Or the SG-IIs IAT readout display is the unadulterated RAW signal while the OAT readout is preprocessed for human consumption.

 

I would bet good odds that the FEH's hybrid engine control system uses the OAT to moderate the level of regenerative braking as the OAT declines to or near freezing.

 

Sorry... I was being overly general.

The IAT reads 10 degrees higher than ambient 96% of the time.*
It reads 2 degrees cooler 2% if the time, and 2 degrees warmer 2% of the time.
Which I will argue, is very good, and very reliable, and "good enough".

*After engine warm up to "normal".

This is far more trustworthy than any dime store ( Wal-Mart ) weather gauge.
Probably better than most Gentek or whatever aftermarket accessories as well.

 

I did find evidence that the engine control system does infer ambient air temperature for the EGR flow check entry condition. A min of 32F and max of 200F. Look at page 68 here:
http://www.motorcraftservice.com/vdi...DSM901_HEV.pdf

GaryG

 

You call 10F over OAT 96% of the time accurate and far more trustworthy than a Wal-Mart guage??? That doesn't agree with its own manual describing how the IAT value is supposed to act!

 

There's actually another page in that file that states Ambient Temperature(infered by IAT 40F-100F). IAT and OAT are very close while driving. Maybe that's when it's infered?

 

Originally Posted by wwest
I would bet good odds that the FEH's hybrid engine control system uses the OAT to moderate the level of regenerative braking as the OAT declines to or near freezing.

Data has been posted on this site disproving this statement. What part of "NOT TRUE" does he not understand.

 

#1 you are a dumb A$$.

#2 a scan tool is a generic tool, and there is no such thing as a "supposed to" that fits all vehicles.

#3 measuring OAT from a vehicle is very difficult. Do you measure it 6" off the pavement, 2 feet, 4 feet, 6 feet? Front? Back? Sunny side? Shady Side? Night? Day? You will get a different reading each time. Plus or Minus 10 degrees of variation would be very good. The fact that the FEH is consistent with the IAT to within less than this, is REMARKABLE.

#4 your "other meter, or scanner" has no better accuracy than the ScanGauge. Different features, perhaps.

#5 Whatever you are using to measure OAT is no better than a FEH's instruments.

Now, can we move on?

 

To illustrate my previous post(s)... Do this exercise ( mentally if you have the ability.... ) otherwise, go out and do it.

Install your own OAT sensor. Put it anywhere on the car you feel is best.

In short order, you will find, it works well some of the time, and works poorly some of the time.

THERE IS NO PLACE TO MOUNT SUCH A SENSOR THAT WORKS WELL UNDER ALL CONDITIONS. So why have one at all that only works some of the time?


The National Weather Service realizes the challenge of measuring outside air temperature, and has created standards to meet the challenge.

A) The thermometer must always be in the shade
B) The thermometer must always be in a white box
C) The box must always have ventilation on all 4 sides.
D) The box must have a double roof
E) The box must be at least 100 feet from pavement of any kind
F) The box must be at least 4x the distance away of the height of any nearby objects (trees, fence )
G) The box access door must face North.
H) The box must be anchored securely enough to prevent vibrations of wind or other
I) The box must not be placed on a steep slope.
J) The box should be 5 feet off the ground.

Now where are you going to mount your OAT probe on your vehicle that will meet those standards???

Change just one, and the NWS will argue you have a "false" reading.

 

#1: Can't anybody disagree with you without being called names?

#2: The SG-II manual describes basic IAT operation.

#3: Ford mounted the OAT somewhere behind the front grille.

#4: My scanner shows values as described in the SG-II manual. You have no knowledge of the accuracy of either. They should agree but they don't.

#5: Answered in #3.

You have short term memory loss! Do you smoke pot?