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Map Sensor Reading Wrong-Help

 
Old 09-03-2018, 12:24 PM
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Default Map Sensor Reading Wrong-Help

Hey,

I have a MS1 PNP with the MPX4250 map sensor with 1.6 engine. I have tee'd off at the FPR and that line to the ecu, also tee'd into this line for my boost gauge. What i find is that it reads lower then what atmospheric is, for example today i have a log where it shows the barometer reading as 88 so i assume this is the initial map reading it registered with key in ON position but the atmospheric pressure in my area is 102kpa. Also i did a pull and my digital boost gauge registered and max boost reading of 11.4psi but the log registered and max kpa of 165 or 9.5psi for the same pull. So 102-88=14 or 2 psi. Boost gauge showed .20psi when key was in ON position if that means anything, sometimes i see 0.00 as well.

Can this mess up my tune and fueling? Ecu only fuels for 9.5psi but engine actually gets 11.4psi?

Should i try and set up my map lines different to fix the reading? Replace the sensor?

Thanks in advance!
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Old 09-03-2018, 01:24 PM
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Make sure your ECU is calibrated for the sensor you have first, before trying to swap the sensor. It sounds like it may be calibrated for a different sensor.
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Originally Posted by ninerwfo View Post
The “into to megasquirt thread” mentions that the MS3 basic has 5 inputs with built in pull up resistors - and I was just wondering why it would have so many, while the MS3Pro PnP has just 2 (with no pull ups?)
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Old 09-03-2018, 07:11 PM
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I have selected 250kpa for map type in engine constants, and in project properties selected the mpx4250 default option. Thanks for your reply!

Might be worth mentioning, the previous owner of this ecu i did see some of his old logs and his barometer reading was 96, so closer to ambient where we live.
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Old 09-11-2018, 08:47 PM
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Hey Reverant,

From your experience is it normal for these to read low, or maybe get worse over time? I am most likely replacing mine but just want to know what to expect from a new one. Should it be 100% accurate from the get go?

Or if anybody else knows about these sensors, feel free to comment.

Thanks in advance.
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