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I was just thinking about something someone told me and wishing there were a more simple method of doing it. I also keep reading about seriously improved mileage from people who disable/remove their turbos.
So - the issue is that the turbo is effectively spinning and providing boost whenever there is insufficient vacuum to keep the CBV fully open. There is not full speed rotation, but there is some - and it is inversely related to engine rpm.
My idea is to establish vacuum, controlled by a hand-operated electrical switch (could even be a volvo dash switch!), using a cruise control vacuum pump.
I have 2 serious concerns and 2 minor doubts as to the plausibility of this design:
1) If the CBV actually closes more completely given a positive pressure rather than 0 vacuum, there needs to be a change in this (my) design. If positive pressure needs to be applied for full-speed turbo rotation, there cannot be a one-way vacuum valve between the turbo and the intake manifold.
2) If the vacuum pump were to cause problems by applying vacuum to the turbo and thereby to the rest of the manifold, there would need to be a one-way valve between the turbo and the intake manifold. (possibly causing problem 1)
On the other hand, if the CBV has no change in operation between positive pressure and no pressure or vacuum, the design seems too simple to be functional. I avoid simplicity on principle. Perhaps the minor increase in manifold pressure would be enough to cause problems given the installation of a one-way valve blocking pressure to the turbo.
Minor Doubts
1) Turning off the vac pump by hand could lead to reduced driveability in emergency situations.
2) What if the ECU finds out?! (hehe) If the ECU finds this to be a fault, could it throw a check engine light? I have seen no evidence to suggest it would.
My suggested design is at the end of the page.
If someone were really obsessed, they could set up this design x2 - one for vacuum, one for pressure, and operate them in parallel
-Will
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1990 740 Turbo, on its way to stock specs, maybe beyond
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