So I am running a CX Racing hotside to a single On3 T4 88mm. Kit uses two generic CXRacing 46mm wastegates w/7lb springs. Wastegates will be upgraded over time. Just cleaning everything up and getting a base tune in the car.

Currently have the boost referenced from a port on the turbo cover, T'd off to each lower port of the wastegates. This will net me just a bit over 7lbs consistently.

Everything ran amazingly well at 7lbs, so I purchased a Turbosmart manual boost controller to start cranking it up and tuning the higher MAP areas.

This is where I am confused. From what I have read during my studying on the subject, the lower ports should always see what the turbo sees, and the top ports are used for boost controllers, to basically be able to apply up to the same amount of pressure to the top of the spring, effectively doubling the pressure capabilities of the springs.

So I ran a T off the line coming off of the turbo cover. One side headed to the T going to the lower ports, and the other side of the T headed into the BC. Outlet of the BC T'd off to the top ports of each wastegate. Added a generic picture I found online as a reference.

Suffice to say, this did not work. Boost controller closed, I saw less than 7lbs of boost. Opened up a few turns and saw my normal +7lbs. Opened up a few more turns with zero additional boost.

Back to the drawing board, I opened the top ports up to the atmosphere again, and this time added the BC inline with the turbo port line. Outlet going to the T headed into the lower wastegate ports. This gave me 15lbs with merely 3-4 clicks of the controller.

Can anyone shed some light on this for me? 15lbs runs great right now. Time will tell if I end up wanting more out of it. I will be upgrading to name brand wastegates before I go any further with the car and I will be trading in the rubber vacuum line I have been using for 4an braided stuff that I have laying around in mass quantity from another build. If I can get an understanding of why exactly its working the way it is, I will be much more comfortable going forward with everything.

 

Following for my build

 

the turbo smart manual boost controller I think you have is nothing more then a controlled leak in the wastegate line or bleed type boost controller. these have to go between the turbo and the lower wastegate line. these are effective but only to about double spring pressure or less depending on backpressure. the way you have it is about the best that type of controller is gonna give.

 

I have run these and a manual set up that would do what your example works like but that picture is for an electronic set which in my opinion you should seriously consider. it is far more tunable for traction which will become a limiting factor for you if it isn't already.

 

Okay. So if im understanding correctly, that bleed type is basically relieving pressure sent to the wastegates by way of opening the valve. So than normal max spring pressure of 7lbs, opening up the vent would show the wastegates their max "7lbs" at a higher pressure determined by how far open.

Wastegates will still eventually open at "7lbs", but in reality they are opening at between 7lbs and 15lbs dependent upon how open the vent is.

 

that is correct. it also can slow boost response above the 7psi spring pressure because backpressure will start to push the wastegate open once it reaches a certain pressure. in my opinion this is the least desirable way to control boost pressure. im sure someone will say it works great but it has draw backs.

 

Jesus dude you are way over complicating this. TurboSmart has a diagram on their site for manual boost controllers. Use it. And just T the connection to the wastegates together.