Author Topic: map sensor reading  (Read 10399 times)

Offline Seight-v8

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map sensor reading
« on: December 06, 2009, 05:10:46 pm »
hello all,

Should the map sensor read the same as atmospheric pressure when not connected or when engine is running.

Can only get mine to read a max of 90kpa, and it still about 10kpa out from actual pressure readings.

cheers

scott
Engine:Rover V8 4600cc
Vems Firmware:V1.2.38, GPS, SDcard, LCD & Dual lambdas, Wasted spark, 36-1 trigger, Cam Sync & Bluetooth serial.

http://www.vems.hu/wiki/index.php?page=MembersPage%2FScottRichmond

Offline Sprocket

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Re: map sensor reading
« Reply #1 on: December 06, 2009, 06:23:17 pm »
You need to calibrate the MAP sensor, and ensure it is the correct range

Offline emil@vems.se

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Re: map sensor reading
« Reply #2 on: December 06, 2009, 09:08:10 pm »
Here is map sensor calibration info from Vemstune help:
SensorCalibration scale
115kPa104kPa
250kPa250kPa
300kPa304kPa
400kPa414kPa

Set this, then if needed, adjust offset to calibrate to known barometric pressure

//Emil

Offline GintsK

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Re: map sensor reading
« Reply #3 on: December 06, 2009, 11:59:03 pm »
Here is map sensor calibration info from Vemstune help:
SensorCalibration scale
115kPa104kPa
250kPa250kPa
300kPa304kPa
400kPa414kPa

Set this, then if needed, adjust offset to calibrate to known barometric pressure

//Emil
Emil, IMHO here is errors.
My experiments and MPXH6300A datasheet gives another result: range should be 315.1 and offset 1.1.

I will check rest of datasheets and report!

Gints

Offline GintsK

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Re: map sensor reading
« Reply #4 on: December 07, 2009, 12:27:38 am »
Here is the results:

http://www.freescale.com/files/sensors/doc/data_sheet/MPX4115A.pdf

115KPa sensor: offset 10.6 range 111.1

http://www.freescale.com/files/sensors/doc/data_sheet/MPX4250A.pdf

250KPa sensor: offset 10.0 range 250.0

http://www.freescale.com/files/sensors/doc/data_sheet/MPXH6300A.pdf

300KPa sensor: offset 1.1 range 314.5

http://www.freescale.com/files/sensors/doc/data_sheet/MPXH6400A.pdf

400KPa sensor: offset 3.5 range 413.0

All four matches with results on real board by applying 0V and VCC to sensor input.

http://cache.freescale.com/files/sensors/doc/data_sheet/MPX5700.pdf

700KPa sensor: offset -31.1 (negative!) range 777.7


Calculations is done this way:

1) calculated theoretical presures at 0V supply Result is offset.

2)calculated theoretical pressure at Vsupply=Vout

3)subtracted both resulting pressures = range

Gints
« Last Edit: November 09, 2010, 09:03:40 am by GintsK »

Offline z0tya

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Re: map sensor reading
« Reply #5 on: October 23, 2010, 08:38:36 pm »
Why need to set 315.1 range when the data sheet says 20 to 304 kPa at 3 bar sensor?

Thx

Offline gox

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Re: map sensor reading
« Reply #6 on: October 23, 2010, 08:55:10 pm »
i just installed unit with 250kPa and offset is 10kPa,so its true.
E30 2.7 - VEMS,KKK K27.2,Schrick,1bar

Offline GintsK

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Re: map sensor reading
« Reply #7 on: October 24, 2010, 10:13:07 am »
Why need to set 315.1 range when the data sheet says 20 to 304 kPa at 3 bar sensor?

Thx
Range here is mathematical not physical value. Physically then range is just 304-20=284Kpa.
 But ECU calculates MAP value mathematically. datasheet give also line equation for this calculation. My values comes from there and verified on bench test.

Gints