Boost Controller Plumbing? (Externally Gated)

[brando132]

Ok, I'm in the process of installing my Greddy Profec OLED controller and I've run into conflicting information regarding external WG setups as well as some confusion on my part.

The stock setup has the boost pressure feeding directly to the wastegates, only cutting/bleeding off the supply once the desired pressure is achieved, which allows for boost creep. No thanks.
ex: http://z32.wikispaces.com/file/view/TT_ ... roller.png

I've also seen setups mainly used for internal WG that involve a MBC/EBC boost stopping the boost from reaching the wastegates until it reaches a certain level, then letting it through(duty cycles and whatnot) to activate the gates, limiting boost. Makes sense.

However I've seen different diagrams on other forums for this car as well as many others, ex: http://www.aus300zx.com/forum/showpost. ... ostcount=3
Diagramming a method using the NC port and several tees. From what I've garnered in the last 6 hours of research, this is the superior method for external WG's, as well as the method described in the Greddy manual. Why is it? Couldn't tell you. This is where the confusion on my part comes in.

Ok fine, I'll use the second one then. But wait, how does this setup actually work? Based off the diagram, boost pressure is fed to the lower port(hold open) of the WG, I'm following so far. The boost pressure is also fed to the NC port on the solenoid, then the COM port feeds to the top port(hold closed) of the WG. What?

To put it in the simplest term I can based on my(probably incorrect) understanding, below the boost threshold it feeds only to the side to open the WG and above set boost it feeds equally to both, negating the effect and causes it to work off spring pressure, won't this just mean I will be getting the spring pressure that is in my WG's?

How does this allow higher boost levels? Why is it superior? It seems to allow for unsatisfactory levels of boost creep as well. I must be missing something, otherwise it wouldn't be recommended in the manual.

Hopefully someone with experience with last setup can chime in and correct me, as I'm having a hard time finding a satisfactory answer.

Thanks for your time and answers!

[DCaff300ZX]

Yeah, this stuff is why I had my Z guy handle my 530bb install and setup as well as the ECU and such, SO much confusing info I have never been able to get my head around any of that stuff either.
Hopefully NoLimit or some others see this and chime in, I also would love to gain a better understanding of the wastegate scenario. I've also seen diagrams of altering the wastegate linkages for better correct operation as apparently (like anything else) variances can be an issue there as well.
Anton?

[brando132]

To put it in the simplest term I can based on my(probably incorrect) understanding, below the boost threshold it feeds only to the side to open the WG and above set boost it feeds equally to both, negating the effect and causes it to work off spring pressure, won't this just mean I will be getting the spring pressure that is in my WG's?

I think I understand it now. This is the correct mechanism of action but the wrong conclusion. Under the threshold it feed only to the lower port just like stock, to open the wg, but with the controller it will allow the upper port to see the pressure as well before it hits the full opening pressure. This causes the ΔP between the upper and lower to be near zero, acting as if the cars off. This means there is no force trying to open the WG except for the exhaust gasses pressing on the valve and the internal spring.

The exhaust gasses don't have nearly enough pressure to push the diaphragm open due to the path of least resistance out the exhaust. this means that once the EBC sees the correct pressure(higher than the spring pressure) it cuts flow to the upper port, causing a big change in pressure pushing the WG open. I've omitted duty cycles and gain and whatnot just to understand the basics.

Turns out my nistune board was bad, so I've sent that off for repair but I'm not expecting it to be fixed and back in the car for another month. You'll have to wait a little longer for pictures...