70%, trying -and failing - to increase boost to target. Until you run out of road or RPM.
I just can't find any smoking gun (as in obvious boost leaks, missing plugs, blocked/split/disconnected hoses etc), so kinda scratching my head... WG is a Tial F46 with about 600 miles on it (like the rest of the motor).
Also on the way is some 6mm ID (as per Tial, to match the 1/4" barb fitting) silicon WG piping to replace the current braided cloth - as that has an ID of 5mm. Which I note is 25% smaller area.
Does it show that I'm running out of ideas/clutching at straws here? I can't imagine that this could make enough difference. Could it?
Anyone got any suggestions, ideas to try - or ever seen a similar problem?
The only theory I can come up with is that maybe WG valve guide is leaking as Jakob says - and/or hose diameter too restrictive (both MAC port 1 and Tial side port tee'd directly off the Kokeln) to keep up.
But I'm kind of struggling to believe that. Turbo seems to spool entirely normally - surely that thing is pushing a gale?