wastegate configurations

[kickerzx]

i made a post on another forum but got lousy responce. so i`ll try you guys. (i`ve just copied from that other forum)

Hi folks! I need some of your thougts on wastegate configurations. I`ve got a Nissan 300zx twinturbo with external wastegates. They are hooked up as they are supposed to be according to every manuals I have found. As i understand them anyways… like this

http://i2.photobucket.com/albums/y28/kickerzx/wgbildesomdetern.jpg

The thing is. I want to run my max boost at 22-23 psi. no problem. But when the springs are adjusted so that I can achive this, the minimum of boost that I am able to run is 15 psi. this is a range that is not acceptable to me. I want to be able to run a boost of 6-9 psi at the lowest..
The reason for this poor range is obvious. I wont bother to explain to much but the bottom line is: The bottom port is working agaist the wastegate all the time so the spring rate have to be rather firm and so on..-

Now. I`ve been tinking… Are there any good reason why I cant configure like this?

http://i2.photobucket.com/albums/y28/kickerzx/wgbildebaretoppen.jpg

This way i should get a much wider boost range. I should be able to just set my boost controller at say 80% and then adjust the springs so I get the boost I want at that level. The lowest boost should now be well within my wishes.
The only downside I see with this is that the wastegates would get a slower response time because there are only the exhaust backpressure to get them open. Im not sure how bad this would be. Any thoughts?

Then there is this way of hooking them up:

http://i2.photobucket.com/albums/y28/kickerzx/wgbildebarebunnen.jpg

Here I would adjust the spring to the max boost. And let the controller work it downwards if you get my meaning.
Well….. This is really not an option. It’s a baaaaad way of doing it. Just wanted to mention it.

Then there is this:

http://i2.photobucket.com/albums/y28/kickerzx/wgbildetobcs.jpg

As I see it this should be the BEST way of doing it. It would mix the good “wastegate holding” in option 2, with the fast “opening response” from option 1
I am no sure my boostcontroller (greddy profec b spec II) is up to the task of powering two solenoids though.

do you see anything wrong with how i have done it?

Soooo… Please hit me! ;o) (with suggestions that is)

eeh NO=normaly open
NC=normaly closed
TB=throttle body
IC=intercooler
BC=boost controller

Steve

[slo360]

Put in springs that represent the lowest boost required. Run a fixed line from the turbo housings to the lower port. Use your boost controller to add boost pressure to the top port to increase boost.

Low boost threshold is set by control spring, to increase boost you add pressure into the spring chamber to increase the coil springs effective spring rate.

cheers

[kickerzx]

yeah. thats exactly as it is like right now. like the pic on top

[Galantman]

if you arent returning to the normal spring set boost pressue with setup 1, and the boost controller turned off, id say that it totally seals the top of the wastegate, which will work differently to having the top open to atmosphere. having it sealed but no "extra" pressure fed to it will increase the boost as your trying to compress the air above the diagphragm rather than just push it out of the way with no resistance.

check if you have the boost controler hooked up correctly. or that it even has the option to open to atmosphere. if not, your screwed.