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      06-29-2008, 01:02 PM   #80
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Drives: 09 AW E92 M3 w/DCT
Join Date: Mar 2008
Location: Houston, TX.

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Originally Posted by scalbert View Post
I guess I do not see what you are disagreeing with. As you illustrated, the solenoid is bypassed thus putting continuous vacuum to the wastergate actuators
This is not what I said. Only the rear solenoid is bypassed and in this case allowing constant vacuum to be seen at the rear wastgate actuator. If it were both this would be worse.

Originally Posted by scalbert View Post
(note, as you have shown, the one vacuum line after the solenoids feeds both wastegate actuators).
This is not what is illustrated in my photos or the link you provide. It is definitely not in what I wrote. There are two accumulators. There are two accumulator hoses. In stock configuration, each accumulator hose is attached to its corresponding solenoid. In the video, hence my pictures, the only focus is on the REAR accumulator, solenoid, wastegate actuator, etc. The front system is never altered, which is the root of the problem.

Originally Posted by scalbert View Post
Perhaps the below diagram will illustrate how the vacuum line to the accumulators are fed fromt he same vacuum pump sources.
Agree. One vacuum pump. Two accumulators. What difference would this make in your point of view or mine.

Originally Posted by scalbert View Post
Secondly, it also shows how both solenoids feed both actuators; byapssing one just forces control of both turbos on one solenoid. This is contrast to what you previously alluded that only the rear turbo's actuator was affected which is clearly not the case.
This is a wrong assumption. Both solenoids do not control both actuators. The hose between the two solenoids is to balance the response of the system when the solenoids are open. Think of it more as a damper to smooth out system response. Primary control of the wastegates is from the solenoid and accumulator they are supposed to be hooked to. In the case of this bypass, the rear wastegate actuator is exposed to constant vacuum as it is hooked directly to the rear accumulator.

As I stated before, had both accumulators been Tee'd to the front solenoid, the rear would have been bypassed and full control would reside with the front solenoid. The vacuum signal would have reached the rear wastegate through the yellow hose. This setup, however, would cause significant delay in spool up for the rear turbo, hence the reason BMW designed the system the way they did.

The video clearly highlights that only connections on the rear system are altered. Look at the video and diagrams again and trace a pressure pulse through the system. Ask yourself how you would control that pulse. If you look at it from that point of view, it should become clear for you.

For the record, I know V2 & V3 no longer use the bypass. I wonder why? The point I make is that if you could make such an egregiuos error, either you have no business doing this or you look for shortcuts without exploring the full consequence. Either is too much risk for my hard earned money. If Shiv were to offer a version with warranty on damages to the car (put his money where his mouth is), this would speak volumes.