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sjf911 sjf911 is offline
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Join Date: Dec 2006
Location: Idaho
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I was finally able to get a first log yesterday after having to wait about 30 minutes after shut down picking up my son from baseball practice. It was a relatively short drive home at no more than 40mph.

Compressed view of the entire drive.

This shows the Ford MAF IAT reading on the left and the difference between the Ford IAT and external ambient on the right.

This is the Ford IAT again on the left with the true IAT signal on right. You can see where the relay switches between external and internal sensors at 5 minutes.

The left graph shows the difference between the primary signal and external ambient while the right shows the difference between the MAF IAT sensor and external. Again, the sudden change at 5 minutes is the relay switching between external and internal sensors.

This is the IC core temperature on the left with the MAF IAT on the right.

Engine bay (pre-fan) on the left with the difference between engine bay and external ambient on the right.

So, it looks like the IC core and MAF IAT cool down relatively quickly and are at about ambient between 4 and 5 minutes. The MAT sensor, on the other hand, is still substantially warmer than ambient when we finally see the real signal at 5 minutes and it has not reached thermal equilibrium by the time the log ends at about 12 minutes.

The MAT sensor is a GM open element sensor set in a bung on the throttle body adapter so there is a lot of metal without much airflow. The Ford MAF, on the other hand, has a much smaller sensor that sits more centrally in the tubing with much less metal directly around it. Also, the tubing that the Ford sensor sits in is one piece with the outflow side of the IC so is cooled, in effect, by the IC.
Sapere aude
1983 3.4L 911SC turbo. Sold

Last edited by sjf911; 05-18-2013 at 10:05 PM..
Old 05-18-2013, 09:53 PM
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