Thread: The basics of boost control, wastegates and how to turn up the boost.

Quite often the oem feed is right on the turbo itself, which is long before the throttle plate.

i dont see any boost feed on my aviner turbo

Do you have all of the stock charge piping? The aluminum housing for the BOV? One of those things should have the boost signal for the wastegate. If not, it might be on the manifold somewhere, where it draws from the idle source, before the idle valves, which would also never see vacuum.

Hi there,

I have been reading your excellent posts regarding external wastegates and their setup:
http://www.sr20-forum.com/information-library/16477-basics-boost-control-wastegates-how-turn-up-boost.html

There is one thing I don't get. You write about electronic boost control (third example):
"The solenoid, when at rest (closed) in this configuration blocks flow to the top of the wastegate so no pressure reaches the top. This means the full boost pressure will work against the bottom of the diaphragm and the system will maintain a boost level based on the wastegate spring. If the solenoid is opened with an electrical signal then the pressure at the top and bottom of the wastegate diaphragm is equalized. With the pressures equal the wastegate spring is easily able to hold the wastegate closed so the wastegate will never open. This would allow for uncontrolled boost."
That's clear. The way I see it used. Now, when explaining, why it is better than the bleeding method (where the regulator bleeds the pressure that works against the spring), you write
that if we apply pressure to the top of the diaphragm (helping the spring), the exhaust boost pressure (operating on the valve itself) won't be able to open the wastegate either.
The thing I do not get is this: if we apply pressure to the top of the diaphragm, we only equalize pressures of top and bottom. So the forces of the pressure applied to the top is counterbalanced by the pressure on the bottom. So the top pressure cannot help balancing the exhaust pressure. What am I misunderstanding?

Thanks for your help,
Viktor

I see the confusion. Let me edit that description and that should clear up the issue. Hang on.

I've edited the text to make it much clearer as to what is happening. I should never have explained it that way. It was incorrect. When the solenoid is fully open, only the top of the diaphragm sees pressure, not both the top and the bottom. :o

Thanks for the quick reply. This means that this setup (to apply pressure to one side of the diaphragm only) is different in wiring from the old porsche setup shown in a previous post of yours.
Interestingly enough, commercial boost control systems usually do use this setup (the porsche one with applying pressure to both sides). Is there any reason why it could be any better? Why is it any better than the simple electronic bleeding type (used with internal wastegates)?

Btw,In the post in question (regarding electronic boost control schemes), there is a picture referred I cannot see.

Regards,
Viktor

I will get to answering your questions, and I will just draw the diagram from memory and re-host it. After lunch probably.

I've re-done the diagrams for the electronic boost control section and they are way better now, since they show much more about how the solenoid actually works.

The old Porsche setup is not electronic at all, so there is no wiring involved. It is a completely mechanical system.

Furthermore with my clarification you should notice that the typical EBC setup does apply pressure to both the top and the bottom of the diaphragm.

I really hope the diagrams and a little bit of re-wording I've done will help you see the pros and cons of each system. If you still have any questions, let me know.