Cannot get MAP boost to read correctly.

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AdyH
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Cannot get MAP boost to read correctly.

Postby AdyH » Wed Feb 17, 2021 5:07 pm

I have Adc 2 connected to an existing 2.5bar Bosch MAP sensor. I want the display to only show boost not vac. The values I have inputted are 0.3v at -0.8bar and 4.65v at +1.5bar. These were obtained from the Bosch data sheet. The UTCOMP calculator gave a= 0.53 and b= -0.96. With the engine off, the display shows 0 psi as it should, but with the engine running the display shows 7 or 8 psi . The engine creates no boost at idle and my ECU which is using the same MAP sensor is showing 48kpa (absolute), so why is the UTCOMP showing this boost pressure?. Am I using the correct figures ?
Thanks

ArT
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Re: Cannot get MAP boost to read correctly.

Postby ArT » Thu Feb 18, 2021 10:41 am

Could you check what voltage level is on MAP signal when you have -0,8bar or 1,5bar? I think these values from datasheet may be not correct. And do you mean -0,8bar where reference point is atmospheric pressure? Which value was atmospheric pressure, 1,0 bar or lower? We need absolute pressure for scaling, not relative.

You cna also check your readings from ECU and scale using these values, e.g. when your ecu shows 48kpa (absolute) what voltage do you have on MAP signal? You will also need second value for scaling (sensor is linear)

AdyH
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Re: Cannot get MAP boost to read correctly.

Postby AdyH » Thu Feb 18, 2021 1:25 pm

The voltage in the UTCOMP readings are 1.86v at atmosphere, engine off (1bar absolute) and 0.85v at 48kpa absolute with the engine running at idle. I have enclosed the data sheet for this MAP sensor.The sensor will output 4.65v at 250kpa absolute (150kpa,1.5bar relative to atmosphere). I did check the sensor with vac and pressure when I calibrated it for the ECU, and the figures are correct to the datasheet. The voltages the UTCOMP is reading are correct for the pressure/vac at the engine. With the engine off the display shows a correct figure of 0 psi (atmosphere). With the engine at idle the display shows 7 or 8 psi. If this figure was shown as -8psi it would probably be correct. Is this the problem ?. Will the display not show a minus ?.
Ideally I would like the display to read 0 psi for all situations that do not produce boost (positive pressure), but if I have to have a negative psi for vac that will be ok.
Also it would be nice if we had a symbol on the display for Boost. It does not seem to have one.
Thanks
Attachments
MAP.jpg
MAP.jpg (74.41 KiB) Viewed 1298 times

ArT
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Re: Cannot get MAP boost to read correctly.

Postby ArT » Tue Feb 23, 2021 10:42 am

It should show additional "VAC" icon when value in BAR is negative.
Probably you are right and it's missing minus for PSI.
Could you change units to BAR and check what it shows?

AdyH
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Re: Cannot get MAP boost to read correctly.

Postby AdyH » Tue Feb 23, 2021 11:52 am

I want to use PSI for my boost and Oil Pressure, not BAR. The UTCOMP is claimed to support units of BAR and PSI. Is there no way of making boost read correctly with PSI ?.
Is this a bug in the software that needs addressing ?
Thanks

ArT
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Re: Cannot get MAP boost to read correctly.

Postby ArT » Tue Feb 23, 2021 12:26 pm

I know I know, just kindly ask you to test it with BAR ti find where is the issue - what values does it show as BAR? :)


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