Wastegate control information needed

[bb]

I am in the process of installing a Wastegate on my 2.7 Turbo with the BAE kit and my custom exhaust. I have the plumbing finished for the location of the wastegate. Now I need to know a couple of things.

-The 930 Wastegate that I have has two holes in it. one on the side that open's the valve and another one on the top. What is the one on the top for.

-Where will the two hoses that go to these two holes go to on my car. I am assuming that the one on the side will go to then pressure side of the turbo near the throttle body to sense the pressure? but where does the other one go, and what is it?

-I have heard of people using MBC to control boost. What are my options so that I have some control of when the Wastegate opens, and can some one explain their operation

Thanks
Oscar

[Slant930]

The hole on the top is just a vent. It is just open to atmosphere. The other hose should go to the pressure side like you mention. On the 930's it connect to a nipple on the bottom of the intercooler. By MBC, do you manual boost controller? Typically this is only needed if one intends to run more boost than the internal wastegate spring can handle. Without that, the internal spring will control the boost level. With the MBC, it is just a valve that will restrict the sensing pressure, therefore requiring more boost before the wastegate will open.

Hope this helps and good luck.

[ssetek]

the 2 hole in the gate are pressure ports.

the lower one you usually hook up to the turbo compressor, most compressors have a 1/8 npt fitting in them for this or just drill and tap it for it , this keeps the gate reference line short,

the top one is used for a boost controller, if the spring in the gate is a .5 bar spring than it will limit you to . 5bar but if you run a boost controller than you can run .5---1.0bar with the controller, as a rule of thumb you can double your gate spring with a boost controller

[sammyg2]

A MBC does one other good thing:
It keep the wastegate from seeing any pressure until it reaches the desired set point.

most wastegates are designed so that a spring keeps em closed and positive boost pressure overcomes the spring, opening the valve and dumping exhaust pressure.
Onliest problem is, exhaust pressure acts on the wastegate spring in the same way as boost, just to a slightly lesser extent (depends on the diasmeter of the piston and valve).

Soooo..... as the exhaust pressure rises, the waste gate starts to open. As boost starts to build, it opens more. That makes the boost come on gradually and reach substantial boost levels later in the rpm range. It increases lag as well as moving up the threshold.

So you install an MBC.
It is a spring loaded device that blocks all boost pressure from getting to the waste gate until it reaches a high enough point (MBC set point) then it pops open and hits the wastegate with full boost pressure. The exhaust pressure still affects the wastegate but not that much.

I installed one on my car and it works. The boost hit like a shotgun and it hit at least 300 rpm sooner.
To install one you just plumb it in the line going from boost source to the side of the wastegate.
They are relatively cheep, you can get one on e-bay from $15 to $50 depending on name brand and bling factor.
Mine is low-bling bronze ($15 version).
An electronic boost controller is better but costs cubic dollars and is more complicated.

[bb]

Sam,
Can you post a picture of your set up?

Oscar

[sammyg2]

Sure, what exactly do you want in the picture?
The MBC is kinda buried behind the turbo inlet and outlet piping but I can take a picture of the waste gate.