hack/ experiment press range of MAP sensors?

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67Dart273

67Dart273

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Anyone have any idea what the non-design/ experimental/ hack vacuum pressure ranges are of typical automotive map sensors? Do any of them go into deep vac readings? A quick search (the usual google stupidity) is not much help

Not so much interested in the positive pressure end but the vacuum end

I did find this project, but unless I mis-read something, he is really really pushing the published limits of this sensor

DIY Digital Vacuum Gauge
 
How deep in the vacuum scale do you want to go? Most aftermarket MAP sensors go deep in the other direction for boost. IE 2 bar, 3 bar. But I think most will go down to full vacuum. It’s always a voltage vs pressure scale.
 
My understanding is that a 1 bar will read from 0 to 14.7 psi, absolute. So from 0 to -14.7 psi gauge at sea level.

The sensor they show in that link goes to 2.9 psi absolute, which is about 24 inhg of vacuum. A map sensor would go all the way to 0 abs, or 29.92 inhg vacuum.

A two bar can measure from -14.7 to 14.7 psi gauge, and a three bar from -14.7 to 29.4 psi.

The scale remains the same for all sensors. Full sensor voltage (typically 5v) at 0, and 0.3v at max pressure (least vac). I have no idea how linear the scale is though.
 
I want to go as deep as I can, I'm trying to put together a "budget" "low use" indicator for occasional HVAC. Anything that would read "some idea" down into 100-1000 microns with ANY degree of "we are in this ballpark." Actually as long as I can confirm it is below 1000 microns would do As you can see, 1000 microns is down into the 29.88 zone

This does not have to be anything "fancy." Some way to power it I can figure that, and if I can justify an output vs pressure curve, maybe monitor that with a fluke

Micron Chart.jpg
 
67Dart273 said:
I want to go as deep as I can, I'm trying to put together a "budget" "low use" indicator for occasional HVAC. Anything that would read "some idea" down into 100-1000 microns with ANY degree of "we are in this ballpark." Actually as long as I can confirm it is below 1000 microns would do As you can see, 1000 microns is down into the 29.88 zone

This does not have to be anything "fancy." Some way to power it I can figure that, and if I can justify an output vs pressure curve, maybe monitor that with a fluke

View attachment 1715935219
Click to expand...
Fuel tank pressure sensors are more sensitive, and show as "H2O, max tank pressures can be a bit above ambient, & I believe they read to full depression.
 
?? I did not know any fuel tanks used sensors like that.........Thanks!! These are used for what purpose, monitoring the tank vent system?
 
Modern fuel tanks are sealed and use a pressure sensor to read tank pressure/vacuum. They use a solenoid to pull the fumes in to the engine when needed. That’s why a check engine light will come on when you leave the fuel cap off.
 
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