Does cooler weather and less humidity produce lower MAP readings than when there is more humidity or warmer weather?
I noticed since the air has gotten cooler and less humidity, my map KPA has dropped about 3-4 KPA at idle from 53-54 to 50-51.
Is it because the cooler air is more condensed or something may be wrong?
Or is MAP KPA mostly affected by spark timing?
Last edited by STR8BALLN; 11-24-2013 at 12:35 PM.
Cooler weather shows up mostly in IAT, thus indirectly affecting Manifold Aircharge Temp. MAP might be lower on more humid days, as the rain tends to come on transitions from higher to lower pressures. It is NOT directly affecting the temperatures, unless you count rain clouds obscuring the Sun.
Yes, the idle MAP will drop a bit with colder (read: denser) air, as you can get the same amount of airflow/airmass out of smaller MAP due to increased MAT.
Idle MAP model is complicated. Yes, spark affects it, but so do a lot of other factors.
Great post thanksOriginally Posted by redhardsupra
"Good air" has more density so for the same cylinder mass
charge a lesser MAP is needed. Humidity bends the air
density some, from "nominal".
If you are in a closed loop situation (idle @ RPM, or even
cruise @ MPH) you need less pressure when the air is
higher density.
Thanks Jimmy
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