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How the ECU reads Boost...MAP sensor Q

Old 06-10-2004, 09:16 PM
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1.5 BAR
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Default How the ECU reads Boost...MAP sensor Q

Does the ECU automatically calibrate itself to detect ambient air pressure at different elevation levels? For instance, at sea level atmospheric pressure is 14.7
PSI. In colorado, atmospheric pressure is 12.2. SO, would the ECU/MAP sensor (in colorado) see 2.5 PSI of boost as Atmospheric since 12.2 + 2.5 = 14.7? or does it know what ambient is, and adjust?
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Old 06-10-2004, 09:20 PM
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Default Re:How the ECU reads Boost...MAP sensor Q

No.

It reads in _Absolute_ pressure.

Different elevations, will obviously use different MAP values, which is why there are parts on the a fuel/ignition map that you'll never use.

This would be easier to show you with a datalog map trace.
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Old 06-10-2004, 09:36 PM
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Default Re:How the ECU reads Boost...MAP sensor Q

Originally Posted by TurboEF9
No.

It reads in _Absolute_ pressure.

Different elevations, will obviously use different MAP values, which is why there are parts on the a fuel/ignition map that you'll never use.

This would be easier to show you with a datalog map trace.
ahh hah! i thought the sensors were absolute. i was arguing with someone earlier about that guess i was right
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Old 06-10-2004, 09:48 PM
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Default Re:How the ECU reads Boost...MAP sensor Q

I don't get it...so let's just say this. In uberdata, it shows in/hg and PSI. I believe someone on the uberdata forum told me the formula used was any value above 1000 mBar was converted to PSI, and any value below 1000mbar was converted to in/hg. SO, would this mean that in UD (assuming i am still in colorado), when i am at 2.5 PSI + 12.2 PSI atmospheric, then UD would show I was at atmospheric (0 PSI) due to it's conversion factors? (will post in UD forum also)
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Old 06-10-2004, 09:51 PM
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Default Re:How the ECU reads Boost...MAP sensor Q

Originally Posted by street_kings
I don't get it...so let's just say this. In uberdata, it shows in/hg and PSI. I believe someone on the uberdata forum told me the formula used was any value above 1000 mBar was converted to PSI, and any value below 1000mbar was converted to in/hg. SO, would this mean that in UD (assuming i am still in colorado), when i am at 2.5 PSI + 12.2 PSI atmospheric, then UD would show I was at atmospheric (0 PSI) due to it's conversion factors? (will post in UD forum also)

basically yes; at high altitude if you push 3psi of boost (going by the boost gauge that reads relative) you'll be slightly over 1 bar(ometric pressure unit or sea level)/1000mbar of pressure goign into the engine
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Old 06-10-2004, 09:58 PM
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Default Re:How the ECU reads Boost...MAP sensor Q

that makes sense. ------- altitude. I think i'm gonna take a reading from my MAP sensor using uberdata and try to write a scalar script to reflect the right Boost level (i.e. if at ambient the MAP reads 850 mbar, then tell uberdata to display anything >850 mBar as boost and convert to PSI)

Thanks!
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