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2006 VZ 3.6LT LEO MAP sensor help

kz1000a

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Hi all, been a while since I last sought advice from the forum, but here we go again.

Pictured above is my MAP sensor. The green o-ring end fits into the red circled hole.
Once fastened in there, it appears to just go to atmosphere?
I don’t see how it can measure any pressure differential, being open to atmosphere?

I did the Mace plenum chamber riser mod some time ago and am wondering if I left something off?
Anyone able to enlighten me here?

TIA
 

lmoengnr

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MAP, Manifold Absolute Pressure, measures intake manifold vacuum.
 

Fu Manchu

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It does measure atmosphere.

That is how it is.

Uses atmosphere air pressure as part of data for ECM to control timing.
 

kz1000a

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It does measure atmosphere.

That is how it is.

Uses atmosphere air pressure as part of data for ECM to control timing.

Would it be fair to say, that if I only ever drive at sea level, then the signal I/P to ECM would be fairly constant?
But if I drove up to the “mountains”, then the signal I/P to ECM would be different?
So it is not really configured to measure the absolute pressure within the manifold?
One more question, does this particular engine employ any EGR system?
 

Fu Manchu

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No, because air pressure changes quite a lot at sea level.

Screen Shot 2020-10-27 at 6.26.11 pm.png


Screen Shot 2020-10-27 at 6.26.54 pm.png

The ECM will compare air pressure (barometric pressure) with the temp and density data from the MAF near the air filter and do timing and fuel trim adjustments to suit. A difference in 20 or 30 hPa can make for enormous differences in how the air behaves.

Air Pressure will generally also change as you go higher in elevation, though there are sometime exceptions, such as local inversions.

The same sensors are used to measure the MAP, as @Imoengnr mentioned, in other configurations. They do similar jobs with the same tool.
 

kz1000a

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Thank you Fu Manchu
Thorough explanation and additional barometric air pressure charts support your reasoning.
Air / speed density data plays a role in look up tables?

P.S. Miss the days of a 186 red motor (bored out to 192), triple SU’s / strombergs and the sound of straight cut timing gears.
 
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