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Freescale MPX4250AP MAP sensor support

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Freescale MPX4250AP MAP sensor support

Postby Robcio » Thu Jun 01, 2006 1:21 am

Could you add support for the MAP sensor mentioned in the subject in your next software release. It is relatively inexpensive, ~$18 and should be good enough since Megasquirt uses it as its default MAP sensor.

Thanks.

Digikey part number:
MPX4250AP-ND

datasheet:
http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250A.pdf
Last edited by Robcio on Wed Jun 07, 2006 7:58 am, edited 1 time in total.
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Postby tlcoll1 » Fri Jun 02, 2006 7:09 pm

Ok.

Tom
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Postby Ivan_C » Fri Jun 02, 2006 9:09 pm

I don't see it in the pdf, but does this sensor support vacuum? It shows 2.9-36.3 psi or am I missing something?

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Postby Robcio » Wed Jun 07, 2006 7:58 am

The short answer is yes.

This sensor reads absolute pressure not gauge pressure. In order for it to be in sync with your mechanical boost gauge you would have to subtract atmospheric pressure ~14.7psi (or less depending on your location). Therefore, its actual gauge pressure range is from -11.8psi to +21.6psi.

It would be great if ECU+ could sample local atmospheric pressure at boot time, before the engine is started, and then subtract this value from the sensor readings while logging. This way, the mechanical boost gauges(which always true themselves to zero) should be in sync with the readings from the MAP sensor.

Tom would this be possible? If so, could you add it to your to-do list? :)

Thanks for adding support for the sensor.
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Postby honki24 » Wed Jun 07, 2006 11:45 am

Robcio wrote:Therefore, its actual gauge pressure range is from -11.8psi to +21.6psi.


... only sounds helpful at stock boost level? It would max out on my 24...
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Postby Robcio » Wed Jun 07, 2006 1:23 pm

Here you go if you need one with higher pressure ratings:


http://www.freescale.com/webapp/sps/site/taxonomy.jsp?nodeId=02WcbfCjB1yZQ3tKGF8716
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Postby tlcoll1 » Wed Jun 07, 2006 6:11 pm

Robcio wrote:It would be great if ECU+ could sample local atmospheric pressure at boot time, before the engine is started, and then subtract this value from the sensor readings while logging. This way, the mechanical boost gauges(which always true themselves to zero) should be in sync with the readings from the MAP sensor.

That's an interesting idea, and one that I hadn't considered. It would eliminate one of the error sources from the pressure reading, and as long as you didn't drive too far, altitude-wise, in-between data logs you'd be right on.

Do you know for sure that that's how mechanical boost gauges do it?

Tom
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Postby tlcoll1 » Sat Jul 15, 2006 9:50 pm

Ok, software to support the MPX4250A is now in, and will be in the software release after next. (The next software release, due really soon, just fixes a few bugs).

Tom
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