Wastegate feed source: vacuum or charge

I may be wrong, I'm only thinking based of physics and not experience, correct me if I'm wrong.

If you feed from before the throttle plate, at full boost (say 15 psi) when you back off the throttle sharply,
There is still pressure in the intake pipe, but vacuum in the manifold. Since the turbo is still spinning it builds pressure for a small amount, the intake is still pressurized (15+) the BOV opens , and the waste is still open, and the turbo unspools??

If you feed from behind the TB, when you back off sharply, the BOV opens to reduce excess pressure, but since the manifold is now under vacuum. The waste gate will see no pressure and close and whatever exhaust is still there will be spooling the turbo??

It makes me think that if you feed from the manifold, you will hey better response as the wastegate is closed as soon as you back off.

From your links, the guys are worried about the wastegate seeing vacuum and hurting it, can you not just put a check valve in the line so that when the TB is open, the wastegate is reading positive pressure, but when the Tb closes and is under vacuum, the check valve is closed, and the wastegate sees 0psi, and still closes as normal.
 
depends on the boost controller

option a) wastegate/s ->boost controller-> intercooler pipe

option b) wastgate/s -> boost controller ->1x hose to pre turbo suction, another to pressured pipe/manifold


oh, didnt really read it all...yeah id go from pre TB.
 
wastegate requires atmospheric pressure to open, allowing exhaust gas to bypass turbine, reducing drive pressure. if wastegate line is connected post TB you have vacuum, hence no wastegate activation leading to full pressure on both turbines in opposing directions (even for very short time with BOV present) which in turn would eventually lead to catastrophic failure of BHOPAL proportions
 
Connect the wastegate to a non vacuum boost source. Charge pipe, or generally as on factory cars and off the shelf turbo at the compressor housing. If not u can tap a npt thee!d on the housing or get a npt bung welded on the housing or nearest charge piping.

Bov needs to be connected to a vacuum source because without this the.Bov will not open.

Henry
 
Tron/brendan your understanding on how a wastegate works is wrong. Wastegate have a cracking pressure and pressure when they fully open to get exhaust gases out. They do not use vacumm for operation.

They work with a spring that keeps the flap shut.

Bov are different.
They would use a change in vacuum to open the valve.
 
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