pressure regulators

[Bernd Felsche]

Brian Dessent tapped away at the keyboard with:
> Steve.Flanagan at VerizonWireless.com wrote:
> > looking to making a control for the waste gate that is solid state, just
> > tossing around some ideas and seeing what devices are already available.
> 
> Oh.  So you want to measure pressure and actuate a solenoid at a certain
> point.  I would start with Motorola's line of pressure sensors, have a
> look at:
> 
> http://e-www.motorola.com/brdata/PDFDB/docs/SG162.pdf
> 
> I recommend the "integrated" type because their output signal is much
> more robust and this is much easier to deal with in the extremely noisy 
> (in the electrical sense) automotive environment.
> 
> The mpx4250a reads absolute pressure from 20 to 250kPa, which
> corresponds to about 24" Hg vacuum to 21.6psi of pressure.  Yes, I think
> this is the same sensor Megasquirt uses.  I'm using it to make a
> solid-state vacuum/boost gague.  Anyway, you could use this or a similar
> one (in your case you could use a differential/gage type since you only
> care about pressure and not vacuum) and use set up a comparator to fire
> the solenoid at a certain pressure.  Or you could get more advanced and
> use PWM to slowly turn on the wastegate as opposed to an on-off deal.

I've read that some wastegates don't "like" being partly
open/closed. The control pressure is sometime used to operate an
"on-off" arrangement, not a linear actuator.
IIRC that was the motivation for VTG.

If you do want to try to modulate the wastegate, then you can use
something like an idle-air bypass to regulate the control pressure
to the wastegate servo. The bypass valves typically operate on
current - PWM or variable "constant" current. They are fairly simple
to drive.  A separate "actuator" is used as the forces required to
operate the wastegate can be quite high - too high to easily exert
by purely electro-mechanical means, but comfortable for pneumatics.

-- 
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