Stupid question about external wastegate install..

[empie1]

I am finally gonna install my external wastegate/recirculated 02 housing...My question is where do I run the lines? I know the one on top of the waste gate goes to the pressure source (compressor housing in my case)...and I also know that that other one goes to a boost controller, but I am not running my hks evc yet.So do I just cap that one off untill then?
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[Mr Peepers]

Connect the bottom(or side) port to your pressure source and leave the top port open. An external is hooked up "backwards" compared to a dual port internal. Oldman had a great write up on it, I'm trying to find it again.

EDIT: found it. Phew, I was worried I was going to have to type this out

Trust me Paul #1, I have done alot of research on this and I have a brand new TIAL 44 from Extreme PSI sitting right in front of me with instructions to use only the side port and VTA the top port with MBC, on the top of the instruction sheet there is a *NOTE* For electronic boost controller installation, use the manufacture's instruction.

Let's break it down into different situations for better understanding.

1. With both ports open, much like leave the fitting on an internal wastegate fitting open, the wastegate is suppose to hold approximately 2x the spring pressure (its ability to hold back exhaust pressure). Example, 14psi spring = 28ish psi of intake pressure.

2. No boost controllers but both top and bottom connected to straight intake pressure, the result is the same as #1, 28psi.

3. No boost controller but with side port connected to intake pressure signal and top port VTA, much like running no MBC with an internal wastegate, the wastegate will hold exact the spring pressure. Example 14psi spring = 14 psi of intake pressure.

4. EBC or bleeder MBC, side port sees intake pressure (which will result in #3), the outlet of EBC or bleeder connects to the top port, for every psi the top port sees, there is one PSI increase in intake pressure. Note, a bleeder MBC will work in reverse in adjustment as in an internal gate environment, the more pressure you bleed off, the less the top port sees, the lower the boost level.

5. Ball/spring MBC, top port VTA and outlet of MBC connects to the side port. No pressure will be sent to the side port until the spring pressure in the MBC is overcomed, just like an internal setup. The reaon a ball/spring MBC doesn't work with the top port is because you have no control over exactly how much pressure to send, either you get nothing or you get everything, unlike an EBC or bleeder MBC. Let's put it in examples of running a ball and spring mbc using the TIAL instruction, assuming the wastegate spring pressure is 14psi.

A. MBC all the way out (no pressure on the ball), top and bottom port sees the same pressure, you get #2, 28psi.

B. MBC all the way in (max pressure on the ball), nothing gets sent to the top port, you get #3, 14psi.

So far so good but the problem is contolling boost pressure in between.

C. MBC set to anything between 0-14psi, as soon as the ball gives, the top port will immediately see the same pressure as the side port, you'll always get #2, 28psi.

D. MBC set to anything 14psi+, the top port will never see anything at all because the side port will open the wastegate before the ball is overcome, you'll always get #3, 14psi.

Hope my explanation isn't too confusing.

Lastly, to get away with using a smaller wastegate spring while trying to run higher pressure, you leave the side port open, 28psi, then for every psi you add to the top port, you get 2psi more in intake pressure.

Many thanks to Oldman

To simply get it to act like the wastegates we are all use to, use only the bottom port whether its with a MBC or not, and leave the top port open.

 

[empie1]

But wouldnt leaving it open create a leak?

 

[Mr Peepers]

No, the top and side ports are on two different sides of the diaphragm.

The side port goes to the bottom portion of the diaphragm, the top goes to the top. When the side port is pressurized, it lifts the plunger from its seat and allows exhaust gas to pass through the wastegate. The top port would only be used when you are having problems with it blowing open.

Some more info on using both ports: http://www.dsmtuners.com/forums/tur...h-external-wastegate-ports.html#post151169306

 

[empie1]

Wow..thanks a lot!