***Blackonorange's STS Turbo Build!! - Done by Speedtech Saskatoon***

Boosted Performance

^^^If you connected the wastegate to the compressor, and the boost gauge to the IM, you will not see max boost pressure. You need to connect the lower half of the wastegate direct to the IM to see max boost pressure.


Where did yo guys get the BOV vacuum source and wastegate boost source?

If the wastegate source is right at the turbo compressor, then you will not make wastegate spring pressure for boost. This is due to pressure drop across the entire system, in this case a lot of piping. So there maybe 8psi at the compressor outlet, but only 4-5psi (or less) at the IM. The wastegate should be hooked up as close to the TB as possible.

BOV must go to the IM as it uses vacuum to open. However, if the manifold vacuum is up in the -12 in/hg, then the wastegate will not open. The spring inside it (assuming it is a Tial type BOV) is rated for vacuum, and it will not open unless the set vacuum for that spring is reached.






So with the VQ, vacuum should be in the -19 to -20in/Hg (at idle fully warmed up) and the -10psi spring is optimal. It will never open if the lowest vacuum you see is -12in/Hg.

There must be vacuum leaks present, and it would explain the high idle. Exhaust leaks will not alter the a/f ratios unless they are pre O2 sensor. In this case if the OEM sensors are used on the headers, it should not make a difference.